qemu/qapi/qapi-visit-core.c

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/*
* Core Definitions for QAPI Visitor Classes
*
* Copyright (C) 2012-2016 Red Hat, Inc.
* Copyright IBM, Corp. 2011
*
* Authors:
* Anthony Liguori <aliguori@us.ibm.com>
*
* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
* See the COPYING.LIB file in the top-level directory.
*
*/
#include "qemu/osdep.h"
2016-03-14 11:01:28 +03:00
#include "qapi/error.h"
#include "qapi/qmp/qerror.h"
#include "qapi/visitor.h"
#include "qapi/visitor-impl.h"
#include "trace.h"
qapi: Add new visit_complete() function Making each output visitor provide its own output collection function was the only remaining reason for exposing visitor sub-types to the rest of the code base. Add a polymorphic visit_complete() function which is a no-op for input visitors, and which populates an opaque pointer for output visitors. For maximum type-safety, also add a parameter to the output visitor constructors with a type-correct version of the output pointer, and assert that the two uses match. This approach was considered superior to either passing the output parameter only during construction (action at a distance during visit_free() feels awkward) or only during visit_complete() (defeating type safety makes it easier to use incorrectly). Most callers were function-local, and therefore a mechanical conversion; the testsuite was a bit trickier, but the previous cleanup patch minimized the churn here. The visit_complete() function may be called at most once; doing so lets us use transfer semantics rather than duplication or ref-count semantics to get the just-built output back to the caller, even though it means our behavior is not idempotent. Generated code is simplified as follows for events: |@@ -26,7 +26,7 @@ void qapi_event_send_acpi_device_ost(ACP | QDict *qmp; | Error *err = NULL; | QMPEventFuncEmit emit; |- QmpOutputVisitor *qov; |+ QObject *obj; | Visitor *v; | q_obj_ACPI_DEVICE_OST_arg param = { | info |@@ -39,8 +39,7 @@ void qapi_event_send_acpi_device_ost(ACP | | qmp = qmp_event_build_dict("ACPI_DEVICE_OST"); | |- qov = qmp_output_visitor_new(); |- v = qmp_output_get_visitor(qov); |+ v = qmp_output_visitor_new(&obj); | | visit_start_struct(v, "ACPI_DEVICE_OST", NULL, 0, &err); | if (err) { |@@ -55,7 +54,8 @@ void qapi_event_send_acpi_device_ost(ACP | goto out; | } | |- qdict_put_obj(qmp, "data", qmp_output_get_qobject(qov)); |+ visit_complete(v, &obj); |+ qdict_put_obj(qmp, "data", obj); | emit(QAPI_EVENT_ACPI_DEVICE_OST, qmp, &err); and for commands: | { | Error *err = NULL; |- QmpOutputVisitor *qov = qmp_output_visitor_new(); | Visitor *v; | |- v = qmp_output_get_visitor(qov); |+ v = qmp_output_visitor_new(ret_out); | visit_type_AddfdInfo(v, "unused", &ret_in, &err); |- if (err) { |- goto out; |+ if (!err) { |+ visit_complete(v, ret_out); | } |- *ret_out = qmp_output_get_qobject(qov); |- |-out: | error_propagate(errp, err); Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1465490926-28625-13-git-send-email-eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:43 +03:00
void visit_complete(Visitor *v, void *opaque)
{
assert(v->type != VISITOR_OUTPUT || v->complete);
trace_visit_complete(v, opaque);
qapi: Add new visit_complete() function Making each output visitor provide its own output collection function was the only remaining reason for exposing visitor sub-types to the rest of the code base. Add a polymorphic visit_complete() function which is a no-op for input visitors, and which populates an opaque pointer for output visitors. For maximum type-safety, also add a parameter to the output visitor constructors with a type-correct version of the output pointer, and assert that the two uses match. This approach was considered superior to either passing the output parameter only during construction (action at a distance during visit_free() feels awkward) or only during visit_complete() (defeating type safety makes it easier to use incorrectly). Most callers were function-local, and therefore a mechanical conversion; the testsuite was a bit trickier, but the previous cleanup patch minimized the churn here. The visit_complete() function may be called at most once; doing so lets us use transfer semantics rather than duplication or ref-count semantics to get the just-built output back to the caller, even though it means our behavior is not idempotent. Generated code is simplified as follows for events: |@@ -26,7 +26,7 @@ void qapi_event_send_acpi_device_ost(ACP | QDict *qmp; | Error *err = NULL; | QMPEventFuncEmit emit; |- QmpOutputVisitor *qov; |+ QObject *obj; | Visitor *v; | q_obj_ACPI_DEVICE_OST_arg param = { | info |@@ -39,8 +39,7 @@ void qapi_event_send_acpi_device_ost(ACP | | qmp = qmp_event_build_dict("ACPI_DEVICE_OST"); | |- qov = qmp_output_visitor_new(); |- v = qmp_output_get_visitor(qov); |+ v = qmp_output_visitor_new(&obj); | | visit_start_struct(v, "ACPI_DEVICE_OST", NULL, 0, &err); | if (err) { |@@ -55,7 +54,8 @@ void qapi_event_send_acpi_device_ost(ACP | goto out; | } | |- qdict_put_obj(qmp, "data", qmp_output_get_qobject(qov)); |+ visit_complete(v, &obj); |+ qdict_put_obj(qmp, "data", obj); | emit(QAPI_EVENT_ACPI_DEVICE_OST, qmp, &err); and for commands: | { | Error *err = NULL; |- QmpOutputVisitor *qov = qmp_output_visitor_new(); | Visitor *v; | |- v = qmp_output_get_visitor(qov); |+ v = qmp_output_visitor_new(ret_out); | visit_type_AddfdInfo(v, "unused", &ret_in, &err); |- if (err) { |- goto out; |+ if (!err) { |+ visit_complete(v, ret_out); | } |- *ret_out = qmp_output_get_qobject(qov); |- |-out: | error_propagate(errp, err); Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1465490926-28625-13-git-send-email-eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:43 +03:00
if (v->complete) {
v->complete(v, opaque);
}
}
void visit_free(Visitor *v)
{
trace_visit_free(v);
if (v) {
v->free(v);
}
}
bool visit_start_struct(Visitor *v, const char *name, void **obj,
size_t size, Error **errp)
{
bool ok;
trace_visit_start_struct(v, name, obj, size);
if (obj) {
assert(size);
qapi: Add new clone visitor We have a couple places in the code base that want to deep-clone one QAPI object into another, and they were resorting to serializing the struct out to QObject then reparsing it. A much more efficient version can be done by adding a new clone visitor. Since cloning is still relatively uncommon, expose the use of the new visitor via a QAPI_CLONE() macro that takes care of type-punning the underlying function pointer, rather than generating lots of unused functions for types that won't be cloned. And yes, we're relying on the compiler treating all pointers equally, even though a strict C program cannot portably do so - but we're not the first one in the qemu code base to expect it to work (hello, glib!). The choice of adding a fourth visitor type deserves some explanation. On the surface, the clone visitor is mostly an input visitor (it takes arbitrary input - in this case, another QAPI object - and creates a new QAPI object during the course of the visit). But ever since commit da72ab0 consolidated enum visits based on the visitor type, using VISITOR_INPUT would cause us to run visit_type_str(), even though for cloning there is nothing to do (we just copy the enum value across, without regards to its mapping to strings). Also, since our input happens to be a QAPI object, we can also satisfy the internal checks for VISITOR_OUTPUT. So in the end, I settled with a new VISITOR_CLONE, and chose its value such that many internal checks can use 'v->type & mask', sticking to 'v->type == value' where the difference matters. Note that we can only clone objects (including alternates) and lists, not built-ins or enums. The visitor core hides integer width from the actual visitor (since commit 04e070d), and as long as that's the case, we can't clone top-level integers. Then again, those can always be cloned by direct copy, since they are not objects with deep pointers, so it's no real loss. And restricting cloning to just objects and lists is cleaner than restricting it to non-integers. As such, I documented that the clone visitor is for direct use only by code internal to QAPI, and should not be used on incomplete objects (other than a hack to work around the fact that we allow NULL in place of "" in visit_type_str() in other output visitors). Note that as written, the clone visitor will never fail on a complete object. Scalars (including enums) not at the root of the clone copy just fine with no additional effort while visiting the scalar, by virtue of a g_memdup() each time we push another struct onto the stack. Cloning a string requires deduplication of a pointer, which means it can also provide the guarantee of an input visitor of never producing NULL even when still accepting NULL in place of "" the way the QMP output visitor does. Cloning an 'any' type could be possible by incrementing the QObject refcnt, but it's not obvious whether that is better than implementing a QObject deep clone. So for now, we document it as unsupported, and intentionally omit the .type_any() callback to let a developer know their usage needs implementation. Add testsuite coverage for several different clone situations, to ensure that the code is working. I also tested that valgrind was happy with the test. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1465490926-28625-14-git-send-email-eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:44 +03:00
assert(!(v->type & VISITOR_OUTPUT) || *obj);
}
ok = v->start_struct(v, name, obj, size, errp);
qapi: Add new clone visitor We have a couple places in the code base that want to deep-clone one QAPI object into another, and they were resorting to serializing the struct out to QObject then reparsing it. A much more efficient version can be done by adding a new clone visitor. Since cloning is still relatively uncommon, expose the use of the new visitor via a QAPI_CLONE() macro that takes care of type-punning the underlying function pointer, rather than generating lots of unused functions for types that won't be cloned. And yes, we're relying on the compiler treating all pointers equally, even though a strict C program cannot portably do so - but we're not the first one in the qemu code base to expect it to work (hello, glib!). The choice of adding a fourth visitor type deserves some explanation. On the surface, the clone visitor is mostly an input visitor (it takes arbitrary input - in this case, another QAPI object - and creates a new QAPI object during the course of the visit). But ever since commit da72ab0 consolidated enum visits based on the visitor type, using VISITOR_INPUT would cause us to run visit_type_str(), even though for cloning there is nothing to do (we just copy the enum value across, without regards to its mapping to strings). Also, since our input happens to be a QAPI object, we can also satisfy the internal checks for VISITOR_OUTPUT. So in the end, I settled with a new VISITOR_CLONE, and chose its value such that many internal checks can use 'v->type & mask', sticking to 'v->type == value' where the difference matters. Note that we can only clone objects (including alternates) and lists, not built-ins or enums. The visitor core hides integer width from the actual visitor (since commit 04e070d), and as long as that's the case, we can't clone top-level integers. Then again, those can always be cloned by direct copy, since they are not objects with deep pointers, so it's no real loss. And restricting cloning to just objects and lists is cleaner than restricting it to non-integers. As such, I documented that the clone visitor is for direct use only by code internal to QAPI, and should not be used on incomplete objects (other than a hack to work around the fact that we allow NULL in place of "" in visit_type_str() in other output visitors). Note that as written, the clone visitor will never fail on a complete object. Scalars (including enums) not at the root of the clone copy just fine with no additional effort while visiting the scalar, by virtue of a g_memdup() each time we push another struct onto the stack. Cloning a string requires deduplication of a pointer, which means it can also provide the guarantee of an input visitor of never producing NULL even when still accepting NULL in place of "" the way the QMP output visitor does. Cloning an 'any' type could be possible by incrementing the QObject refcnt, but it's not obvious whether that is better than implementing a QObject deep clone. So for now, we document it as unsupported, and intentionally omit the .type_any() callback to let a developer know their usage needs implementation. Add testsuite coverage for several different clone situations, to ensure that the code is working. I also tested that valgrind was happy with the test. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1465490926-28625-14-git-send-email-eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:44 +03:00
if (obj && (v->type & VISITOR_INPUT)) {
assert(ok != !*obj);
}
return ok;
}
bool visit_check_struct(Visitor *v, Error **errp)
{
trace_visit_check_struct(v);
return v->check_struct ? v->check_struct(v, errp) : true;
qapi: Split visit_end_struct() into pieces As mentioned in previous patches, we want to call visit_end_struct() functions unconditionally, so that visitors can release resources tied up since the matching visit_start_struct() without also having to worry about error priority if more than one error occurs. Even though error_propagate() can be safely used to ignore a second error during cleanup caused by a first error, it is simpler if the cleanup cannot set an error. So, split out the error checking portion (basically, input visitors checking for unvisited keys) into a new function visit_check_struct(), which can be safely skipped if any earlier errors are encountered, and leave the cleanup portion (which never fails, but must be called unconditionally if visit_start_struct() succeeded) in visit_end_struct(). Generated code in qapi-visit.c has diffs resembling: |@@ -59,10 +59,12 @@ void visit_type_ACPIOSTInfo(Visitor *v, | goto out_obj; | } | visit_type_ACPIOSTInfo_members(v, obj, &err); |- error_propagate(errp, err); |- err = NULL; |+ if (err) { |+ goto out_obj; |+ } |+ visit_check_struct(v, &err); | out_obj: |- visit_end_struct(v, &err); |+ visit_end_struct(v); | out: and in qapi-event.c: @@ -47,7 +47,10 @@ void qapi_event_send_acpi_device_ost(ACP | goto out; | } | visit_type_q_obj_ACPI_DEVICE_OST_arg_members(v, &param, &err); |- visit_end_struct(v, err ? NULL : &err); |+ if (!err) { |+ visit_check_struct(v, &err); |+ } |+ visit_end_struct(v); | if (err) { | goto out; Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1461879932-9020-20-git-send-email-eblake@redhat.com> [Conflict with a doc fixup resolved] Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-04-29 00:45:27 +03:00
}
2016-06-09 19:48:34 +03:00
void visit_end_struct(Visitor *v, void **obj)
qapi: Split visit_end_struct() into pieces As mentioned in previous patches, we want to call visit_end_struct() functions unconditionally, so that visitors can release resources tied up since the matching visit_start_struct() without also having to worry about error priority if more than one error occurs. Even though error_propagate() can be safely used to ignore a second error during cleanup caused by a first error, it is simpler if the cleanup cannot set an error. So, split out the error checking portion (basically, input visitors checking for unvisited keys) into a new function visit_check_struct(), which can be safely skipped if any earlier errors are encountered, and leave the cleanup portion (which never fails, but must be called unconditionally if visit_start_struct() succeeded) in visit_end_struct(). Generated code in qapi-visit.c has diffs resembling: |@@ -59,10 +59,12 @@ void visit_type_ACPIOSTInfo(Visitor *v, | goto out_obj; | } | visit_type_ACPIOSTInfo_members(v, obj, &err); |- error_propagate(errp, err); |- err = NULL; |+ if (err) { |+ goto out_obj; |+ } |+ visit_check_struct(v, &err); | out_obj: |- visit_end_struct(v, &err); |+ visit_end_struct(v); | out: and in qapi-event.c: @@ -47,7 +47,10 @@ void qapi_event_send_acpi_device_ost(ACP | goto out; | } | visit_type_q_obj_ACPI_DEVICE_OST_arg_members(v, &param, &err); |- visit_end_struct(v, err ? NULL : &err); |+ if (!err) { |+ visit_check_struct(v, &err); |+ } |+ visit_end_struct(v); | if (err) { | goto out; Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1461879932-9020-20-git-send-email-eblake@redhat.com> [Conflict with a doc fixup resolved] Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-04-29 00:45:27 +03:00
{
trace_visit_end_struct(v, obj);
2016-06-09 19:48:34 +03:00
v->end_struct(v, obj);
}
bool visit_start_list(Visitor *v, const char *name, GenericList **list,
qapi: Simplify semantics of visit_next_list() The semantics of the list visit are somewhat baroque, with the following pseudocode when FooList is used: start() for (prev = head; cur = next(prev); prev = &cur) { visit(&cur->value) } Note that these semantics (advance before visit) requires that the first call to next() return the list head, while all other calls return the next element of the list; that is, every visitor implementation is required to track extra state to decide whether to return the input as-is, or to advance. It also requires an argument of 'GenericList **' to next(), solely because the first iteration might need to modify the caller's GenericList head, so that all other calls have to do a layer of dereferencing. Thankfully, we only have two uses of list visits in the entire code base: one in spapr_drc (which completely avoids visit_next_list(), feeding in integers from a different source than uint8List), and one in qapi-visit.py. That is, all other list visitors are generated in qapi-visit.c, and share the same paradigm based on a qapi FooList type, so we can refactor how lists are laid out with minimal churn among clients. We can greatly simplify things by hoisting the special case into the start() routine, and flipping the order in the loop to visit before advance: start(head) for (tail = *head; tail; tail = next(tail)) { visit(&tail->value) } With the simpler semantics, visitors have less state to track, the argument to next() is reduced to 'GenericList *', and it also becomes obvious whether an input visitor is allocating a FooList during visit_start_list() (rather than the old way of not knowing if an allocation happened until the first visit_next_list()). As a minor drawback, we now allocate in two functions instead of one, and have to pass the size to both functions (unless we were to tweak the input visitors to cache the size to start_list for reuse during next_list, but that defeats the goal of less visitor state). The signature of visit_start_list() is chosen to match visit_start_struct(), with the new parameters after 'name'. The spapr_drc case is a virtual visit, done by passing NULL for list, similarly to how NULL is passed to visit_start_struct() when a qapi type is not used in those visits. It was easy to provide these semantics for qmp-output and dealloc visitors, and a bit harder for qmp-input (several prerequisite patches refactored things to make this patch straightforward). But it turned out that the string and opts visitors munge enough other state during visit_next_list() to make it easier to just document and require a GenericList visit for now; an assertion will remind us to adjust things if we need the semantics in the future. Several pre-requisite cleanup patches made the reshuffling of the various visitors easier; particularly the qmp input visitor. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1461879932-9020-24-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-04-29 00:45:31 +03:00
size_t size, Error **errp)
{
bool ok;
qapi: Simplify semantics of visit_next_list() The semantics of the list visit are somewhat baroque, with the following pseudocode when FooList is used: start() for (prev = head; cur = next(prev); prev = &cur) { visit(&cur->value) } Note that these semantics (advance before visit) requires that the first call to next() return the list head, while all other calls return the next element of the list; that is, every visitor implementation is required to track extra state to decide whether to return the input as-is, or to advance. It also requires an argument of 'GenericList **' to next(), solely because the first iteration might need to modify the caller's GenericList head, so that all other calls have to do a layer of dereferencing. Thankfully, we only have two uses of list visits in the entire code base: one in spapr_drc (which completely avoids visit_next_list(), feeding in integers from a different source than uint8List), and one in qapi-visit.py. That is, all other list visitors are generated in qapi-visit.c, and share the same paradigm based on a qapi FooList type, so we can refactor how lists are laid out with minimal churn among clients. We can greatly simplify things by hoisting the special case into the start() routine, and flipping the order in the loop to visit before advance: start(head) for (tail = *head; tail; tail = next(tail)) { visit(&tail->value) } With the simpler semantics, visitors have less state to track, the argument to next() is reduced to 'GenericList *', and it also becomes obvious whether an input visitor is allocating a FooList during visit_start_list() (rather than the old way of not knowing if an allocation happened until the first visit_next_list()). As a minor drawback, we now allocate in two functions instead of one, and have to pass the size to both functions (unless we were to tweak the input visitors to cache the size to start_list for reuse during next_list, but that defeats the goal of less visitor state). The signature of visit_start_list() is chosen to match visit_start_struct(), with the new parameters after 'name'. The spapr_drc case is a virtual visit, done by passing NULL for list, similarly to how NULL is passed to visit_start_struct() when a qapi type is not used in those visits. It was easy to provide these semantics for qmp-output and dealloc visitors, and a bit harder for qmp-input (several prerequisite patches refactored things to make this patch straightforward). But it turned out that the string and opts visitors munge enough other state during visit_next_list() to make it easier to just document and require a GenericList visit for now; an assertion will remind us to adjust things if we need the semantics in the future. Several pre-requisite cleanup patches made the reshuffling of the various visitors easier; particularly the qmp input visitor. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1461879932-9020-24-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-04-29 00:45:31 +03:00
assert(!list || size >= sizeof(GenericList));
trace_visit_start_list(v, name, list, size);
ok = v->start_list(v, name, list, size, errp);
qapi: Add new clone visitor We have a couple places in the code base that want to deep-clone one QAPI object into another, and they were resorting to serializing the struct out to QObject then reparsing it. A much more efficient version can be done by adding a new clone visitor. Since cloning is still relatively uncommon, expose the use of the new visitor via a QAPI_CLONE() macro that takes care of type-punning the underlying function pointer, rather than generating lots of unused functions for types that won't be cloned. And yes, we're relying on the compiler treating all pointers equally, even though a strict C program cannot portably do so - but we're not the first one in the qemu code base to expect it to work (hello, glib!). The choice of adding a fourth visitor type deserves some explanation. On the surface, the clone visitor is mostly an input visitor (it takes arbitrary input - in this case, another QAPI object - and creates a new QAPI object during the course of the visit). But ever since commit da72ab0 consolidated enum visits based on the visitor type, using VISITOR_INPUT would cause us to run visit_type_str(), even though for cloning there is nothing to do (we just copy the enum value across, without regards to its mapping to strings). Also, since our input happens to be a QAPI object, we can also satisfy the internal checks for VISITOR_OUTPUT. So in the end, I settled with a new VISITOR_CLONE, and chose its value such that many internal checks can use 'v->type & mask', sticking to 'v->type == value' where the difference matters. Note that we can only clone objects (including alternates) and lists, not built-ins or enums. The visitor core hides integer width from the actual visitor (since commit 04e070d), and as long as that's the case, we can't clone top-level integers. Then again, those can always be cloned by direct copy, since they are not objects with deep pointers, so it's no real loss. And restricting cloning to just objects and lists is cleaner than restricting it to non-integers. As such, I documented that the clone visitor is for direct use only by code internal to QAPI, and should not be used on incomplete objects (other than a hack to work around the fact that we allow NULL in place of "" in visit_type_str() in other output visitors). Note that as written, the clone visitor will never fail on a complete object. Scalars (including enums) not at the root of the clone copy just fine with no additional effort while visiting the scalar, by virtue of a g_memdup() each time we push another struct onto the stack. Cloning a string requires deduplication of a pointer, which means it can also provide the guarantee of an input visitor of never producing NULL even when still accepting NULL in place of "" the way the QMP output visitor does. Cloning an 'any' type could be possible by incrementing the QObject refcnt, but it's not obvious whether that is better than implementing a QObject deep clone. So for now, we document it as unsupported, and intentionally omit the .type_any() callback to let a developer know their usage needs implementation. Add testsuite coverage for several different clone situations, to ensure that the code is working. I also tested that valgrind was happy with the test. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1465490926-28625-14-git-send-email-eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:44 +03:00
if (list && (v->type & VISITOR_INPUT)) {
assert(ok || !*list);
qapi: Simplify semantics of visit_next_list() The semantics of the list visit are somewhat baroque, with the following pseudocode when FooList is used: start() for (prev = head; cur = next(prev); prev = &cur) { visit(&cur->value) } Note that these semantics (advance before visit) requires that the first call to next() return the list head, while all other calls return the next element of the list; that is, every visitor implementation is required to track extra state to decide whether to return the input as-is, or to advance. It also requires an argument of 'GenericList **' to next(), solely because the first iteration might need to modify the caller's GenericList head, so that all other calls have to do a layer of dereferencing. Thankfully, we only have two uses of list visits in the entire code base: one in spapr_drc (which completely avoids visit_next_list(), feeding in integers from a different source than uint8List), and one in qapi-visit.py. That is, all other list visitors are generated in qapi-visit.c, and share the same paradigm based on a qapi FooList type, so we can refactor how lists are laid out with minimal churn among clients. We can greatly simplify things by hoisting the special case into the start() routine, and flipping the order in the loop to visit before advance: start(head) for (tail = *head; tail; tail = next(tail)) { visit(&tail->value) } With the simpler semantics, visitors have less state to track, the argument to next() is reduced to 'GenericList *', and it also becomes obvious whether an input visitor is allocating a FooList during visit_start_list() (rather than the old way of not knowing if an allocation happened until the first visit_next_list()). As a minor drawback, we now allocate in two functions instead of one, and have to pass the size to both functions (unless we were to tweak the input visitors to cache the size to start_list for reuse during next_list, but that defeats the goal of less visitor state). The signature of visit_start_list() is chosen to match visit_start_struct(), with the new parameters after 'name'. The spapr_drc case is a virtual visit, done by passing NULL for list, similarly to how NULL is passed to visit_start_struct() when a qapi type is not used in those visits. It was easy to provide these semantics for qmp-output and dealloc visitors, and a bit harder for qmp-input (several prerequisite patches refactored things to make this patch straightforward). But it turned out that the string and opts visitors munge enough other state during visit_next_list() to make it easier to just document and require a GenericList visit for now; an assertion will remind us to adjust things if we need the semantics in the future. Several pre-requisite cleanup patches made the reshuffling of the various visitors easier; particularly the qmp input visitor. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1461879932-9020-24-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-04-29 00:45:31 +03:00
}
return ok;
}
qapi: Simplify semantics of visit_next_list() The semantics of the list visit are somewhat baroque, with the following pseudocode when FooList is used: start() for (prev = head; cur = next(prev); prev = &cur) { visit(&cur->value) } Note that these semantics (advance before visit) requires that the first call to next() return the list head, while all other calls return the next element of the list; that is, every visitor implementation is required to track extra state to decide whether to return the input as-is, or to advance. It also requires an argument of 'GenericList **' to next(), solely because the first iteration might need to modify the caller's GenericList head, so that all other calls have to do a layer of dereferencing. Thankfully, we only have two uses of list visits in the entire code base: one in spapr_drc (which completely avoids visit_next_list(), feeding in integers from a different source than uint8List), and one in qapi-visit.py. That is, all other list visitors are generated in qapi-visit.c, and share the same paradigm based on a qapi FooList type, so we can refactor how lists are laid out with minimal churn among clients. We can greatly simplify things by hoisting the special case into the start() routine, and flipping the order in the loop to visit before advance: start(head) for (tail = *head; tail; tail = next(tail)) { visit(&tail->value) } With the simpler semantics, visitors have less state to track, the argument to next() is reduced to 'GenericList *', and it also becomes obvious whether an input visitor is allocating a FooList during visit_start_list() (rather than the old way of not knowing if an allocation happened until the first visit_next_list()). As a minor drawback, we now allocate in two functions instead of one, and have to pass the size to both functions (unless we were to tweak the input visitors to cache the size to start_list for reuse during next_list, but that defeats the goal of less visitor state). The signature of visit_start_list() is chosen to match visit_start_struct(), with the new parameters after 'name'. The spapr_drc case is a virtual visit, done by passing NULL for list, similarly to how NULL is passed to visit_start_struct() when a qapi type is not used in those visits. It was easy to provide these semantics for qmp-output and dealloc visitors, and a bit harder for qmp-input (several prerequisite patches refactored things to make this patch straightforward). But it turned out that the string and opts visitors munge enough other state during visit_next_list() to make it easier to just document and require a GenericList visit for now; an assertion will remind us to adjust things if we need the semantics in the future. Several pre-requisite cleanup patches made the reshuffling of the various visitors easier; particularly the qmp input visitor. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1461879932-9020-24-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-04-29 00:45:31 +03:00
GenericList *visit_next_list(Visitor *v, GenericList *tail, size_t size)
{
qapi: Simplify semantics of visit_next_list() The semantics of the list visit are somewhat baroque, with the following pseudocode when FooList is used: start() for (prev = head; cur = next(prev); prev = &cur) { visit(&cur->value) } Note that these semantics (advance before visit) requires that the first call to next() return the list head, while all other calls return the next element of the list; that is, every visitor implementation is required to track extra state to decide whether to return the input as-is, or to advance. It also requires an argument of 'GenericList **' to next(), solely because the first iteration might need to modify the caller's GenericList head, so that all other calls have to do a layer of dereferencing. Thankfully, we only have two uses of list visits in the entire code base: one in spapr_drc (which completely avoids visit_next_list(), feeding in integers from a different source than uint8List), and one in qapi-visit.py. That is, all other list visitors are generated in qapi-visit.c, and share the same paradigm based on a qapi FooList type, so we can refactor how lists are laid out with minimal churn among clients. We can greatly simplify things by hoisting the special case into the start() routine, and flipping the order in the loop to visit before advance: start(head) for (tail = *head; tail; tail = next(tail)) { visit(&tail->value) } With the simpler semantics, visitors have less state to track, the argument to next() is reduced to 'GenericList *', and it also becomes obvious whether an input visitor is allocating a FooList during visit_start_list() (rather than the old way of not knowing if an allocation happened until the first visit_next_list()). As a minor drawback, we now allocate in two functions instead of one, and have to pass the size to both functions (unless we were to tweak the input visitors to cache the size to start_list for reuse during next_list, but that defeats the goal of less visitor state). The signature of visit_start_list() is chosen to match visit_start_struct(), with the new parameters after 'name'. The spapr_drc case is a virtual visit, done by passing NULL for list, similarly to how NULL is passed to visit_start_struct() when a qapi type is not used in those visits. It was easy to provide these semantics for qmp-output and dealloc visitors, and a bit harder for qmp-input (several prerequisite patches refactored things to make this patch straightforward). But it turned out that the string and opts visitors munge enough other state during visit_next_list() to make it easier to just document and require a GenericList visit for now; an assertion will remind us to adjust things if we need the semantics in the future. Several pre-requisite cleanup patches made the reshuffling of the various visitors easier; particularly the qmp input visitor. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1461879932-9020-24-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-04-29 00:45:31 +03:00
assert(tail && size >= sizeof(GenericList));
trace_visit_next_list(v, tail, size);
qapi: Simplify semantics of visit_next_list() The semantics of the list visit are somewhat baroque, with the following pseudocode when FooList is used: start() for (prev = head; cur = next(prev); prev = &cur) { visit(&cur->value) } Note that these semantics (advance before visit) requires that the first call to next() return the list head, while all other calls return the next element of the list; that is, every visitor implementation is required to track extra state to decide whether to return the input as-is, or to advance. It also requires an argument of 'GenericList **' to next(), solely because the first iteration might need to modify the caller's GenericList head, so that all other calls have to do a layer of dereferencing. Thankfully, we only have two uses of list visits in the entire code base: one in spapr_drc (which completely avoids visit_next_list(), feeding in integers from a different source than uint8List), and one in qapi-visit.py. That is, all other list visitors are generated in qapi-visit.c, and share the same paradigm based on a qapi FooList type, so we can refactor how lists are laid out with minimal churn among clients. We can greatly simplify things by hoisting the special case into the start() routine, and flipping the order in the loop to visit before advance: start(head) for (tail = *head; tail; tail = next(tail)) { visit(&tail->value) } With the simpler semantics, visitors have less state to track, the argument to next() is reduced to 'GenericList *', and it also becomes obvious whether an input visitor is allocating a FooList during visit_start_list() (rather than the old way of not knowing if an allocation happened until the first visit_next_list()). As a minor drawback, we now allocate in two functions instead of one, and have to pass the size to both functions (unless we were to tweak the input visitors to cache the size to start_list for reuse during next_list, but that defeats the goal of less visitor state). The signature of visit_start_list() is chosen to match visit_start_struct(), with the new parameters after 'name'. The spapr_drc case is a virtual visit, done by passing NULL for list, similarly to how NULL is passed to visit_start_struct() when a qapi type is not used in those visits. It was easy to provide these semantics for qmp-output and dealloc visitors, and a bit harder for qmp-input (several prerequisite patches refactored things to make this patch straightforward). But it turned out that the string and opts visitors munge enough other state during visit_next_list() to make it easier to just document and require a GenericList visit for now; an assertion will remind us to adjust things if we need the semantics in the future. Several pre-requisite cleanup patches made the reshuffling of the various visitors easier; particularly the qmp input visitor. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1461879932-9020-24-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-04-29 00:45:31 +03:00
return v->next_list(v, tail, size);
}
bool visit_check_list(Visitor *v, Error **errp)
{
trace_visit_check_list(v);
return v->check_list ? v->check_list(v, errp) : true;
}
2016-06-09 19:48:34 +03:00
void visit_end_list(Visitor *v, void **obj)
{
trace_visit_end_list(v, obj);
2016-06-09 19:48:34 +03:00
v->end_list(v, obj);
}
bool visit_start_alternate(Visitor *v, const char *name,
GenericAlternate **obj, size_t size,
Error **errp)
{
bool ok;
assert(obj && size >= sizeof(GenericAlternate));
qapi: Add new clone visitor We have a couple places in the code base that want to deep-clone one QAPI object into another, and they were resorting to serializing the struct out to QObject then reparsing it. A much more efficient version can be done by adding a new clone visitor. Since cloning is still relatively uncommon, expose the use of the new visitor via a QAPI_CLONE() macro that takes care of type-punning the underlying function pointer, rather than generating lots of unused functions for types that won't be cloned. And yes, we're relying on the compiler treating all pointers equally, even though a strict C program cannot portably do so - but we're not the first one in the qemu code base to expect it to work (hello, glib!). The choice of adding a fourth visitor type deserves some explanation. On the surface, the clone visitor is mostly an input visitor (it takes arbitrary input - in this case, another QAPI object - and creates a new QAPI object during the course of the visit). But ever since commit da72ab0 consolidated enum visits based on the visitor type, using VISITOR_INPUT would cause us to run visit_type_str(), even though for cloning there is nothing to do (we just copy the enum value across, without regards to its mapping to strings). Also, since our input happens to be a QAPI object, we can also satisfy the internal checks for VISITOR_OUTPUT. So in the end, I settled with a new VISITOR_CLONE, and chose its value such that many internal checks can use 'v->type & mask', sticking to 'v->type == value' where the difference matters. Note that we can only clone objects (including alternates) and lists, not built-ins or enums. The visitor core hides integer width from the actual visitor (since commit 04e070d), and as long as that's the case, we can't clone top-level integers. Then again, those can always be cloned by direct copy, since they are not objects with deep pointers, so it's no real loss. And restricting cloning to just objects and lists is cleaner than restricting it to non-integers. As such, I documented that the clone visitor is for direct use only by code internal to QAPI, and should not be used on incomplete objects (other than a hack to work around the fact that we allow NULL in place of "" in visit_type_str() in other output visitors). Note that as written, the clone visitor will never fail on a complete object. Scalars (including enums) not at the root of the clone copy just fine with no additional effort while visiting the scalar, by virtue of a g_memdup() each time we push another struct onto the stack. Cloning a string requires deduplication of a pointer, which means it can also provide the guarantee of an input visitor of never producing NULL even when still accepting NULL in place of "" the way the QMP output visitor does. Cloning an 'any' type could be possible by incrementing the QObject refcnt, but it's not obvious whether that is better than implementing a QObject deep clone. So for now, we document it as unsupported, and intentionally omit the .type_any() callback to let a developer know their usage needs implementation. Add testsuite coverage for several different clone situations, to ensure that the code is working. I also tested that valgrind was happy with the test. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1465490926-28625-14-git-send-email-eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:44 +03:00
assert(!(v->type & VISITOR_OUTPUT) || *obj);
trace_visit_start_alternate(v, name, obj, size);
if (!v->start_alternate) {
assert(!(v->type & VISITOR_INPUT));
return true;
}
ok = v->start_alternate(v, name, obj, size, errp);
qapi: Add new clone visitor We have a couple places in the code base that want to deep-clone one QAPI object into another, and they were resorting to serializing the struct out to QObject then reparsing it. A much more efficient version can be done by adding a new clone visitor. Since cloning is still relatively uncommon, expose the use of the new visitor via a QAPI_CLONE() macro that takes care of type-punning the underlying function pointer, rather than generating lots of unused functions for types that won't be cloned. And yes, we're relying on the compiler treating all pointers equally, even though a strict C program cannot portably do so - but we're not the first one in the qemu code base to expect it to work (hello, glib!). The choice of adding a fourth visitor type deserves some explanation. On the surface, the clone visitor is mostly an input visitor (it takes arbitrary input - in this case, another QAPI object - and creates a new QAPI object during the course of the visit). But ever since commit da72ab0 consolidated enum visits based on the visitor type, using VISITOR_INPUT would cause us to run visit_type_str(), even though for cloning there is nothing to do (we just copy the enum value across, without regards to its mapping to strings). Also, since our input happens to be a QAPI object, we can also satisfy the internal checks for VISITOR_OUTPUT. So in the end, I settled with a new VISITOR_CLONE, and chose its value such that many internal checks can use 'v->type & mask', sticking to 'v->type == value' where the difference matters. Note that we can only clone objects (including alternates) and lists, not built-ins or enums. The visitor core hides integer width from the actual visitor (since commit 04e070d), and as long as that's the case, we can't clone top-level integers. Then again, those can always be cloned by direct copy, since they are not objects with deep pointers, so it's no real loss. And restricting cloning to just objects and lists is cleaner than restricting it to non-integers. As such, I documented that the clone visitor is for direct use only by code internal to QAPI, and should not be used on incomplete objects (other than a hack to work around the fact that we allow NULL in place of "" in visit_type_str() in other output visitors). Note that as written, the clone visitor will never fail on a complete object. Scalars (including enums) not at the root of the clone copy just fine with no additional effort while visiting the scalar, by virtue of a g_memdup() each time we push another struct onto the stack. Cloning a string requires deduplication of a pointer, which means it can also provide the guarantee of an input visitor of never producing NULL even when still accepting NULL in place of "" the way the QMP output visitor does. Cloning an 'any' type could be possible by incrementing the QObject refcnt, but it's not obvious whether that is better than implementing a QObject deep clone. So for now, we document it as unsupported, and intentionally omit the .type_any() callback to let a developer know their usage needs implementation. Add testsuite coverage for several different clone situations, to ensure that the code is working. I also tested that valgrind was happy with the test. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1465490926-28625-14-git-send-email-eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:44 +03:00
if (v->type & VISITOR_INPUT) {
assert(ok != !*obj);
}
return ok;
}
2016-06-09 19:48:34 +03:00
void visit_end_alternate(Visitor *v, void **obj)
{
trace_visit_end_alternate(v, obj);
if (v->end_alternate) {
2016-06-09 19:48:34 +03:00
v->end_alternate(v, obj);
}
}
bool visit_optional(Visitor *v, const char *name, bool *present)
{
trace_visit_optional(v, name, present);
if (v->optional) {
v->optional(v, name, present);
}
return *present;
}
qapi: Change visit_type_FOO() to no longer return partial objects Returning a partial object on error is an invitation for a careless caller to leak memory. We already fixed things in an earlier patch to guarantee NULL if visit_start fails ("qapi: Guarantee NULL obj on input visitor callback error"), but that does not help the case where visit_start succeeds but some other failure happens before visit_end, such that we leak a partially constructed object outside visit_type_FOO(). As no one outside the testsuite was actually relying on these semantics, it is cleaner to just document and guarantee that ALL pointer-based visit_type_FOO() functions always leave a safe value in *obj during an input visitor (either the new object on success, or NULL if an error is encountered), so callers can now unconditionally use qapi_free_FOO() to clean up regardless of whether an error occurred. The decision is done by adding visit_is_input(), then updating the generated code to check if additional cleanup is needed based on the type of visitor in use. Note that we still leave *obj unchanged after a scalar-based visit_type_FOO(); I did not feel like auditing all uses of visit_type_Enum() to see if the callers would tolerate a specific sentinel value (not to mention having to decide whether it would be better to use 0 or ENUM__MAX as that sentinel). Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1461879932-9020-25-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-04-29 00:45:32 +03:00
bool visit_is_input(Visitor *v)
{
return v->type == VISITOR_INPUT;
}
bool visit_is_dealloc(Visitor *v)
{
return v->type == VISITOR_DEALLOC;
}
bool visit_type_int(Visitor *v, const char *name, int64_t *obj, Error **errp)
{
assert(obj);
trace_visit_type_int(v, name, obj);
return v->type_int64(v, name, obj, errp);
}
static bool visit_type_uintN(Visitor *v, uint64_t *obj, const char *name,
uint64_t max, const char *type, Error **errp)
{
uint64_t value = *obj;
assert(v->type == VISITOR_INPUT || value <= max);
if (!v->type_uint64(v, name, &value, errp)) {
return false;
}
if (value > max) {
assert(v->type == VISITOR_INPUT);
error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
name ? name : "null", type);
return false;
}
*obj = value;
return true;
}
bool visit_type_uint8(Visitor *v, const char *name, uint8_t *obj,
qapi: Swap visit_* arguments for consistent 'name' placement JSON uses "name":value, but many of our visitor interfaces were called with visit_type_FOO(v, &value, name, errp). This can be a bit confusing to have to mentally swap the parameter order to match JSON order. It's particularly bad for visit_start_struct(), where the 'name' parameter is smack in the middle of the otherwise-related group of 'obj, kind, size' parameters! It's time to do a global swap of the parameter ordering, so that the 'name' parameter is always immediately after the Visitor argument. Additional reason in favor of the swap: the existing include/qjson.h prefers listing 'name' first in json_prop_*(), and I have plans to unify that file with the qapi visitors; listing 'name' first in qapi will minimize churn to the (admittedly few) qjson.h clients. Later patches will then fix docs, object.h, visitor-impl.h, and those clients to match. Done by first patching scripts/qapi*.py by hand to make generated files do what I want, then by running the following Coccinelle script to affect the rest of the code base: $ spatch --sp-file script `git grep -l '\bvisit_' -- '**/*.[ch]'` I then had to apply some touchups (Coccinelle insisted on TAB indentation in visitor.h, and botched the signature of visit_type_enum() by rewriting 'const char *const strings[]' to the syntactically invalid 'const char*const[] strings'). The movement of parameters is sufficient to provoke compiler errors if any callers were missed. // Part 1: Swap declaration order @@ type TV, TErr, TObj, T1, T2; identifier OBJ, ARG1, ARG2; @@ void visit_start_struct -(TV v, TObj OBJ, T1 ARG1, const char *name, T2 ARG2, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, T2 ARG2, TErr errp) { ... } @@ type bool, TV, T1; identifier ARG1; @@ bool visit_optional -(TV v, T1 ARG1, const char *name) +(TV v, const char *name, T1 ARG1) { ... } @@ type TV, TErr, TObj, T1; identifier OBJ, ARG1; @@ void visit_get_next_type -(TV v, TObj OBJ, T1 ARG1, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, TErr errp) { ... } @@ type TV, TErr, TObj, T1, T2; identifier OBJ, ARG1, ARG2; @@ void visit_type_enum -(TV v, TObj OBJ, T1 ARG1, T2 ARG2, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, T2 ARG2, TErr errp) { ... } @@ type TV, TErr, TObj; identifier OBJ; identifier VISIT_TYPE =~ "^visit_type_"; @@ void VISIT_TYPE -(TV v, TObj OBJ, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, TErr errp) { ... } // Part 2: swap caller order @@ expression V, NAME, OBJ, ARG1, ARG2, ERR; identifier VISIT_TYPE =~ "^visit_type_"; @@ ( -visit_start_struct(V, OBJ, ARG1, NAME, ARG2, ERR) +visit_start_struct(V, NAME, OBJ, ARG1, ARG2, ERR) | -visit_optional(V, ARG1, NAME) +visit_optional(V, NAME, ARG1) | -visit_get_next_type(V, OBJ, ARG1, NAME, ERR) +visit_get_next_type(V, NAME, OBJ, ARG1, ERR) | -visit_type_enum(V, OBJ, ARG1, ARG2, NAME, ERR) +visit_type_enum(V, NAME, OBJ, ARG1, ARG2, ERR) | -VISIT_TYPE(V, OBJ, NAME, ERR) +VISIT_TYPE(V, NAME, OBJ, ERR) ) Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-Id: <1454075341-13658-19-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-01-29 16:48:54 +03:00
Error **errp)
{
uint64_t value;
bool ok;
trace_visit_type_uint8(v, name, obj);
value = *obj;
ok = visit_type_uintN(v, &value, name, UINT8_MAX, "uint8_t", errp);
*obj = value;
return ok;
}
bool visit_type_uint16(Visitor *v, const char *name, uint16_t *obj,
Error **errp)
{
uint64_t value;
bool ok;
trace_visit_type_uint16(v, name, obj);
value = *obj;
ok = visit_type_uintN(v, &value, name, UINT16_MAX, "uint16_t", errp);
*obj = value;
return ok;
}
qapi: Replace uncommon use of the error API by the common one We commonly use the error API like this: err = NULL; foo(..., &err); if (err) { goto out; } bar(..., &err); Every error source is checked separately. The second function is only called when the first one succeeds. Both functions are free to pass their argument to error_set(). Because error_set() asserts no error has been set, this effectively means they must not be called with an error set. The qapi-generated code uses the error API differently: // *errp was initialized to NULL somewhere up the call chain frob(..., errp); gnat(..., errp); Errors accumulate in *errp: first error wins, subsequent errors get dropped. To make this work, the second function does nothing when called with an error set. Requires non-null errp, or else the second function can't see the first one fail. This usage has also bled into visitor tests, and two device model object property getters rtc_get_date() and balloon_stats_get_all(). With the "accumulate" technique, you need fewer error checks in callers, and buy that with an error check in every callee. Can be nice. However, mixing the two techniques is confusing. You can't use the "accumulate" technique with functions designed for the "check separately" technique. You can use the "check separately" technique with functions designed for the "accumulate" technique, but then error_set() can't catch you setting an error more than once. Standardize on the "check separately" technique for now, because it's overwhelmingly prevalent. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
2014-05-07 11:53:54 +04:00
bool visit_type_uint32(Visitor *v, const char *name, uint32_t *obj,
Error **errp)
{
uint64_t value;
bool ok;
trace_visit_type_uint32(v, name, obj);
value = *obj;
ok = visit_type_uintN(v, &value, name, UINT32_MAX, "uint32_t", errp);
*obj = value;
return ok;
}
bool visit_type_uint64(Visitor *v, const char *name, uint64_t *obj,
Error **errp)
{
assert(obj);
trace_visit_type_uint64(v, name, obj);
return v->type_uint64(v, name, obj, errp);
}
static bool visit_type_intN(Visitor *v, int64_t *obj, const char *name,
int64_t min, int64_t max, const char *type,
Error **errp)
{
int64_t value = *obj;
qapi: Replace uncommon use of the error API by the common one We commonly use the error API like this: err = NULL; foo(..., &err); if (err) { goto out; } bar(..., &err); Every error source is checked separately. The second function is only called when the first one succeeds. Both functions are free to pass their argument to error_set(). Because error_set() asserts no error has been set, this effectively means they must not be called with an error set. The qapi-generated code uses the error API differently: // *errp was initialized to NULL somewhere up the call chain frob(..., errp); gnat(..., errp); Errors accumulate in *errp: first error wins, subsequent errors get dropped. To make this work, the second function does nothing when called with an error set. Requires non-null errp, or else the second function can't see the first one fail. This usage has also bled into visitor tests, and two device model object property getters rtc_get_date() and balloon_stats_get_all(). With the "accumulate" technique, you need fewer error checks in callers, and buy that with an error check in every callee. Can be nice. However, mixing the two techniques is confusing. You can't use the "accumulate" technique with functions designed for the "check separately" technique. You can use the "check separately" technique with functions designed for the "accumulate" technique, but then error_set() can't catch you setting an error more than once. Standardize on the "check separately" technique for now, because it's overwhelmingly prevalent. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
2014-05-07 11:53:54 +04:00
assert(v->type == VISITOR_INPUT || (value >= min && value <= max));
if (!v->type_int64(v, name, &value, errp)) {
return false;
}
if (value < min || value > max) {
assert(v->type == VISITOR_INPUT);
error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
name ? name : "null", type);
return false;
}
*obj = value;
return true;
}
bool visit_type_int8(Visitor *v, const char *name, int8_t *obj, Error **errp)
{
int64_t value;
bool ok;
trace_visit_type_int8(v, name, obj);
value = *obj;
ok = visit_type_intN(v, &value, name, INT8_MIN, INT8_MAX, "int8_t", errp);
*obj = value;
return ok;
}
qapi: Replace uncommon use of the error API by the common one We commonly use the error API like this: err = NULL; foo(..., &err); if (err) { goto out; } bar(..., &err); Every error source is checked separately. The second function is only called when the first one succeeds. Both functions are free to pass their argument to error_set(). Because error_set() asserts no error has been set, this effectively means they must not be called with an error set. The qapi-generated code uses the error API differently: // *errp was initialized to NULL somewhere up the call chain frob(..., errp); gnat(..., errp); Errors accumulate in *errp: first error wins, subsequent errors get dropped. To make this work, the second function does nothing when called with an error set. Requires non-null errp, or else the second function can't see the first one fail. This usage has also bled into visitor tests, and two device model object property getters rtc_get_date() and balloon_stats_get_all(). With the "accumulate" technique, you need fewer error checks in callers, and buy that with an error check in every callee. Can be nice. However, mixing the two techniques is confusing. You can't use the "accumulate" technique with functions designed for the "check separately" technique. You can use the "check separately" technique with functions designed for the "accumulate" technique, but then error_set() can't catch you setting an error more than once. Standardize on the "check separately" technique for now, because it's overwhelmingly prevalent. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
2014-05-07 11:53:54 +04:00
bool visit_type_int16(Visitor *v, const char *name, int16_t *obj,
qapi: Swap visit_* arguments for consistent 'name' placement JSON uses "name":value, but many of our visitor interfaces were called with visit_type_FOO(v, &value, name, errp). This can be a bit confusing to have to mentally swap the parameter order to match JSON order. It's particularly bad for visit_start_struct(), where the 'name' parameter is smack in the middle of the otherwise-related group of 'obj, kind, size' parameters! It's time to do a global swap of the parameter ordering, so that the 'name' parameter is always immediately after the Visitor argument. Additional reason in favor of the swap: the existing include/qjson.h prefers listing 'name' first in json_prop_*(), and I have plans to unify that file with the qapi visitors; listing 'name' first in qapi will minimize churn to the (admittedly few) qjson.h clients. Later patches will then fix docs, object.h, visitor-impl.h, and those clients to match. Done by first patching scripts/qapi*.py by hand to make generated files do what I want, then by running the following Coccinelle script to affect the rest of the code base: $ spatch --sp-file script `git grep -l '\bvisit_' -- '**/*.[ch]'` I then had to apply some touchups (Coccinelle insisted on TAB indentation in visitor.h, and botched the signature of visit_type_enum() by rewriting 'const char *const strings[]' to the syntactically invalid 'const char*const[] strings'). The movement of parameters is sufficient to provoke compiler errors if any callers were missed. // Part 1: Swap declaration order @@ type TV, TErr, TObj, T1, T2; identifier OBJ, ARG1, ARG2; @@ void visit_start_struct -(TV v, TObj OBJ, T1 ARG1, const char *name, T2 ARG2, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, T2 ARG2, TErr errp) { ... } @@ type bool, TV, T1; identifier ARG1; @@ bool visit_optional -(TV v, T1 ARG1, const char *name) +(TV v, const char *name, T1 ARG1) { ... } @@ type TV, TErr, TObj, T1; identifier OBJ, ARG1; @@ void visit_get_next_type -(TV v, TObj OBJ, T1 ARG1, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, TErr errp) { ... } @@ type TV, TErr, TObj, T1, T2; identifier OBJ, ARG1, ARG2; @@ void visit_type_enum -(TV v, TObj OBJ, T1 ARG1, T2 ARG2, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, T2 ARG2, TErr errp) { ... } @@ type TV, TErr, TObj; identifier OBJ; identifier VISIT_TYPE =~ "^visit_type_"; @@ void VISIT_TYPE -(TV v, TObj OBJ, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, TErr errp) { ... } // Part 2: swap caller order @@ expression V, NAME, OBJ, ARG1, ARG2, ERR; identifier VISIT_TYPE =~ "^visit_type_"; @@ ( -visit_start_struct(V, OBJ, ARG1, NAME, ARG2, ERR) +visit_start_struct(V, NAME, OBJ, ARG1, ARG2, ERR) | -visit_optional(V, ARG1, NAME) +visit_optional(V, NAME, ARG1) | -visit_get_next_type(V, OBJ, ARG1, NAME, ERR) +visit_get_next_type(V, NAME, OBJ, ARG1, ERR) | -visit_type_enum(V, OBJ, ARG1, ARG2, NAME, ERR) +visit_type_enum(V, NAME, OBJ, ARG1, ARG2, ERR) | -VISIT_TYPE(V, OBJ, NAME, ERR) +VISIT_TYPE(V, NAME, OBJ, ERR) ) Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-Id: <1454075341-13658-19-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-01-29 16:48:54 +03:00
Error **errp)
{
int64_t value;
bool ok;
trace_visit_type_int16(v, name, obj);
value = *obj;
ok = visit_type_intN(v, &value, name, INT16_MIN, INT16_MAX, "int16_t",
errp);
*obj = value;
return ok;
}
bool visit_type_int32(Visitor *v, const char *name, int32_t *obj,
qapi: Swap visit_* arguments for consistent 'name' placement JSON uses "name":value, but many of our visitor interfaces were called with visit_type_FOO(v, &value, name, errp). This can be a bit confusing to have to mentally swap the parameter order to match JSON order. It's particularly bad for visit_start_struct(), where the 'name' parameter is smack in the middle of the otherwise-related group of 'obj, kind, size' parameters! It's time to do a global swap of the parameter ordering, so that the 'name' parameter is always immediately after the Visitor argument. Additional reason in favor of the swap: the existing include/qjson.h prefers listing 'name' first in json_prop_*(), and I have plans to unify that file with the qapi visitors; listing 'name' first in qapi will minimize churn to the (admittedly few) qjson.h clients. Later patches will then fix docs, object.h, visitor-impl.h, and those clients to match. Done by first patching scripts/qapi*.py by hand to make generated files do what I want, then by running the following Coccinelle script to affect the rest of the code base: $ spatch --sp-file script `git grep -l '\bvisit_' -- '**/*.[ch]'` I then had to apply some touchups (Coccinelle insisted on TAB indentation in visitor.h, and botched the signature of visit_type_enum() by rewriting 'const char *const strings[]' to the syntactically invalid 'const char*const[] strings'). The movement of parameters is sufficient to provoke compiler errors if any callers were missed. // Part 1: Swap declaration order @@ type TV, TErr, TObj, T1, T2; identifier OBJ, ARG1, ARG2; @@ void visit_start_struct -(TV v, TObj OBJ, T1 ARG1, const char *name, T2 ARG2, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, T2 ARG2, TErr errp) { ... } @@ type bool, TV, T1; identifier ARG1; @@ bool visit_optional -(TV v, T1 ARG1, const char *name) +(TV v, const char *name, T1 ARG1) { ... } @@ type TV, TErr, TObj, T1; identifier OBJ, ARG1; @@ void visit_get_next_type -(TV v, TObj OBJ, T1 ARG1, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, TErr errp) { ... } @@ type TV, TErr, TObj, T1, T2; identifier OBJ, ARG1, ARG2; @@ void visit_type_enum -(TV v, TObj OBJ, T1 ARG1, T2 ARG2, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, T2 ARG2, TErr errp) { ... } @@ type TV, TErr, TObj; identifier OBJ; identifier VISIT_TYPE =~ "^visit_type_"; @@ void VISIT_TYPE -(TV v, TObj OBJ, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, TErr errp) { ... } // Part 2: swap caller order @@ expression V, NAME, OBJ, ARG1, ARG2, ERR; identifier VISIT_TYPE =~ "^visit_type_"; @@ ( -visit_start_struct(V, OBJ, ARG1, NAME, ARG2, ERR) +visit_start_struct(V, NAME, OBJ, ARG1, ARG2, ERR) | -visit_optional(V, ARG1, NAME) +visit_optional(V, NAME, ARG1) | -visit_get_next_type(V, OBJ, ARG1, NAME, ERR) +visit_get_next_type(V, NAME, OBJ, ARG1, ERR) | -visit_type_enum(V, OBJ, ARG1, ARG2, NAME, ERR) +visit_type_enum(V, NAME, OBJ, ARG1, ARG2, ERR) | -VISIT_TYPE(V, OBJ, NAME, ERR) +VISIT_TYPE(V, NAME, OBJ, ERR) ) Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-Id: <1454075341-13658-19-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-01-29 16:48:54 +03:00
Error **errp)
{
int64_t value;
bool ok;
trace_visit_type_int32(v, name, obj);
value = *obj;
ok = visit_type_intN(v, &value, name, INT32_MIN, INT32_MAX, "int32_t",
errp);
*obj = value;
return ok;
}
bool visit_type_int64(Visitor *v, const char *name, int64_t *obj,
qapi: Swap visit_* arguments for consistent 'name' placement JSON uses "name":value, but many of our visitor interfaces were called with visit_type_FOO(v, &value, name, errp). This can be a bit confusing to have to mentally swap the parameter order to match JSON order. It's particularly bad for visit_start_struct(), where the 'name' parameter is smack in the middle of the otherwise-related group of 'obj, kind, size' parameters! It's time to do a global swap of the parameter ordering, so that the 'name' parameter is always immediately after the Visitor argument. Additional reason in favor of the swap: the existing include/qjson.h prefers listing 'name' first in json_prop_*(), and I have plans to unify that file with the qapi visitors; listing 'name' first in qapi will minimize churn to the (admittedly few) qjson.h clients. Later patches will then fix docs, object.h, visitor-impl.h, and those clients to match. Done by first patching scripts/qapi*.py by hand to make generated files do what I want, then by running the following Coccinelle script to affect the rest of the code base: $ spatch --sp-file script `git grep -l '\bvisit_' -- '**/*.[ch]'` I then had to apply some touchups (Coccinelle insisted on TAB indentation in visitor.h, and botched the signature of visit_type_enum() by rewriting 'const char *const strings[]' to the syntactically invalid 'const char*const[] strings'). The movement of parameters is sufficient to provoke compiler errors if any callers were missed. // Part 1: Swap declaration order @@ type TV, TErr, TObj, T1, T2; identifier OBJ, ARG1, ARG2; @@ void visit_start_struct -(TV v, TObj OBJ, T1 ARG1, const char *name, T2 ARG2, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, T2 ARG2, TErr errp) { ... } @@ type bool, TV, T1; identifier ARG1; @@ bool visit_optional -(TV v, T1 ARG1, const char *name) +(TV v, const char *name, T1 ARG1) { ... } @@ type TV, TErr, TObj, T1; identifier OBJ, ARG1; @@ void visit_get_next_type -(TV v, TObj OBJ, T1 ARG1, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, TErr errp) { ... } @@ type TV, TErr, TObj, T1, T2; identifier OBJ, ARG1, ARG2; @@ void visit_type_enum -(TV v, TObj OBJ, T1 ARG1, T2 ARG2, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, T2 ARG2, TErr errp) { ... } @@ type TV, TErr, TObj; identifier OBJ; identifier VISIT_TYPE =~ "^visit_type_"; @@ void VISIT_TYPE -(TV v, TObj OBJ, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, TErr errp) { ... } // Part 2: swap caller order @@ expression V, NAME, OBJ, ARG1, ARG2, ERR; identifier VISIT_TYPE =~ "^visit_type_"; @@ ( -visit_start_struct(V, OBJ, ARG1, NAME, ARG2, ERR) +visit_start_struct(V, NAME, OBJ, ARG1, ARG2, ERR) | -visit_optional(V, ARG1, NAME) +visit_optional(V, NAME, ARG1) | -visit_get_next_type(V, OBJ, ARG1, NAME, ERR) +visit_get_next_type(V, NAME, OBJ, ARG1, ERR) | -visit_type_enum(V, OBJ, ARG1, ARG2, NAME, ERR) +visit_type_enum(V, NAME, OBJ, ARG1, ARG2, ERR) | -VISIT_TYPE(V, OBJ, NAME, ERR) +VISIT_TYPE(V, NAME, OBJ, ERR) ) Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-Id: <1454075341-13658-19-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-01-29 16:48:54 +03:00
Error **errp)
{
assert(obj);
trace_visit_type_int64(v, name, obj);
return v->type_int64(v, name, obj, errp);
}
bool visit_type_size(Visitor *v, const char *name, uint64_t *obj,
qapi: Swap visit_* arguments for consistent 'name' placement JSON uses "name":value, but many of our visitor interfaces were called with visit_type_FOO(v, &value, name, errp). This can be a bit confusing to have to mentally swap the parameter order to match JSON order. It's particularly bad for visit_start_struct(), where the 'name' parameter is smack in the middle of the otherwise-related group of 'obj, kind, size' parameters! It's time to do a global swap of the parameter ordering, so that the 'name' parameter is always immediately after the Visitor argument. Additional reason in favor of the swap: the existing include/qjson.h prefers listing 'name' first in json_prop_*(), and I have plans to unify that file with the qapi visitors; listing 'name' first in qapi will minimize churn to the (admittedly few) qjson.h clients. Later patches will then fix docs, object.h, visitor-impl.h, and those clients to match. Done by first patching scripts/qapi*.py by hand to make generated files do what I want, then by running the following Coccinelle script to affect the rest of the code base: $ spatch --sp-file script `git grep -l '\bvisit_' -- '**/*.[ch]'` I then had to apply some touchups (Coccinelle insisted on TAB indentation in visitor.h, and botched the signature of visit_type_enum() by rewriting 'const char *const strings[]' to the syntactically invalid 'const char*const[] strings'). The movement of parameters is sufficient to provoke compiler errors if any callers were missed. // Part 1: Swap declaration order @@ type TV, TErr, TObj, T1, T2; identifier OBJ, ARG1, ARG2; @@ void visit_start_struct -(TV v, TObj OBJ, T1 ARG1, const char *name, T2 ARG2, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, T2 ARG2, TErr errp) { ... } @@ type bool, TV, T1; identifier ARG1; @@ bool visit_optional -(TV v, T1 ARG1, const char *name) +(TV v, const char *name, T1 ARG1) { ... } @@ type TV, TErr, TObj, T1; identifier OBJ, ARG1; @@ void visit_get_next_type -(TV v, TObj OBJ, T1 ARG1, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, TErr errp) { ... } @@ type TV, TErr, TObj, T1, T2; identifier OBJ, ARG1, ARG2; @@ void visit_type_enum -(TV v, TObj OBJ, T1 ARG1, T2 ARG2, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, T2 ARG2, TErr errp) { ... } @@ type TV, TErr, TObj; identifier OBJ; identifier VISIT_TYPE =~ "^visit_type_"; @@ void VISIT_TYPE -(TV v, TObj OBJ, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, TErr errp) { ... } // Part 2: swap caller order @@ expression V, NAME, OBJ, ARG1, ARG2, ERR; identifier VISIT_TYPE =~ "^visit_type_"; @@ ( -visit_start_struct(V, OBJ, ARG1, NAME, ARG2, ERR) +visit_start_struct(V, NAME, OBJ, ARG1, ARG2, ERR) | -visit_optional(V, ARG1, NAME) +visit_optional(V, NAME, ARG1) | -visit_get_next_type(V, OBJ, ARG1, NAME, ERR) +visit_get_next_type(V, NAME, OBJ, ARG1, ERR) | -visit_type_enum(V, OBJ, ARG1, ARG2, NAME, ERR) +visit_type_enum(V, NAME, OBJ, ARG1, ARG2, ERR) | -VISIT_TYPE(V, OBJ, NAME, ERR) +VISIT_TYPE(V, NAME, OBJ, ERR) ) Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-Id: <1454075341-13658-19-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-01-29 16:48:54 +03:00
Error **errp)
{
assert(obj);
trace_visit_type_size(v, name, obj);
qapi: Replace uncommon use of the error API by the common one We commonly use the error API like this: err = NULL; foo(..., &err); if (err) { goto out; } bar(..., &err); Every error source is checked separately. The second function is only called when the first one succeeds. Both functions are free to pass their argument to error_set(). Because error_set() asserts no error has been set, this effectively means they must not be called with an error set. The qapi-generated code uses the error API differently: // *errp was initialized to NULL somewhere up the call chain frob(..., errp); gnat(..., errp); Errors accumulate in *errp: first error wins, subsequent errors get dropped. To make this work, the second function does nothing when called with an error set. Requires non-null errp, or else the second function can't see the first one fail. This usage has also bled into visitor tests, and two device model object property getters rtc_get_date() and balloon_stats_get_all(). With the "accumulate" technique, you need fewer error checks in callers, and buy that with an error check in every callee. Can be nice. However, mixing the two techniques is confusing. You can't use the "accumulate" technique with functions designed for the "check separately" technique. You can use the "check separately" technique with functions designed for the "accumulate" technique, but then error_set() can't catch you setting an error more than once. Standardize on the "check separately" technique for now, because it's overwhelmingly prevalent. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
2014-05-07 11:53:54 +04:00
if (v->type_size) {
return v->type_size(v, name, obj, errp);
}
return v->type_uint64(v, name, obj, errp);
}
bool visit_type_bool(Visitor *v, const char *name, bool *obj, Error **errp)
{
assert(obj);
trace_visit_type_bool(v, name, obj);
return v->type_bool(v, name, obj, errp);
}
bool visit_type_str(Visitor *v, const char *name, char **obj, Error **errp)
{
bool ok;
assert(obj);
/* TODO: Fix callers to not pass NULL when they mean "", so that we
* can enable:
qapi: Add new clone visitor We have a couple places in the code base that want to deep-clone one QAPI object into another, and they were resorting to serializing the struct out to QObject then reparsing it. A much more efficient version can be done by adding a new clone visitor. Since cloning is still relatively uncommon, expose the use of the new visitor via a QAPI_CLONE() macro that takes care of type-punning the underlying function pointer, rather than generating lots of unused functions for types that won't be cloned. And yes, we're relying on the compiler treating all pointers equally, even though a strict C program cannot portably do so - but we're not the first one in the qemu code base to expect it to work (hello, glib!). The choice of adding a fourth visitor type deserves some explanation. On the surface, the clone visitor is mostly an input visitor (it takes arbitrary input - in this case, another QAPI object - and creates a new QAPI object during the course of the visit). But ever since commit da72ab0 consolidated enum visits based on the visitor type, using VISITOR_INPUT would cause us to run visit_type_str(), even though for cloning there is nothing to do (we just copy the enum value across, without regards to its mapping to strings). Also, since our input happens to be a QAPI object, we can also satisfy the internal checks for VISITOR_OUTPUT. So in the end, I settled with a new VISITOR_CLONE, and chose its value such that many internal checks can use 'v->type & mask', sticking to 'v->type == value' where the difference matters. Note that we can only clone objects (including alternates) and lists, not built-ins or enums. The visitor core hides integer width from the actual visitor (since commit 04e070d), and as long as that's the case, we can't clone top-level integers. Then again, those can always be cloned by direct copy, since they are not objects with deep pointers, so it's no real loss. And restricting cloning to just objects and lists is cleaner than restricting it to non-integers. As such, I documented that the clone visitor is for direct use only by code internal to QAPI, and should not be used on incomplete objects (other than a hack to work around the fact that we allow NULL in place of "" in visit_type_str() in other output visitors). Note that as written, the clone visitor will never fail on a complete object. Scalars (including enums) not at the root of the clone copy just fine with no additional effort while visiting the scalar, by virtue of a g_memdup() each time we push another struct onto the stack. Cloning a string requires deduplication of a pointer, which means it can also provide the guarantee of an input visitor of never producing NULL even when still accepting NULL in place of "" the way the QMP output visitor does. Cloning an 'any' type could be possible by incrementing the QObject refcnt, but it's not obvious whether that is better than implementing a QObject deep clone. So for now, we document it as unsupported, and intentionally omit the .type_any() callback to let a developer know their usage needs implementation. Add testsuite coverage for several different clone situations, to ensure that the code is working. I also tested that valgrind was happy with the test. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1465490926-28625-14-git-send-email-eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:44 +03:00
assert(!(v->type & VISITOR_OUTPUT) || *obj);
*/
trace_visit_type_str(v, name, obj);
ok = v->type_str(v, name, obj, errp);
qapi: Add new clone visitor We have a couple places in the code base that want to deep-clone one QAPI object into another, and they were resorting to serializing the struct out to QObject then reparsing it. A much more efficient version can be done by adding a new clone visitor. Since cloning is still relatively uncommon, expose the use of the new visitor via a QAPI_CLONE() macro that takes care of type-punning the underlying function pointer, rather than generating lots of unused functions for types that won't be cloned. And yes, we're relying on the compiler treating all pointers equally, even though a strict C program cannot portably do so - but we're not the first one in the qemu code base to expect it to work (hello, glib!). The choice of adding a fourth visitor type deserves some explanation. On the surface, the clone visitor is mostly an input visitor (it takes arbitrary input - in this case, another QAPI object - and creates a new QAPI object during the course of the visit). But ever since commit da72ab0 consolidated enum visits based on the visitor type, using VISITOR_INPUT would cause us to run visit_type_str(), even though for cloning there is nothing to do (we just copy the enum value across, without regards to its mapping to strings). Also, since our input happens to be a QAPI object, we can also satisfy the internal checks for VISITOR_OUTPUT. So in the end, I settled with a new VISITOR_CLONE, and chose its value such that many internal checks can use 'v->type & mask', sticking to 'v->type == value' where the difference matters. Note that we can only clone objects (including alternates) and lists, not built-ins or enums. The visitor core hides integer width from the actual visitor (since commit 04e070d), and as long as that's the case, we can't clone top-level integers. Then again, those can always be cloned by direct copy, since they are not objects with deep pointers, so it's no real loss. And restricting cloning to just objects and lists is cleaner than restricting it to non-integers. As such, I documented that the clone visitor is for direct use only by code internal to QAPI, and should not be used on incomplete objects (other than a hack to work around the fact that we allow NULL in place of "" in visit_type_str() in other output visitors). Note that as written, the clone visitor will never fail on a complete object. Scalars (including enums) not at the root of the clone copy just fine with no additional effort while visiting the scalar, by virtue of a g_memdup() each time we push another struct onto the stack. Cloning a string requires deduplication of a pointer, which means it can also provide the guarantee of an input visitor of never producing NULL even when still accepting NULL in place of "" the way the QMP output visitor does. Cloning an 'any' type could be possible by incrementing the QObject refcnt, but it's not obvious whether that is better than implementing a QObject deep clone. So for now, we document it as unsupported, and intentionally omit the .type_any() callback to let a developer know their usage needs implementation. Add testsuite coverage for several different clone situations, to ensure that the code is working. I also tested that valgrind was happy with the test. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1465490926-28625-14-git-send-email-eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:44 +03:00
if (v->type & VISITOR_INPUT) {
assert(ok != !*obj);
}
return ok;
}
bool visit_type_number(Visitor *v, const char *name, double *obj,
qapi: Swap visit_* arguments for consistent 'name' placement JSON uses "name":value, but many of our visitor interfaces were called with visit_type_FOO(v, &value, name, errp). This can be a bit confusing to have to mentally swap the parameter order to match JSON order. It's particularly bad for visit_start_struct(), where the 'name' parameter is smack in the middle of the otherwise-related group of 'obj, kind, size' parameters! It's time to do a global swap of the parameter ordering, so that the 'name' parameter is always immediately after the Visitor argument. Additional reason in favor of the swap: the existing include/qjson.h prefers listing 'name' first in json_prop_*(), and I have plans to unify that file with the qapi visitors; listing 'name' first in qapi will minimize churn to the (admittedly few) qjson.h clients. Later patches will then fix docs, object.h, visitor-impl.h, and those clients to match. Done by first patching scripts/qapi*.py by hand to make generated files do what I want, then by running the following Coccinelle script to affect the rest of the code base: $ spatch --sp-file script `git grep -l '\bvisit_' -- '**/*.[ch]'` I then had to apply some touchups (Coccinelle insisted on TAB indentation in visitor.h, and botched the signature of visit_type_enum() by rewriting 'const char *const strings[]' to the syntactically invalid 'const char*const[] strings'). The movement of parameters is sufficient to provoke compiler errors if any callers were missed. // Part 1: Swap declaration order @@ type TV, TErr, TObj, T1, T2; identifier OBJ, ARG1, ARG2; @@ void visit_start_struct -(TV v, TObj OBJ, T1 ARG1, const char *name, T2 ARG2, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, T2 ARG2, TErr errp) { ... } @@ type bool, TV, T1; identifier ARG1; @@ bool visit_optional -(TV v, T1 ARG1, const char *name) +(TV v, const char *name, T1 ARG1) { ... } @@ type TV, TErr, TObj, T1; identifier OBJ, ARG1; @@ void visit_get_next_type -(TV v, TObj OBJ, T1 ARG1, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, TErr errp) { ... } @@ type TV, TErr, TObj, T1, T2; identifier OBJ, ARG1, ARG2; @@ void visit_type_enum -(TV v, TObj OBJ, T1 ARG1, T2 ARG2, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, T1 ARG1, T2 ARG2, TErr errp) { ... } @@ type TV, TErr, TObj; identifier OBJ; identifier VISIT_TYPE =~ "^visit_type_"; @@ void VISIT_TYPE -(TV v, TObj OBJ, const char *name, TErr errp) +(TV v, const char *name, TObj OBJ, TErr errp) { ... } // Part 2: swap caller order @@ expression V, NAME, OBJ, ARG1, ARG2, ERR; identifier VISIT_TYPE =~ "^visit_type_"; @@ ( -visit_start_struct(V, OBJ, ARG1, NAME, ARG2, ERR) +visit_start_struct(V, NAME, OBJ, ARG1, ARG2, ERR) | -visit_optional(V, ARG1, NAME) +visit_optional(V, NAME, ARG1) | -visit_get_next_type(V, OBJ, ARG1, NAME, ERR) +visit_get_next_type(V, NAME, OBJ, ARG1, ERR) | -visit_type_enum(V, OBJ, ARG1, ARG2, NAME, ERR) +visit_type_enum(V, NAME, OBJ, ARG1, ARG2, ERR) | -VISIT_TYPE(V, OBJ, NAME, ERR) +VISIT_TYPE(V, NAME, OBJ, ERR) ) Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-Id: <1454075341-13658-19-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-01-29 16:48:54 +03:00
Error **errp)
{
assert(obj);
trace_visit_type_number(v, name, obj);
return v->type_number(v, name, obj, errp);
}
bool visit_type_any(Visitor *v, const char *name, QObject **obj, Error **errp)
{
bool ok;
assert(obj);
assert(v->type != VISITOR_OUTPUT || *obj);
trace_visit_type_any(v, name, obj);
ok = v->type_any(v, name, obj, errp);
if (v->type == VISITOR_INPUT) {
assert(ok != !*obj);
}
return ok;
}
bool visit_type_null(Visitor *v, const char *name, QNull **obj,
Error **errp)
2016-04-29 00:45:22 +03:00
{
trace_visit_type_null(v, name, obj);
return v->type_null(v, name, obj, errp);
2016-04-29 00:45:22 +03:00
}
static bool output_type_enum(Visitor *v, const char *name, int *obj,
const QEnumLookup *lookup, Error **errp)
{
int value = *obj;
char *enum_str;
enum_str = (char *)qapi_enum_lookup(lookup, value);
return visit_type_str(v, name, &enum_str, errp);
}
static bool input_type_enum(Visitor *v, const char *name, int *obj,
const QEnumLookup *lookup, Error **errp)
{
int64_t value;
char *enum_str;
if (!visit_type_str(v, name, &enum_str, errp)) {
return false;
}
value = qapi_enum_parse(lookup, enum_str, -1, NULL);
if (value < 0) {
error_setg(errp, QERR_INVALID_PARAMETER, enum_str);
g_free(enum_str);
return false;
}
g_free(enum_str);
*obj = value;
return true;
}
bool visit_type_enum(Visitor *v, const char *name, int *obj,
const QEnumLookup *lookup, Error **errp)
{
assert(obj && lookup);
trace_visit_type_enum(v, name, obj);
qapi: Add new clone visitor We have a couple places in the code base that want to deep-clone one QAPI object into another, and they were resorting to serializing the struct out to QObject then reparsing it. A much more efficient version can be done by adding a new clone visitor. Since cloning is still relatively uncommon, expose the use of the new visitor via a QAPI_CLONE() macro that takes care of type-punning the underlying function pointer, rather than generating lots of unused functions for types that won't be cloned. And yes, we're relying on the compiler treating all pointers equally, even though a strict C program cannot portably do so - but we're not the first one in the qemu code base to expect it to work (hello, glib!). The choice of adding a fourth visitor type deserves some explanation. On the surface, the clone visitor is mostly an input visitor (it takes arbitrary input - in this case, another QAPI object - and creates a new QAPI object during the course of the visit). But ever since commit da72ab0 consolidated enum visits based on the visitor type, using VISITOR_INPUT would cause us to run visit_type_str(), even though for cloning there is nothing to do (we just copy the enum value across, without regards to its mapping to strings). Also, since our input happens to be a QAPI object, we can also satisfy the internal checks for VISITOR_OUTPUT. So in the end, I settled with a new VISITOR_CLONE, and chose its value such that many internal checks can use 'v->type & mask', sticking to 'v->type == value' where the difference matters. Note that we can only clone objects (including alternates) and lists, not built-ins or enums. The visitor core hides integer width from the actual visitor (since commit 04e070d), and as long as that's the case, we can't clone top-level integers. Then again, those can always be cloned by direct copy, since they are not objects with deep pointers, so it's no real loss. And restricting cloning to just objects and lists is cleaner than restricting it to non-integers. As such, I documented that the clone visitor is for direct use only by code internal to QAPI, and should not be used on incomplete objects (other than a hack to work around the fact that we allow NULL in place of "" in visit_type_str() in other output visitors). Note that as written, the clone visitor will never fail on a complete object. Scalars (including enums) not at the root of the clone copy just fine with no additional effort while visiting the scalar, by virtue of a g_memdup() each time we push another struct onto the stack. Cloning a string requires deduplication of a pointer, which means it can also provide the guarantee of an input visitor of never producing NULL even when still accepting NULL in place of "" the way the QMP output visitor does. Cloning an 'any' type could be possible by incrementing the QObject refcnt, but it's not obvious whether that is better than implementing a QObject deep clone. So for now, we document it as unsupported, and intentionally omit the .type_any() callback to let a developer know their usage needs implementation. Add testsuite coverage for several different clone situations, to ensure that the code is working. I also tested that valgrind was happy with the test. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1465490926-28625-14-git-send-email-eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:44 +03:00
switch (v->type) {
case VISITOR_INPUT:
return input_type_enum(v, name, obj, lookup, errp);
qapi: Add new clone visitor We have a couple places in the code base that want to deep-clone one QAPI object into another, and they were resorting to serializing the struct out to QObject then reparsing it. A much more efficient version can be done by adding a new clone visitor. Since cloning is still relatively uncommon, expose the use of the new visitor via a QAPI_CLONE() macro that takes care of type-punning the underlying function pointer, rather than generating lots of unused functions for types that won't be cloned. And yes, we're relying on the compiler treating all pointers equally, even though a strict C program cannot portably do so - but we're not the first one in the qemu code base to expect it to work (hello, glib!). The choice of adding a fourth visitor type deserves some explanation. On the surface, the clone visitor is mostly an input visitor (it takes arbitrary input - in this case, another QAPI object - and creates a new QAPI object during the course of the visit). But ever since commit da72ab0 consolidated enum visits based on the visitor type, using VISITOR_INPUT would cause us to run visit_type_str(), even though for cloning there is nothing to do (we just copy the enum value across, without regards to its mapping to strings). Also, since our input happens to be a QAPI object, we can also satisfy the internal checks for VISITOR_OUTPUT. So in the end, I settled with a new VISITOR_CLONE, and chose its value such that many internal checks can use 'v->type & mask', sticking to 'v->type == value' where the difference matters. Note that we can only clone objects (including alternates) and lists, not built-ins or enums. The visitor core hides integer width from the actual visitor (since commit 04e070d), and as long as that's the case, we can't clone top-level integers. Then again, those can always be cloned by direct copy, since they are not objects with deep pointers, so it's no real loss. And restricting cloning to just objects and lists is cleaner than restricting it to non-integers. As such, I documented that the clone visitor is for direct use only by code internal to QAPI, and should not be used on incomplete objects (other than a hack to work around the fact that we allow NULL in place of "" in visit_type_str() in other output visitors). Note that as written, the clone visitor will never fail on a complete object. Scalars (including enums) not at the root of the clone copy just fine with no additional effort while visiting the scalar, by virtue of a g_memdup() each time we push another struct onto the stack. Cloning a string requires deduplication of a pointer, which means it can also provide the guarantee of an input visitor of never producing NULL even when still accepting NULL in place of "" the way the QMP output visitor does. Cloning an 'any' type could be possible by incrementing the QObject refcnt, but it's not obvious whether that is better than implementing a QObject deep clone. So for now, we document it as unsupported, and intentionally omit the .type_any() callback to let a developer know their usage needs implementation. Add testsuite coverage for several different clone situations, to ensure that the code is working. I also tested that valgrind was happy with the test. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1465490926-28625-14-git-send-email-eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:44 +03:00
case VISITOR_OUTPUT:
return output_type_enum(v, name, obj, lookup, errp);
qapi: Add new clone visitor We have a couple places in the code base that want to deep-clone one QAPI object into another, and they were resorting to serializing the struct out to QObject then reparsing it. A much more efficient version can be done by adding a new clone visitor. Since cloning is still relatively uncommon, expose the use of the new visitor via a QAPI_CLONE() macro that takes care of type-punning the underlying function pointer, rather than generating lots of unused functions for types that won't be cloned. And yes, we're relying on the compiler treating all pointers equally, even though a strict C program cannot portably do so - but we're not the first one in the qemu code base to expect it to work (hello, glib!). The choice of adding a fourth visitor type deserves some explanation. On the surface, the clone visitor is mostly an input visitor (it takes arbitrary input - in this case, another QAPI object - and creates a new QAPI object during the course of the visit). But ever since commit da72ab0 consolidated enum visits based on the visitor type, using VISITOR_INPUT would cause us to run visit_type_str(), even though for cloning there is nothing to do (we just copy the enum value across, without regards to its mapping to strings). Also, since our input happens to be a QAPI object, we can also satisfy the internal checks for VISITOR_OUTPUT. So in the end, I settled with a new VISITOR_CLONE, and chose its value such that many internal checks can use 'v->type & mask', sticking to 'v->type == value' where the difference matters. Note that we can only clone objects (including alternates) and lists, not built-ins or enums. The visitor core hides integer width from the actual visitor (since commit 04e070d), and as long as that's the case, we can't clone top-level integers. Then again, those can always be cloned by direct copy, since they are not objects with deep pointers, so it's no real loss. And restricting cloning to just objects and lists is cleaner than restricting it to non-integers. As such, I documented that the clone visitor is for direct use only by code internal to QAPI, and should not be used on incomplete objects (other than a hack to work around the fact that we allow NULL in place of "" in visit_type_str() in other output visitors). Note that as written, the clone visitor will never fail on a complete object. Scalars (including enums) not at the root of the clone copy just fine with no additional effort while visiting the scalar, by virtue of a g_memdup() each time we push another struct onto the stack. Cloning a string requires deduplication of a pointer, which means it can also provide the guarantee of an input visitor of never producing NULL even when still accepting NULL in place of "" the way the QMP output visitor does. Cloning an 'any' type could be possible by incrementing the QObject refcnt, but it's not obvious whether that is better than implementing a QObject deep clone. So for now, we document it as unsupported, and intentionally omit the .type_any() callback to let a developer know their usage needs implementation. Add testsuite coverage for several different clone situations, to ensure that the code is working. I also tested that valgrind was happy with the test. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1465490926-28625-14-git-send-email-eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:44 +03:00
case VISITOR_CLONE:
/* nothing further to do, scalar value was already copied by
* g_memdup() during visit_start_*() */
return true;
qapi: Add new clone visitor We have a couple places in the code base that want to deep-clone one QAPI object into another, and they were resorting to serializing the struct out to QObject then reparsing it. A much more efficient version can be done by adding a new clone visitor. Since cloning is still relatively uncommon, expose the use of the new visitor via a QAPI_CLONE() macro that takes care of type-punning the underlying function pointer, rather than generating lots of unused functions for types that won't be cloned. And yes, we're relying on the compiler treating all pointers equally, even though a strict C program cannot portably do so - but we're not the first one in the qemu code base to expect it to work (hello, glib!). The choice of adding a fourth visitor type deserves some explanation. On the surface, the clone visitor is mostly an input visitor (it takes arbitrary input - in this case, another QAPI object - and creates a new QAPI object during the course of the visit). But ever since commit da72ab0 consolidated enum visits based on the visitor type, using VISITOR_INPUT would cause us to run visit_type_str(), even though for cloning there is nothing to do (we just copy the enum value across, without regards to its mapping to strings). Also, since our input happens to be a QAPI object, we can also satisfy the internal checks for VISITOR_OUTPUT. So in the end, I settled with a new VISITOR_CLONE, and chose its value such that many internal checks can use 'v->type & mask', sticking to 'v->type == value' where the difference matters. Note that we can only clone objects (including alternates) and lists, not built-ins or enums. The visitor core hides integer width from the actual visitor (since commit 04e070d), and as long as that's the case, we can't clone top-level integers. Then again, those can always be cloned by direct copy, since they are not objects with deep pointers, so it's no real loss. And restricting cloning to just objects and lists is cleaner than restricting it to non-integers. As such, I documented that the clone visitor is for direct use only by code internal to QAPI, and should not be used on incomplete objects (other than a hack to work around the fact that we allow NULL in place of "" in visit_type_str() in other output visitors). Note that as written, the clone visitor will never fail on a complete object. Scalars (including enums) not at the root of the clone copy just fine with no additional effort while visiting the scalar, by virtue of a g_memdup() each time we push another struct onto the stack. Cloning a string requires deduplication of a pointer, which means it can also provide the guarantee of an input visitor of never producing NULL even when still accepting NULL in place of "" the way the QMP output visitor does. Cloning an 'any' type could be possible by incrementing the QObject refcnt, but it's not obvious whether that is better than implementing a QObject deep clone. So for now, we document it as unsupported, and intentionally omit the .type_any() callback to let a developer know their usage needs implementation. Add testsuite coverage for several different clone situations, to ensure that the code is working. I also tested that valgrind was happy with the test. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1465490926-28625-14-git-send-email-eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:44 +03:00
case VISITOR_DEALLOC:
/* nothing to deallocate for a scalar */
return true;
default:
abort();
}
}