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>
Semantics of end_optional() differ subtly from the other end_FOO()
callbacks: when start_FOO() succeeds, the matching end_FOO() gets
called regardless of what happens in between. end_optional() gets
called only when everything in between succeeds as well. Entirely
undocumented, like all of the visitor API.
The only user of Visitor Callback end_optional() never did anything,
and was removed in commit 9f9ab46.
I'm about to clean up error handling in the generated visitor code,
and end_optional() is in my way. No users mean no test cases, and
making non-trivial cleanup transformations without test cases doesn't
strike me as a good idea.
Drop end_optional(), and rename start_optional() to optional(). We
can always go back to a pair of callbacks when we have an actual need.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Input and output marshalling functions do it differently. Change them
to work the same: initialize the I/O visitor, use it, clean it up,
initialize the dealloc visitor, use it, clean it up.
This delays dealloc visitor initialization in output marshalling
functions, and input visitor cleanup in input marshalling functions.
No functional change, but the latter will be convenient when I change
the error handling.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Use an explicit input file on the command-line instead of reading from standard
input.
It also outputs the proper file name when there's an error.
Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
The scripts carry this copyright notice:
# This work is licensed under the terms of the GNU GPLv2.
# See the COPYING.LIB file in the top-level directory.
The sentences contradict each other, as COPYING.LIB contains the LGPL
2.1. Michael Roth says this was a simple pasto, and he meant to refer
COPYING. Let's fix that.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
In qmp-marshal.c the dealloc visitor calls use the same errp
pointer of the input visitor calls. This means that if any of
the input visitor calls fails, then the dealloc visitor will
return early, before freeing the object's memory.
Here's an example, consider this code:
int qmp_marshal_input_block_passwd(Monitor *mon, const QDict *qdict, QObject **ret)
{
[...]
char * device = NULL;
char * password = NULL;
mi = qmp_input_visitor_new_strict(QOBJECT(args));
v = qmp_input_get_visitor(mi);
visit_type_str(v, &device, "device", errp);
visit_type_str(v, &password, "password", errp);
qmp_input_visitor_cleanup(mi);
if (error_is_set(errp)) {
goto out;
}
qmp_block_passwd(device, password, errp);
out:
md = qapi_dealloc_visitor_new();
v = qapi_dealloc_get_visitor(md);
visit_type_str(v, &device, "device", errp);
visit_type_str(v, &password, "password", errp);
qapi_dealloc_visitor_cleanup(md);
[...]
return 0;
}
Consider errp != NULL when the out label is reached, we're going
to leak device and password.
This patch fixes this by always passing errp=NULL for dealloc
visitors, meaning that we always try to free them regardless of
any previous failure. The above example would then be:
out:
md = qapi_dealloc_visitor_new();
v = qapi_dealloc_get_visitor(md);
visit_type_str(v, &device, "device", NULL);
visit_type_str(v, &password, "password", NULL);
qapi_dealloc_visitor_cleanup(md);
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
The file is only including error.h and qerror.h. Prefer explicit
inclusion of whatever files are needed.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
qmp-commands.h declares several functions that have arguments of
type QDict. However, qdict.h is not included. This will cause a
build breakage when a file includes qmp-commands.h but doesn't
include qdict.h.
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Options allow for changes in commands behavior. This commit introduces
the QCO_NO_SUCCESS_RESP option, which causes a command to not emit a
success response.
This is needed by commands such as qemu-ga's guest-shutdown, which
may not be able to complete before the VM vanishes. In this case, it's
useful and simpler not to bother sending a success response.
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
The fixes to qapi code generation had multiple bugs:
- the Null class used to drop output was missing some methods
- in some scripts it was never instantiated, leading to a None return,
which is missing even more methods
- the --source and --header options were swapped
Luckily, all those bugs were hidden by a makefile bug which caused the
old behaviour (with the race) to be invoked.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Make's multiple output syntax
x.c x.h: x.template
gen < x.template
actually invokes the command once for x.c and once for x.h (with differing $@
in each invocation). During a parallel build, the two commands may be invoked
in parallel; this opens up a race, where the second invocation trashes a file
supposedly produced during the first, and now in use by a dependent command.
The various qapi code generators are susceptible to this; fix by making them
generate just one file per invocation.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Today we generate something like this:
int qmp_marshal_input_query_foo(...)
...
retval = qmp_query_foo(errp);
qmp_marshal_output_query_foo(retval, ret, errp);
...
However, if qmp_query_foo() fails 'retval' will probably be NULL,
which can cause a segfault as not all visitors check if 'retval'
is valid.
This commit fixes that by changing the code generator to only
call the output marshal if qmp_query_foo() succeeds, like this:
retval = qmp_query_foo(errp);
if (!error_is_set(errp)) {
qmp_marshal_output_query_foo(retval, ret, errp);
}
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
To get the ball rolling merging QAPI, this patch introduces a "middle mode" to
the code generator. In middle mode, the code generator generates marshalling
functions that are compatible with the current QMP server. We absolutely need
to replace the current QMP server in order to support proper asynchronous
commands but using a middle mode provides a middle-ground that lets us start
converting commands in tree.
Note that all of the commands have been converted already in my glib branch.
Middle mode only exists until we finish merging them from my branch into the
main tree.
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Fixes a build issue on RHEL5, and potentially other distros, where gcc
will generate an error due to us not writing a trailing "\n" when
generating *qmp-commands.h
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This is the code generator for qapi command marshaling/dispatch.
Currently only generators for synchronous qapi/qmp functions are
supported. This script generates the following files:
$(prefix)qmp-marshal.c: command marshal/dispatch functions for each
QMP command defined in the schema. Functions
generated by qapi-visit.py are used to
convert qobjects recieved from the wire into
function parameters, and uses the same
visiter functions to convert native C return
values to qobjects from transmission back
over the wire.
$(prefix)qmp-commands.h: Function prototypes for the QMP commands
specified in the schema.
$(prefix) is used in the same manner as with qapi-types.py
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Luiz Capitulino <lcapitulino@gmail.com>
