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qemu/scripts/qapi-visit.py
Markus Armbruster 297a3646c2 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>
2014-05-15 14:00:46 -04:00

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#
# QAPI visitor generator
#
# Copyright IBM, Corp. 2011
# Copyright (C) 2014 Red Hat, Inc.
#
# Authors:
# Anthony Liguori <aliguori@us.ibm.com>
# Michael Roth <mdroth@linux.vnet.ibm.com>
# Markus Armbruster <armbru@redhat.com>
#
# This work is licensed under the terms of the GNU GPL, version 2.
# See the COPYING file in the top-level directory.
from ordereddict import OrderedDict
from qapi import *
import re
import sys
import os
import getopt
import errno
implicit_structs = []
def generate_visit_implicit_struct(type):
global implicit_structs
if type in implicit_structs:
return ''
implicit_structs.append(type)
return mcgen('''
static void visit_type_implicit_%(c_type)s(Visitor *m, %(c_type)s **obj, Error **errp)
{
Error *err = NULL;
visit_start_implicit_struct(m, (void **)obj, sizeof(%(c_type)s), &err);
if (!err) {
visit_type_%(c_type)s_fields(m, obj, errp);
visit_end_implicit_struct(m, &err);
}
error_propagate(errp, err);
}
''',
c_type=type_name(type))
def generate_visit_struct_fields(name, field_prefix, fn_prefix, members, base = None):
substructs = []
ret = ''
if not fn_prefix:
full_name = name
else:
full_name = "%s_%s" % (name, fn_prefix)
for argname, argentry, optional, structured in parse_args(members):
if structured:
if not fn_prefix:
nested_fn_prefix = argname
else:
nested_fn_prefix = "%s_%s" % (fn_prefix, argname)
nested_field_prefix = "%s%s." % (field_prefix, argname)
ret += generate_visit_struct_fields(name, nested_field_prefix,
nested_fn_prefix, argentry)
ret += mcgen('''
static void visit_type_%(full_name)s_field_%(c_name)s(Visitor *m, %(name)s **obj, Error **errp)
{
''',
name=name, full_name=full_name, c_name=c_var(argname))
ret += generate_visit_struct_body(full_name, argname, argentry)
ret += mcgen('''
}
''')
if base:
ret += generate_visit_implicit_struct(base)
ret += mcgen('''
static void visit_type_%(full_name)s_fields(Visitor *m, %(name)s ** obj, Error **errp)
{
Error *err = NULL;
''',
name=name, full_name=full_name)
push_indent()
if base:
ret += mcgen('''
visit_type_implicit_%(type)s(m, &(*obj)->%(c_prefix)s%(c_name)s, &err);
if (err) {
goto out;
}
''',
c_prefix=c_var(field_prefix),
type=type_name(base), c_name=c_var('base'))
for argname, argentry, optional, structured in parse_args(members):
if optional:
ret += mcgen('''
visit_optional(m, &(*obj)->%(c_prefix)shas_%(c_name)s, "%(name)s", &err);
if (!err && (*obj)->%(prefix)shas_%(c_name)s) {
''',
c_prefix=c_var(field_prefix), prefix=field_prefix,
c_name=c_var(argname), name=argname)
push_indent()
if structured:
ret += mcgen('''
visit_type_%(full_name)s_field_%(c_name)s(m, obj, &err);
''',
full_name=full_name, c_name=c_var(argname))
else:
ret += mcgen('''
visit_type_%(type)s(m, &(*obj)->%(c_prefix)s%(c_name)s, "%(name)s", &err);
''',
c_prefix=c_var(field_prefix), prefix=field_prefix,
type=type_name(argentry), c_name=c_var(argname),
name=argname)
if optional:
pop_indent()
ret += mcgen('''
}
''')
ret += mcgen('''
if (err) {
goto out;
}
''')
pop_indent()
if re.search('^ *goto out\\;', ret, re.MULTILINE):
ret += mcgen('''
out:
''')
ret += mcgen('''
error_propagate(errp, err);
}
''')
return ret
def generate_visit_struct_body(field_prefix, name, members):
ret = mcgen('''
Error *err = NULL;
''')
if not field_prefix:
full_name = name
else:
full_name = "%s_%s" % (field_prefix, name)
if len(field_prefix):
ret += mcgen('''
visit_start_struct(m, NULL, "", "%(name)s", 0, &err);
''',
name=name)
else:
ret += mcgen('''
visit_start_struct(m, (void **)obj, "%(name)s", name, sizeof(%(name)s), &err);
''',
name=name)
ret += mcgen('''
if (!err) {
if (*obj) {
visit_type_%(name)s_fields(m, obj, errp);
}
visit_end_struct(m, &err);
}
error_propagate(errp, err);
''',
name=full_name)
return ret
def generate_visit_struct(expr):
name = expr['type']
members = expr['data']
base = expr.get('base')
ret = generate_visit_struct_fields(name, "", "", members, base)
ret += mcgen('''
void visit_type_%(name)s(Visitor *m, %(name)s ** obj, const char *name, Error **errp)
{
''',
name=name)
ret += generate_visit_struct_body("", name, members)
ret += mcgen('''
}
''')
return ret
def generate_visit_list(name, members):
return mcgen('''
void visit_type_%(name)sList(Visitor *m, %(name)sList ** obj, const char *name, Error **errp)
{
Error *err = NULL;
GenericList *i, **prev;
visit_start_list(m, name, &err);
if (err) {
goto out;
}
for (prev = (GenericList **)obj;
!err && (i = visit_next_list(m, prev, &err)) != NULL;
prev = &i) {
%(name)sList *native_i = (%(name)sList *)i;
visit_type_%(name)s(m, &native_i->value, NULL, &err);
}
error_propagate(errp, err);
err = NULL;
visit_end_list(m, &err);
out:
error_propagate(errp, err);
}
''',
name=name)
def generate_visit_enum(name, members):
return mcgen('''
void visit_type_%(name)s(Visitor *m, %(name)s * obj, const char *name, Error **errp)
{
visit_type_enum(m, (int *)obj, %(name)s_lookup, "%(name)s", name, errp);
}
''',
name=name)
def generate_visit_anon_union(name, members):
ret = mcgen('''
void visit_type_%(name)s(Visitor *m, %(name)s ** obj, const char *name, Error **errp)
{
Error *err = NULL;
visit_start_implicit_struct(m, (void**) obj, sizeof(%(name)s), &err);
if (err) {
goto out;
}
visit_get_next_type(m, (int*) &(*obj)->kind, %(name)s_qtypes, name, &err);
if (err) {
goto out_end;
}
switch ((*obj)->kind) {
''',
name=name)
# For anon union, always use the default enum type automatically generated
# as "'%sKind' % (name)"
disc_type = '%sKind' % (name)
for key in members:
assert (members[key] in builtin_types
or find_struct(members[key])
or find_union(members[key])), "Invalid anonymous union member"
enum_full_value = generate_enum_full_value(disc_type, key)
ret += mcgen('''
case %(enum_full_value)s:
visit_type_%(c_type)s(m, &(*obj)->%(c_name)s, name, &err);
break;
''',
enum_full_value = enum_full_value,
c_type = type_name(members[key]),
c_name = c_fun(key))
ret += mcgen('''
default:
abort();
}
out_end:
error_propagate(errp, err);
err = NULL;
visit_end_implicit_struct(m, &err);
out:
error_propagate(errp, err);
}
''')
return ret
def generate_visit_union(expr):
name = expr['union']
members = expr['data']
base = expr.get('base')
discriminator = expr.get('discriminator')
if discriminator == {}:
assert not base
return generate_visit_anon_union(name, members)
enum_define = discriminator_find_enum_define(expr)
if enum_define:
# Use the enum type as discriminator
ret = ""
disc_type = enum_define['enum_name']
else:
# There will always be a discriminator in the C switch code, by default it
# is an enum type generated silently as "'%sKind' % (name)"
ret = generate_visit_enum('%sKind' % name, members.keys())
disc_type = '%sKind' % (name)
if base:
base_fields = find_struct(base)['data']
if discriminator:
base_fields = base_fields.copy()
del base_fields[discriminator]
ret += generate_visit_struct_fields(name, "", "", base_fields)
if discriminator:
for key in members:
ret += generate_visit_implicit_struct(members[key])
ret += mcgen('''
void visit_type_%(name)s(Visitor *m, %(name)s ** obj, const char *name, Error **errp)
{
Error *err = NULL;
visit_start_struct(m, (void **)obj, "%(name)s", name, sizeof(%(name)s), &err);
if (err) {
goto out;
}
if (*obj) {
''',
name=name)
if base:
ret += mcgen('''
visit_type_%(name)s_fields(m, obj, &err);
if (err) {
goto out_obj;
}
''',
name=name)
if not discriminator:
disc_key = "type"
else:
disc_key = discriminator
ret += mcgen('''
visit_type_%(disc_type)s(m, &(*obj)->kind, "%(disc_key)s", &err);
if (err) {
goto out_obj;
}
switch ((*obj)->kind) {
''',
disc_type = disc_type,
disc_key = disc_key)
for key in members:
if not discriminator:
fmt = 'visit_type_%(c_type)s(m, &(*obj)->%(c_name)s, "data", &err);'
else:
fmt = 'visit_type_implicit_%(c_type)s(m, &(*obj)->%(c_name)s, &err);'
enum_full_value = generate_enum_full_value(disc_type, key)
ret += mcgen('''
case %(enum_full_value)s:
''' + fmt + '''
break;
''',
enum_full_value = enum_full_value,
c_type=type_name(members[key]),
c_name=c_fun(key))
ret += mcgen('''
default:
abort();
}
out_obj:
error_propagate(errp, err);
err = NULL;
}
visit_end_struct(m, &err);
out:
error_propagate(errp, err);
}
''')
return ret
def generate_declaration(name, members, genlist=True, builtin_type=False):
ret = ""
if not builtin_type:
ret += mcgen('''
void visit_type_%(name)s(Visitor *m, %(name)s ** obj, const char *name, Error **errp);
''',
name=name)
if genlist:
ret += mcgen('''
void visit_type_%(name)sList(Visitor *m, %(name)sList ** obj, const char *name, Error **errp);
''',
name=name)
return ret
def generate_enum_declaration(name, members, genlist=True):
ret = ""
if genlist:
ret += mcgen('''
void visit_type_%(name)sList(Visitor *m, %(name)sList ** obj, const char *name, Error **errp);
''',
name=name)
return ret
def generate_decl_enum(name, members, genlist=True):
return mcgen('''
void visit_type_%(name)s(Visitor *m, %(name)s * obj, const char *name, Error **errp);
''',
name=name)
try:
opts, args = getopt.gnu_getopt(sys.argv[1:], "chbp:i:o:",
["source", "header", "builtins", "prefix=",
"input-file=", "output-dir="])
except getopt.GetoptError, err:
print str(err)
sys.exit(1)
input_file = ""
output_dir = ""
prefix = ""
c_file = 'qapi-visit.c'
h_file = 'qapi-visit.h'
do_c = False
do_h = False
do_builtins = False
for o, a in opts:
if o in ("-p", "--prefix"):
prefix = a
elif o in ("-i", "--input-file"):
input_file = a
elif o in ("-o", "--output-dir"):
output_dir = a + "/"
elif o in ("-c", "--source"):
do_c = True
elif o in ("-h", "--header"):
do_h = True
elif o in ("-b", "--builtins"):
do_builtins = True
if not do_c and not do_h:
do_c = True
do_h = True
c_file = output_dir + prefix + c_file
h_file = output_dir + prefix + h_file
try:
os.makedirs(output_dir)
except os.error, e:
if e.errno != errno.EEXIST:
raise
def maybe_open(really, name, opt):
if really:
return open(name, opt)
else:
import StringIO
return StringIO.StringIO()
fdef = maybe_open(do_c, c_file, 'w')
fdecl = maybe_open(do_h, h_file, 'w')
fdef.write(mcgen('''
/* THIS FILE IS AUTOMATICALLY GENERATED, DO NOT MODIFY */
/*
* schema-defined QAPI visitor functions
*
* 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-common.h"
#include "%(header)s"
''',
header=basename(h_file)))
fdecl.write(mcgen('''
/* THIS FILE IS AUTOMATICALLY GENERATED, DO NOT MODIFY */
/*
* schema-defined QAPI visitor functions
*
* 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.
*
*/
#ifndef %(guard)s
#define %(guard)s
#include "qapi/visitor.h"
#include "%(prefix)sqapi-types.h"
''',
prefix=prefix, guard=guardname(h_file)))
exprs = parse_schema(input_file)
# to avoid header dependency hell, we always generate declarations
# for built-in types in our header files and simply guard them
fdecl.write(guardstart("QAPI_VISIT_BUILTIN_VISITOR_DECL"))
for typename in builtin_types:
fdecl.write(generate_declaration(typename, None, genlist=True,
builtin_type=True))
fdecl.write(guardend("QAPI_VISIT_BUILTIN_VISITOR_DECL"))
# ...this doesn't work for cases where we link in multiple objects that
# have the functions defined, so we use -b option to provide control
# over these cases
if do_builtins:
for typename in builtin_types:
fdef.write(generate_visit_list(typename, None))
for expr in exprs:
if expr.has_key('type'):
ret = generate_visit_struct(expr)
ret += generate_visit_list(expr['type'], expr['data'])
fdef.write(ret)
ret = generate_declaration(expr['type'], expr['data'])
fdecl.write(ret)
elif expr.has_key('union'):
ret = generate_visit_union(expr)
ret += generate_visit_list(expr['union'], expr['data'])
fdef.write(ret)
enum_define = discriminator_find_enum_define(expr)
ret = ""
if not enum_define:
ret = generate_decl_enum('%sKind' % expr['union'],
expr['data'].keys())
ret += generate_declaration(expr['union'], expr['data'])
fdecl.write(ret)
elif expr.has_key('enum'):
ret = generate_visit_list(expr['enum'], expr['data'])
ret += generate_visit_enum(expr['enum'], expr['data'])
fdef.write(ret)
ret = generate_decl_enum(expr['enum'], expr['data'])
ret += generate_enum_declaration(expr['enum'], expr['data'])
fdecl.write(ret)
fdecl.write('''
#endif
''')
fdecl.flush()
fdecl.close()
fdef.flush()
fdef.close()
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