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authorEric Blake <eblake@redhat.com>2016-01-29 06:48:52 -0700
committerMarkus Armbruster <armbru@redhat.com>2016-02-08 17:29:55 +0100
commit395a233f7c089f23e3c0d43ce34c709dc5acd7de (patch)
tree698721f9d3101e5294cc10ab12bcbd0f67cdfe84
parent04e070d217b4414f1f91aa8ad25fc0ae7ca0be93 (diff)
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qapi: Don't cast Enum* to int*
C compilers are allowed to represent enums as a smaller type than int, if all enum values fit in the smaller type. There are even compiler flags that force the use of this smaller representation, although using them changes the ABI of a binary. Therefore, our generated code for visit_type_ENUM() (for all qapi enums) was wrong for casting Enum* to int* when calling visit_type_enum(). It appears that no one has been using compiler ABI switches for qemu, because if they had, we are potentially dereferencing beyond bounds or even risking a SIGBUS on platforms where unaligned pointer dereferencing is fatal. But it is still better to avoid the practice entirely, and just use the correct types. This matches the fix for alternate qapi types, done earlier in commit 0426d53 "qapi: Simplify visiting of alternate types", with generated code changing as: | void visit_type_QType(Visitor *v, QType *obj, const char *name, Error **errp) | { |- visit_type_enum(v, (int *)obj, QType_lookup, "QType", name, errp); |+ int value = *obj; |+ visit_type_enum(v, &value, QType_lookup, "QType", name, errp); |+ *obj = value; | } Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-Id: <1454075341-13658-17-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
-rw-r--r--scripts/qapi-visit.py5
1 files changed, 3 insertions, 2 deletions
diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index f98bb5f..ba75667 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -178,12 +178,13 @@ out:
def gen_visit_enum(name):
- # FIXME cast from enum *obj to int * invalidly assumes enum is int
return mcgen('''
void visit_type_%(c_name)s(Visitor *v, %(c_name)s *obj, const char *name, Error **errp)
{
- visit_type_enum(v, (int *)obj, %(c_name)s_lookup, "%(name)s", name, errp);
+ int value = *obj;
+ visit_type_enum(v, &value, %(c_name)s_lookup, "%(name)s", name, errp);
+ *obj = value;
}
''',
c_name=c_name(name), name=name)