| Message ID | 1454075341-13658-17-git-send-email-eblake@redhat.com |
|---|---|
| State | New |
| Headers | show |
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)
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> --- v10: s/tmp/value/, shorter commit message v9: mention earlier commit id, enhance commit message v8: no change v7: rebase on typo fix v6: new patch --- scripts/qapi-visit.py | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)