To enable -Wformat-overflow=2, we need to clean up a couple of false
positives:
[2/5] Compiling C object tests/unit/test-qobject-output-visitor.p/test-qobject-output-visitor.c.o
../tests/unit/test-qobject-output-visitor.c: In function ‘test_visitor_out_list_struct’:
../tests/unit/test-qobject-output-visitor.c:577:28: error: ‘%.6f’ directive writing between 3 and 317 bytes into a region of size 32 [-Werror=format-overflow=]
577 | sprintf(expected, "%.6f", (double)i / 3);
| ^~~~
../tests/unit/test-qobject-output-visitor.c:577:27: note: assuming directive output of 8 bytes
577 | sprintf(expected, "%.6f", (double)i / 3);
| ^~~~~~
In file included from /usr/include/stdio.h:970,
from /home/me/q/var/qemu/include/qemu/osdep.h:114,
from ../tests/unit/test-qobject-output-visitor.c:13:
In function ‘sprintf’,
inlined from ‘test_visitor_out_list_struct’ at ../tests/unit/test-qobject-output-visitor.c:577:9:
/usr/include/bits/stdio2.h:30:10: note: ‘__builtin___sprintf_chk’ output between 4 and 318 bytes into a destination of size 32
30 | return __builtin___sprintf_chk (__s, __USE_FORTIFY_LEVEL - 1,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
31 | __glibc_objsize (__s), __fmt,
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
32 | __va_arg_pack ());
| ~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
FAILED: tests/unit/test-qobject-output-visitor.p/test-qobject-output-visitor.c.o
These buffers cannot actually overflow because the doubles are
between 0 and 31.0/3 inclusive.
However, formatting doubles just to compare them is silly. Compare
them directly instead. To avoid potential rounding trouble, change
the numbers tested to be representable exactly in double.
Signed-off-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20260305-nvme-v4-3-b65b9de1839f@rsg.ci.i.u-tokyo.ac.jp>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Akihiko OdakiandPhilippe Mathieu-Daudé
2a58162a1e