https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94021
Bug ID: 94021
Summary: -Werror=format-truncation= seems to cause incorrect
warning, thus error.
Product: gcc
Version: 9.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: ishikawa at yk dot rim.or.jp
Target Milestone: ---
Created attachment 47961
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47961&action=edit
preprocessed input file.
I am attaching the preprocessed source file,
and the exact command that produced the error.
And the error log in the following.
The crux of the "bogus" error is as follows.:
/NEW-SSD/NREF-COMM-CENTRAL/mozilla/comm/calendar/libical/src/libical/icaltimezone.c:1913:35:
error: ‘%02i’ directive output may be truncated writing 2 bytes into a region
of size between 1 and 5 [-Werror=format-truncation=]
1913 | snprintf (buffer, buffer_size, "%s%02i%02i%02i", sign, hours,
minutes, seconds);
| ^~~~~~~~~~~~~~~~
/NEW-SSD/NREF-COMM-CENTRAL/mozilla/comm/calendar/libical/src/libical/icaltimezone.c:1913:35:
note: directive argument in the range [0, 59]
/NEW-SSD/NREF-COMM-CENTRAL/mozilla/comm/calendar/libical/src/libical/icaltimezone.c:1913:35:
note: directive argument in the range [1, 59]
In file included from /usr/include/stdio.h:867,
from
/NEW-SSD/moz-obj-dir/objdir-tb3/dist/system_wrappers/stdio.h:3,
from
/NEW-SSD/NREF-COMM-CENTRAL/mozilla/comm/calendar/libical/src/libical/icaltimezone.c:34,
from Unified_c_libical_src_libical1.c:2:
/usr/include/x86_64-linux-gnu/bits/stdio2.h:67:10: note:
‘__builtin___snprintf_chk’ output between 8 and 12 bytes into a destination of
size 8
67 | return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
68 | __bos (__s), __fmt, __va_arg_pack ());
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from Unified_c_libical_src_libical1.c:2:
/NEW-SSD/NREF-COMM-CENTRAL/mozilla/comm/calendar/libical/src/libical/icaltimezone.c:1911:35:
error: ‘%02i’ directive output may be truncated writing 2 bytes into a region
of size between 1 and 5 [-Werror=format-truncation=]
1911 | snprintf (buffer, buffer_size, "%s%02i%02i", sign, hours, minutes);
| ^~~~~~~~~~~~
/NEW-SSD/NREF-COMM-CENTRAL/mozilla/comm/calendar/libical/src/libical/icaltimezone.c:1911:35:
note: directive argument in the range [0, 59]
In file included from /usr/include/stdio.h:867,
from
/NEW-SSD/moz-obj-dir/objdir-tb3/dist/system_wrappers/stdio.h:3,
from
/NEW-SSD/NREF-COMM-CENTRAL/mozilla/comm/calendar/libical/src/libical/icaltimezone.c:34,
from Unified_c_libical_src_libical1.c:2:
/usr/include/x86_64-linux-gnu/bits/stdio2.h:67:10: note:
‘__builtin___snprintf_chk’ output between 6 and 10 bytes into a destination of
size 8
67 | return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
68 | __bos (__s), __fmt, __va_arg_pack ());
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This comes from the source (unprocessed).: |sign| is either "+" or "-", and
the |hours|, |minutes|, and |seconds| are limited to [0,24), [0, 60).
if ((0 <= minutes && minutes <= 60) &&
(0 <= hours && hours <= 24) &&
(0 <= seconds && seconds <= 60)) {
if (seconds == 0)
snprintf (buffer, buffer_size, "%s%02i%02i", sign, hours, minutes);
else
snprintf (buffer, buffer_size, "%s%02i%02i%02i", sign, hours, minutes,
seconds);
} else {
Please note that in the error/warning message, the range is reported slightly
differently in a place.
/icaltimezone.c:1913:35: note: directive argument in the range [0, 59]
/NEW-SSD/NREF-COMM-CENTRAL/mozilla/comm/calendar/libical/src/libical/icaltimezone.c:1913:35:
note: directive argument in the range [1, 59]
I suspect some kind of internal data corruption.
A very simple program source code, t-snrpintf-issue.c does not cause the
problem to manifest. So I think the problem is caused by a combination of
large source file and maybe inlining?
The source code is part of mozilla thunderbird (its calendar subsystem).
In another instance where such error/warning was observed,
when I added the constraint of the form of
if ((0 <= minutes && minutes <= 60) &&
(0 <= hours && hours <= 24) &&
(0 <= seconds && seconds <= 60))
the compilation worked without the truncation error/warning message.
But here even though I added the if-expr to constrain the values to only two
decimal digits, the error/warning persists.
TIA
