https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123024
Bug ID: 123024
Summary: -Wstringop-overread: bogus diagnostic about strncat(3)
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: [email protected]
Target Milestone: ---
In file included from /usr/include/string.h:548,
from /usr/include/x86_64-linux-gnu/bsd/string.h:28,
from logoutd.c:16:
In function ‘strncat’,
inlined from ‘main’ at logoutd.c:210:4:
/usr/include/x86_64-linux-gnu/bits/string_fortified.h:138:10: error:
‘__builtin___strncat_chk’ argument 2 declared attribute ‘nonstring’
[-Werror=stringop-overread]
138 | return __builtin___strncat_chk (__dest, __src, __len,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
139 | __glibc_objsize (__dest));
| ~~~~~~~~~~~~~~~~~~~~~~~~~
which is triggered by the following code:
char tty_name[sizeof(ut->ut_line) + 6]; // /dev/ +
NUL
...
if (strncmp(ut->ut_line, "/dev/", 5) != 0)
strcpy(tty_name, "/dev/");
else
strcpy(tty_name, "");
strncat_a(tty_name, ut->ut_line);
where strncat_a() is defined as
#define strncat_a(dst, src) strncat(dst, src, countof(src))
This is a totally valid strncat(3) call. Please move this out of
-Wstringop-overflow into something new such as -Wstrncat.
