https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80537
Bug ID: 80537
Summary: missing -Wformat-overflow on POSIX %C conversion
specification
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
POSIX specifies that the %C conversion specification is equivalent to %lc (used
to format wide characters). The -Wformat-overflow doesn't recognize the %C
directive and doesn't issue warnings for it. Worse, the directive has the
effect of disabling the checking for the rest of the format string.
$ cat c.c && gcc -O2 -S -Wall -Wextra -Wpedantic c.c
char d[1];
void f (void)
{
__builtin_sprintf (d + 1, "%lc foo", 'a');
}
void g (void)
{
__builtin_sprintf (d + 1, "%C bar", 'a');
}
c.c: In function ‘g’:
c.c:10:31: warning: ISO C does not support the ‘%C’ gnu_printf format
[-Wformat=]
__builtin_sprintf (d + 1, "%C bar", 'a');
^
c.c: In function ‘f’:
c.c:5:30: warning: ‘%lc’ directive writing up to 1 bytes into a region of size
0 [-Wformat-overflow=]
__builtin_sprintf (d + 1, "%lc foo", 'a');
^~~
c.c:5:3: note: ‘__builtin_sprintf’ output between 5 and 6 bytes into a
destination of size 0
__builtin_sprintf (d + 1, "%lc foo", 'a');
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
