The -Wstringop-truncation and -Wsizeof-pointer-memaccess warnings
I added and enhanced, respectively, in GCC 8 are arguably overly
strict for source arguments declared with the nonstring attribute.
For example, -Wsizeof-pointer-memaccess triggers for the strncat
call below:
__attribute__ ((nonstring)) char nonstr[8];
extern char *d;
strncat (d, nonstr, sizeof nonstr);
even though it's still a fairly common (if unsafe) idiom from
the early UNIX days (V7 from 1979 to be exact) where strncat
was introduced. (This use case, modulo the attribute, was
reduced from coreutils.)
Simialrly, -Wstringop-truncation warns for some strcat calls that
are actually safe, such as in:
strcpy (nonstr, "123");
strncat (d, nonstr, 32);
To help with the adoption of the warnings and the attribute and
avoid unnecessary churn the attached patch relaxes both warnings
to accept code like this without diagnostics.
The patch doesn't add any new warnings so I'd like it considered
for GCC 8 in addition to trunk.
Thanks
Martin