On 06/11/2018 03:57 PM, Jeff Law wrote:
On 05/29/2018 08:57 PM, Martin Sebor wrote:
Warning for a strncpy call whose bound is the same as the size
of the source and suggesting to use the size of the source is
less than helpful when both sizes are the same, as in:
char a[4], b[4];
strncpy (a, b, sizeof b);
The attached patch suppresses the -Wsizeof-pointer-memaccess
warning for these cases. To do that even for VLAs (in some
cases), the patch enhances operand_equal_p() to handle
SAVE_EXPR to detect when VLA in sizeof VLA refers to the size
of a variable-length array.
Is this okay for trunk and GCC 8?
Martin
gcc-85931.diff
PR c/85931 - -Wsizeof-pointer-memaccess for strncpy with size of source
gcc/c-family/ChangeLog:
PR c/85931
* c-warn.c (sizeof_pointer_memaccess_warning): Avoid warning when
sizeof source and destination yields the same value.
gcc/ChangeLog:
PR c/85931
* fold-const.c (operand_equal_p): Handle SAVE_EXPR.
gcc/testsuite/ChangeLog:
PR c/85931
* gcc.dg/Wstringop-truncation-3.c: New test.
OK for the trunk. Richi and Jakub have the final say for the branch.
I'm a bit surprised that you don't just use operand_equal_p for both the
INTEGER_CST and !INTEGER_CST cases when testing dstsz == srcsz
It seemed that since the CST case compared the values of the size
expressions and the other case their lexicographic form they needed
to be different. But operand_equal_p() does value comparison for
constants so the conditional can be simplified by using just it
for both cases. Thanks for the suggestion! I've made that
simplification and committed r261515.
Jakub/Richard, can you please review the commit and let me know
if you have any concerns with backporting it to the GCC 8 branch?
(I will proceed if I don't hear anything this week.)
Thanks
Martin
