On Tue, 12 Jun 2018, Martin Sebor wrote: > 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.)
I'm fine with backporting it. Richard.
