On 3/11/19 8:27 PM, Martin Sebor wrote:
The -Wstringop-truncation handling for strncpy/stpncpy neglects
to consider that character arrays tracked by the strlen pass
are not necessarily nul-terminated. It unconditionally adds
one when computing the size of each sequence to account for
the nul. This leads to false positive warnings when checking
the validity of indices/pointers computed by the built-ins.
The attached patch corrects this by adding one for the nul
only when the character array is known to be nul-terminated.
Since GCC 7 does not issue the warning this is a 8/9 regression
that I would like to fix in both releases. Is the patch okay
for trunk/gcc-8-branch?
Tested on x86_64-linux.
Martin
gcc-89644.diff
PR tree-optimization/89644 - False-positive -Warray-bounds diagnostic
on strncpy
gcc/ChangeLog:
PR tree-optimization/89644
* tree-ssa-strlen.c (handle_builtin_stxncpy): Consider unterminated
arrays in determining sequence sizes in strncpy and stpncpy.
gcc/testsuite/ChangeLog:
PR tree-optimization/89644
* gcc.dg/Wstringop-truncation-8.c: New test.
OK for the trunk as well as the affected release branches.