On 9/27/19 1:06 PM, Martin Sebor wrote: > GCC declares bcmp, bcopy, and bzero without the nonnull attribute. > This was a deliberate decision as is reflected in the comment in > builtins.def: > > /* bcmp, bcopy and bzero have traditionally accepted NULL pointers > when the length parameter is zero, so don't apply attribute > "nonnull". */ > > But the SUSv3, Issue 6 marks the functions as legacy and recommends > portable applications to replace calls to the functions with the C > standard equivalents as follows: > > #define bcmp(b1,b2,len) memcmp((b1), (b2), (size_t)(len)) > > (The legacy functions have been removed from POSIX in Issue 7.) > > The C standard functions do require their arguments to be nonnull. > > Some libcs (e.g., Glibc) implement the legacy functions in terms > of the C standard equivalents. Others (e.g., libiberty) rely on > strictly undefined behavior in their implementation of these > function (null pointer arithmetic). > > Finally, GCC has been transforming calls to the legacy functions > to the C standard equivalents for a few releases, and making > the same assumptions about their arguments (i.e., eliminating > tests for their pointer arguments being null subsequent to > the calls). > > To help detect some of the same mistakes in calls to the legacy > functions as in the standard ones the attached adds the nonnull > attribute to all three of them. > > Tested on x86_64-linux. Compiling Binutils/GDB and Glibc with > the patch doesn't turn up any -Wnonnull instances. > > Martin > > gcc-80936.diff > > PR tree-optimization/80936 - bcmp, bcopy, and bzero not declared nonnull > > gcc/testsuite/ChangeLog: > > PR tree-optimization/80936 > * gcc.dg/Wnonnull-2.c: New test. > * gcc.dg/Wnonnull-3.c: New test. > * gcc.dg/nonnull-3.c: Expect more warnings. > > gcc/ChangeLog: > > PR tree-optimization/80936 > * builtins.def (bcmp, bcopy, bzero): Declare nonnull. OK. I'll be doing another Fedora rebuild relatively soon, so we'll have a chance to see if there's fallout on a wider codebase. I don't expect significant issues.
jeff
