https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107565
--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by David Malcolm <dmalc...@gcc.gnu.org>: https://gcc.gnu.org/g:24ebc5404b88b765221b551dc5288f6d64ba3dc7 commit r13-6398-g24ebc5404b88b765221b551dc5288f6d64ba3dc7 Author: David Malcolm <dmalc...@redhat.com> Date: Wed Mar 1 17:24:32 2023 -0500 analyzer: fixes to side-effects for built-in functions [PR107565] Previously, if the analyzer saw a call to a non-pure and non-const built-in function that it didn't have explicit knowledge of the behavior of, it would fall back to assuming that the builtin could have arbitrary behavior, similar to a function defined outside of the current TU. However, this only worked for BUILTIN_NORMAL functions that matched gimple_builtin_call_types_compatible_p; for BUILT_IN_FRONTEND and BUILT_IN_MD, and for mismatched types the analyzer would erroneously assume that the builtin had no side-effects, leading e.g. to PR analyzer/107565, where the analyzer falsely reported that x was still uninitialized after this target-specific builtin: _1 = __builtin_ia32_rdrand64_step (&x); This patch generalizes the handling to cover all classes of builtin, fixing the above false positive. Unfortunately this patch regresses gcc.dg/analyzer/pr99716-1.c due to the: fprintf (fp, "hello"); being optimized to: __builtin_fwrite ("hello", 1, (ssizetype)5, fp_6); and the latter has gimple_builtin_call_types_compatible_p return false, whereas the original call had it return true. I'm assuming that this is an optimization bug, and have filed it as PR middle-end/108988. The effect on the analyzer is that it fails to recognize the call to __builtin_fwrite and instead assumes arbitraty side-effects (including that it could call fclose on fp, hence the report about the leak goes away). I tried various more involved fixes with new heuristics for handling built-ins that aren't explicitly covered by the analyzer, but those fixes tended to introduce many more regressions, so I'm going with this simpler fix. gcc/analyzer/ChangeLog: PR analyzer/107565 * region-model.cc (region_model::on_call_pre): Flatten logic by returning early. Consolidate logic for detecting const and pure functions. When considering whether an unhandled built-in function has side-effects, consider all kinds of builtin, rather than just BUILT_IN_NORMAL, and don't require gimple_builtin_call_types_compatible_p. gcc/testsuite/ChangeLog: PR analyzer/107565 * gcc.dg/analyzer/builtins-pr107565.c: New test. * gcc.dg/analyzer/pr99716-1.c (test_2): Mark the leak as xfailing. Signed-off-by: David Malcolm <dmalc...@redhat.com>
