https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104434
--- Comment #4 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:aee1adf2cdc1cf4e116e5c05b6e7c92b0fbb264b commit r12-7364-gaee1adf2cdc1cf4e116e5c05b6e7c92b0fbb264b Author: David Malcolm <dmalc...@redhat.com> Date: Wed Feb 23 09:14:58 2022 -0500 analyzer: handle __attribute__((const)) [PR104434] When testing -fanalyzer on openblas-0.3, I noticed slightly over 2000 false positives from -Wanalyzer-malloc-leak on code like this: if( LAPACKE_lsame( vect, 'b' ) || LAPACKE_lsame( vect, 'p' ) ) { pt_t = (lapack_complex_float*) LAPACKE_malloc( sizeof(lapack_complex_float) * ldpt_t * MAX(1,n) ); [...snip...] } [...snip lots of code...] if( LAPACKE_lsame( vect, 'b' ) || LAPACKE_lsame( vect, 'q' ) ) { LAPACKE_free( pt_t ); } where LAPACKE_lsame is a char-comparison function implemented in a different TU. The analyzer naively considers the execution path where: LAPACKE_lsame( vect, 'b' ) || LAPACKE_lsame( vect, 'p' ) is true at the malloc guard, but then false at the free guard, which is thus a memory leak. This patch makes -fanalyer respect __attribute__((const)), so that the analyzer treats such functions as returning the same value when given the same inputs. I've filed https://github.com/xianyi/OpenBLAS/issues/3543 suggesting that LAPACKE_lsame be annotated with __attribute__((const)); with that, and with this patch, the false positives seem to be fixed. gcc/analyzer/ChangeLog: PR analyzer/104434 * analyzer.h (class const_fn_result_svalue): New decl. * region-model-impl-calls.cc (call_details::get_manager): New. * region-model-manager.cc (region_model_manager::get_or_create_const_fn_result_svalue): New. (region_model_manager::log_stats): Log m_const_fn_result_values_map. * region-model.cc (const_fn_p): New. (maybe_get_const_fn_result): New. (region_model::on_call_pre): Handle fndecls with __attribute__((const)) by calling the above rather than making a conjured_svalue. * region-model.h (visitor::visit_const_fn_result_svalue): New. (region_model_manager::get_or_create_const_fn_result_svalue): New decl. (region_model_manager::const_fn_result_values_map_t): New typedef. (region_model_manager::m_const_fn_result_values_map): New field. (call_details::get_manager): New decl. * svalue.cc (svalue::cmp_ptr): Handle SK_CONST_FN_RESULT. (const_fn_result_svalue::dump_to_pp): New. (const_fn_result_svalue::dump_input): New. (const_fn_result_svalue::accept): New. * svalue.h (enum svalue_kind): Add SK_CONST_FN_RESULT. (svalue::dyn_cast_const_fn_result_svalue): New. (class const_fn_result_svalue): New. (is_a_helper <const const_fn_result_svalue *>::test): New. (template <> struct default_hash_traits<const_fn_result_svalue::key_t>): New. gcc/testsuite/ChangeLog: PR analyzer/104434 * gcc.dg/analyzer/attr-const-1.c: New test. * gcc.dg/analyzer/attr-const-2.c: New test. * gcc.dg/analyzer/attr-const-3.c: New test. * gcc.dg/analyzer/pr104434-const.c: New test. * gcc.dg/analyzer/pr104434-nonconst.c: New test. * gcc.dg/analyzer/pr104434.h: New test. Signed-off-by: David Malcolm <dmalc...@redhat.com>
