https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93993
--- Comment #2 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:e516294a1acb28aaaad44cfd583cc6a80354044e commit r10-7024-ge516294a1acb28aaaad44cfd583cc6a80354044e Author: David Malcolm <dmalc...@redhat.com> Date: Tue Mar 3 16:36:13 2020 -0500 analyzer: handle __builtin_expect [PR93993] The false warning: pr93993.f90:19:0: 19 | allocate (tm) ! { dg-warning "dereference of possibly-NULL" } | Warning: dereference of possibly-NULL ‘_6’ [CWE-690] [-Wanalyzer-possible-null-dereference] in the reproducer for PR analyzer/93993 is due to a BUILTIN_EXPECT in the chain of SSA expressions between the malloc and the condition guarding the edge: the analyzer didn't "know" about the relationship between initial argument to BUILTIN_EXPECT and the return value. This patch implements support for BUILTIN_EXPECT so that the return value is known to be equal to the initial argument. This adds constraints when exploring the CFG edges, eliminating the above false positive. Doing so also eliminated the leak warning from the reproducer. The issue was that leaked_pvs was empty within impl_region_model_context::on_state_leak, due to the leaking region being a view, of type struct Pdtet_8 *, of a region of type struct pdtet_8 *, which led region_model::get_representative_path_var to return a NULL_TREE value. Hence the patch also implements view support for region_model::get_representative_path_var, restoring the leak diagnostic, albeit changing the wording to: Warning: leak of ‘(struct Pdtet_8) qb’ [CWE-401] [-Wanalyzer-malloc-leak] It's not clear to me if we should emit leaks at a fortran "end program" (currently we suppress them for leaks at the end of main). gcc/analyzer/ChangeLog: PR analyzer/93993 * region-model.cc (region_model::on_call_pre): Handle BUILT_IN_EXPECT and its variants. (region_model::add_any_constraints_from_ssa_def_stmt): Split out gassign handling into add_any_constraints_from_gassign; add gcall handling. (region_model::add_any_constraints_from_gassign): New function, based on the above. Add handling for NOP_EXPR. (region_model::add_any_constraints_from_gcall): New function. (region_model::get_representative_path_var): Handle views. * region-model.h (region_model::add_any_constraints_from_ssa_def_stmt): New decl. (region_model::add_any_constraints_from_gassign): New decl. gcc/testsuite/ChangeLog: PR analyzer/93993 * gcc.dg/analyzer/expect-1.c: New test. * gcc.dg/analyzer/malloc-4.c: New test. * gfortran.dg/analyzer/pr93993.f90: Remove xfail from dg-bogus. Move location of leak warning and update message.
