https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107582
--- Comment #6 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:a7aef0a5a2b7e20048275a29bd80674c1a061a24 commit r13-4158-ga7aef0a5a2b7e20048275a29bd80674c1a061a24 Author: David Malcolm <dmalc...@redhat.com> Date: Fri Nov 18 19:38:25 2022 -0500 analyzer: fix feasibility false +ve on jumps through function ptrs [PR107582] PR analyzer/107582 reports a false +ve from -Wanalyzer-use-of-uninitialized-value where the analyzer's feasibility checker erroneously decides that point (B) in the code below is reachable, with "x" being uninitialized there: pthread_cleanup_push(func, NULL); while (ret != ETIMEDOUT) ret = rand() % 1000; /* (A): after the while loop */ if (ret != ETIMEDOUT) x = &z; pthread_cleanup_pop(1); if (ret == ETIMEDOUT) return 0; /* (B): after not bailing out */ due to these contradictionary conditions somehow both holding: * (ret == ETIMEDOUT), at (A) (skipping the initialization of x), and * (ret != ETIMEDOUT), at (B) The root cause is that after the while loop, state merger puts ret in the exploded graph in an UNKNOWN state, and saves the diagnostic at (B). Later, as we explore the feasibilty of reaching the enode for (B), dynamic_call_info_t::update_model is called to push/pop the frames for handling the call to "func" in pthread_cleanup_pop. The "ret" at these nodes in the feasible_graph has a conjured_svalue for "ret", and a constraint on it being either == *or* != ETIMEDOUT. However dynamic_call_info_t::update_model blithely clobbers the model with a copy from the exploded_graph, in which "ret" is UNKNOWN. This patch fixes dynamic_call_info_t::update_model so that it simulates pushing/popping a frame on the model we're working with, preserving knowledge of the constraint on "ret", and enabling the analyzer to "know" that the bail-out must happen. Doing so fixes the false positive. gcc/analyzer/ChangeLog: PR analyzer/107582 * engine.cc (dynamic_call_info_t::update_model): Update the model by pushing or pop a frame, rather than by clobbering it with the model from the exploded_node's state. gcc/testsuite/ChangeLog: PR analyzer/107582 * gcc.dg/analyzer/feasibility-4.c: New test. * gcc.dg/analyzer/feasibility-pr107582-1.c: New test. * gcc.dg/analyzer/feasibility-pr107582-2.c: New test. Signed-off-by: David Malcolm <dmalc...@redhat.com>
