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From: "dmalcolm at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug analyzer/105962] New: Unhelpful diagnostics paths from analyzer in the face of inlining Date: Mon, 13 Jun 2022 22:11:14 +0000 [thread overview] Message-ID: <bug-105962-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105962 Bug ID: 105962 Summary: Unhelpful diagnostics paths from analyzer in the face of inlining Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: analyzer Assignee: dmalcolm at gcc dot gnu.org Reporter: dmalcolm at gcc dot gnu.org Target Milestone: --- Consider this double-free: void foo (void *p) { __builtin_free (p); } void bar (void *q) { foo (q); foo (q); } Below -O2, -fanalyzer shows the calls and returns: ../../src/gcc/testsuite/gcc.dg/analyzer/inline-1.c: In function ‘foo’: ../../src/gcc/testsuite/gcc.dg/analyzer/inline-1.c:3:3: warning: double-‘free’ of ‘p’ [CWE-415] [-Wanalyzer-double-free] 3 | __builtin_free (p); | ^~~~~~~~~~~~~~~~~~ ‘bar’: events 1-2 | | 6 | void bar (void *q) | | ^~~ | | | | | (1) entry to ‘bar’ | 7 | { | 8 | foo (q); | | ~~~~~~~ | | | | | (2) calling ‘foo’ from ‘bar’ | +--> ‘foo’: events 3-4 | | 1 | void foo (void *p) | | ^~~ | | | | | (3) entry to ‘foo’ | 2 | { | 3 | __builtin_free (p); | | ~~~~~~~~~~~~~~~~~~ | | | | | (4) first ‘free’ here | <------+ | ‘bar’: events 5-6 | | 8 | foo (q); | | ^~~~~~~ | | | | | (5) returning to ‘bar’ from ‘foo’ | 9 | foo (q); | | ~~~~~~~ | | | | | (6) passing freed pointer ‘q’ in call to ‘foo’ from ‘bar’ | +--> ‘foo’: events 7-8 | | 1 | void foo (void *p) | | ^~~ | | | | | (7) entry to ‘foo’ | 2 | { | 3 | __builtin_free (p); | | ~~~~~~~~~~~~~~~~~~ | | | | | (8) second ‘free’ here; first ‘free’ was at (4) | but at -O2 and above, we show the unhelpful: In function ‘foo’, inlined from ‘bar’ at ../../src/gcc/testsuite/gcc.dg/analyzer/inline-1.c:9:3: ../../src/gcc/testsuite/gcc.dg/analyzer/inline-1.c:3:3: warning: double-‘free’ of ‘q’ [CWE-415] [-Wanalyzer-double-free] 3 | __builtin_free (p); | ^~~~~~~~~~~~~~~~~~ ‘bar’: events 1-2 | | 3 | __builtin_free (p); | | ^~~~~~~~~~~~~~~~~~ | | | | | (1) first ‘free’ here | | (2) second ‘free’ here; first ‘free’ was at (1) which is somewhat mystifying. This is happening because -fanalyzer is running after inlining and sees this at the gimple level: void bar (void * q) { <bb 2> [local count: 1073741824]: __builtin_free (q_2(D)); __builtin_free (q_2(D)); return; } We can probably improve the readability by fixing up the events in the diagnostic path based on the LOCATION_BLOCK inlining information captured in the stmt location values. I tried a version of this years ago in: https://dmalcolm.fedorapeople.org/gcc/2020-02-20/gcc-newgit-analyzer-gcc10-analysis-gcc10-v52-relative-to-bc0f8df124f6ee12c82c5a6c1335868a15bcaecb/0012-FIXME-WIP-on-inlining-and-paths.patch
next reply other threads:[~2022-06-13 22:11 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-06-13 22:11 dmalcolm at gcc dot gnu.org [this message] 2022-06-15 13:21 ` [Bug analyzer/105962] " dmalcolm at gcc dot gnu.org 2022-06-15 21:47 ` cvs-commit at gcc dot gnu.org 2022-06-15 22:05 ` dmalcolm at gcc dot gnu.org
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