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From: "geoffreydgr at icloud dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug analyzer/108100] New: GCC Static Analyzer does not know "(a || b) == true" in the true branch of "if (a || b) " Date: Wed, 14 Dec 2022 12:16:51 +0000 [thread overview] Message-ID: <bug-108100-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108100 Bug ID: 108100 Summary: GCC Static Analyzer does not know "(a || b) == true" in the true branch of "if (a || b) " Product: gcc Version: 13.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: analyzer Assignee: dmalcolm at gcc dot gnu.org Reporter: geoffreydgr at icloud dot com Target Milestone: --- I found a problem that GCC static analyzer does not know "(a||b) == true" in the true branch of "if (a || b) ",and takes the 'true' branch of `if (!a)` and the 'true' branch of `if (!b)` at the same time (which is contradictory), resulting in the wrong report of NPD warning. I think GCC Static Analyer may not handle '||' operator well. Please take a look. I run gcc (trunk) with options `-fanalyzer -O0` https://godbolt.org/z/4Y41j1GfW Input: ```c #include <stdbool.h> int foo(bool a, bool b) { int *c = 0; int *d = 0; if (a || b){ __analyzer_eval(a); __analyzer_eval(b); __analyzer_eval(a||b); __analyzer_eval((a||b) == true); if (!a){ if (!b){ __analyzer_eval(a||b); *d = 0; } } } } ``` Output: ```bash <source>: In function 'foo': <source>:7:9: warning: implicit declaration of function '__analyzer_eval' [-Wimplicit-function-declaration] 7 | __analyzer_eval(a); | ^~~~~~~~~~~~~~~ <source>:7:9: warning: UNKNOWN 7 | __analyzer_eval(a); | ^~~~~~~~~~~~~~~~~~ <source>:8:9: warning: UNKNOWN 8 | __analyzer_eval(b); | ^~~~~~~~~~~~~~~~~~ <source>:9:9: warning: UNKNOWN 9 | __analyzer_eval(a||b); | ^~~~~~~~~~~~~~~~~~~~~ <source>:10:9: warning: UNKNOWN 10 | __analyzer_eval((a||b) == true); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ <source>:14:17: warning: UNKNOWN 14 | __analyzer_eval(a||b); | ^~~~~~~~~~~~~~~~~~~~~ <source>:15:20: warning: dereference of NULL 'd' [CWE-476] [-Wanalyzer-null-dereference] 15 | *d = 0; | ~~~^~~ 'foo': events 1-7 | | 4 | int *c = 0; | | ^ | | | | | (1) 'c' is NULL | 5 | int *d = 0; | | ~ | | | | | (2) 'c' is NULL |...... | 12 | if (!a){ | | ~ | | | | | (3) following 'true' branch... | 13 | if (!b){ | | ~~~ | | || | | |(4) ...to here | | (5) following 'true' branch... | 14 | __analyzer_eval(a||b); | | ~~~~~~~~~~~~~~~~~~~~~ | | | | | (6) ...to here | 15 | *d = 0; | | ~~~~~~ | | | | | (7) dereference of NULL 'd' | Compiler returned: 0 ```
next reply other threads:[~2022-12-14 12:16 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-12-14 12:16 geoffreydgr at icloud dot com [this message] 2023-04-04 1:20 ` [Bug analyzer/108100] " geoffreydgr at icloud dot com
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