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* [Bug analyzer/113329] New: analyzer: False positive analyzer-fd-use-without-check with dup2() @ 2024-01-11 8:33 buczek at molgen dot mpg.de 2024-04-28 18:56 ` [Bug analyzer/113329] " alan.coopersmith at oracle dot com 2024-04-28 18:56 ` alan.coopersmith at oracle dot com 0 siblings, 2 replies; 3+ messages in thread From: buczek at molgen dot mpg.de @ 2024-01-11 8:33 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113329 Bug ID: 113329 Summary: analyzer: False positive analyzer-fd-use-without-check with dup2() Product: gcc Version: 14.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: analyzer Assignee: dmalcolm at gcc dot gnu.org Reporter: buczek at molgen dot mpg.de Target Milestone: --- Using a closed file descriptor as the second argument of dup2() is a valid usage. It makes sense, because the implicit close of dup2() doesn't return close errors to the caller, so an explicit close might be preferred. ** Code: #include <unistd.h> void f(int oldfd, int newfd) { close(newfd); dup2(oldfd, newfd); } ** Result: <source>: In function 'f': <source>:4:5: warning: 'dup2' on possibly invalid file descriptor 'newfd' [-Wanalyzer-fd-use-without-check] 4 | dup2(oldfd, newfd); | ^~~~~~~~~~~~~~~~~~ 'f': events 1-2 | | 3 | close(newfd); | | ^~~~~~~~~~~~ | | | | | (1) closed here | 4 | dup2(oldfd, newfd); | | ~~~~~~~~~~~~~~~~~~ | | | | | (2) 'newfd' could be invalid | Compiler returned: 0 https://gcc.godbolt.org/z/8zac19e15 ^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug analyzer/113329] analyzer: False positive analyzer-fd-use-without-check with dup2() 2024-01-11 8:33 [Bug analyzer/113329] New: analyzer: False positive analyzer-fd-use-without-check with dup2() buczek at molgen dot mpg.de @ 2024-04-28 18:56 ` alan.coopersmith at oracle dot com 2024-04-28 18:56 ` alan.coopersmith at oracle dot com 1 sibling, 0 replies; 3+ messages in thread From: alan.coopersmith at oracle dot com @ 2024-04-28 18:56 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113329 Alan Coopersmith <alan.coopersmith at oracle dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |alan.coopersmith at oracle dot com --- Comment #1 from Alan Coopersmith <alan.coopersmith at oracle dot com> --- Created attachment 58057 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58057&action=edit dup2.c test case ^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug analyzer/113329] analyzer: False positive analyzer-fd-use-without-check with dup2() 2024-01-11 8:33 [Bug analyzer/113329] New: analyzer: False positive analyzer-fd-use-without-check with dup2() buczek at molgen dot mpg.de 2024-04-28 18:56 ` [Bug analyzer/113329] " alan.coopersmith at oracle dot com @ 2024-04-28 18:56 ` alan.coopersmith at oracle dot com 1 sibling, 0 replies; 3+ messages in thread From: alan.coopersmith at oracle dot com @ 2024-04-28 18:56 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113329 --- Comment #2 from Alan Coopersmith <alan.coopersmith at oracle dot com> --- I've hit this as well with gcc 13.2 when building xfs with -fanalyzer. I extracted this test case from https://gitlab.freedesktop.org/xorg/app/xfs/-/blob/master/os/daemon.c and when built with "gcc -fanalyzer -c dup2.c" it reports: dup2.c: In function ‘DetachStdio’: dup2.c:23:13: warning: ‘dup2’ on possibly invalid file descriptor ‘0’ [-Wanalyzer-fd-use-without-check] 23 | if (dup2(nullfd, 0) == -1) { | ^~~~~~~~~~~~~~~ ‘DetachStdio’: events 1-6 | | 10 | close (0); | | ^~~~~~~~~ | | | | | (1) closed here |...... | 18 | if (nullfd == -1) { | | ~ | | | | | (2) following ‘false’ branch (when ‘nullfd != -1’)... |...... | 22 | if (nullfd != 0) { | | ~ | | | | | (3) ...to here | | (4) following ‘true’ branch (when ‘nullfd != 0’)... | 23 | if (dup2(nullfd, 0) == -1) { | | ~~~~~~~~~~~~~~~ | | | | | (5) ...to here | | (6) ‘0’ could be invalid | ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2024-04-28 18:56 UTC | newest] Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2024-01-11 8:33 [Bug analyzer/113329] New: analyzer: False positive analyzer-fd-use-without-check with dup2() buczek at molgen dot mpg.de 2024-04-28 18:56 ` [Bug analyzer/113329] " alan.coopersmith at oracle dot com 2024-04-28 18:56 ` alan.coopersmith at oracle dot com
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