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From: "1zeeky at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/98871] New: Cannot silence -Wmaybe-uninitialized at declaration site Date: Thu, 28 Jan 2021 21:44:34 +0000 [thread overview] Message-ID: <bug-98871-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98871 Bug ID: 98871 Summary: Cannot silence -Wmaybe-uninitialized at declaration site Product: gcc Version: 11.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: 1zeeky at gmail dot com Target Milestone: --- Created attachment 50077 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50077&action=edit testcase I have some code where I'm relying on the caller to uphold some guarantee in order to properly initialize a variable. gcc correctly detects that the variable maybe left uninitialized. The warning is correct, but I am unable to properly silence this warning because the warning doesn't "show up" at the location where the variable is declared, but where it is used, which is another function, which receives it via pointer. This is probably better explained with the testcase. The setup is a bit weird and looks like it could be minimized. I needed to increase the complexity to thwart static analysis sufficiently such that gcc is unsure if 'max' gets initialized or not. Here's the warning I get: $ gcc -O -Wmaybe-uninitialized maybe-uninit.c maybe-uninit.c: In function ‘main’: maybe-uninit.c:8:9: warning: ‘max.x’ may be used uninitialized in this function [-Wmaybe-uninitialized] 8 | return ++*x; | ^~~~ maybe-uninit.c:15:13: note: ‘max.x’ was declared here 15 | struct Foo max; | ^~~ A site-note: the first line in the error-report states "In function ‘main’" for some reason. I would like to silence the warning from within foo() (my failed attempt at using '#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"' is left in the testcase), since inc() is used in other places where having this warning may be beneficial. The warning would probably have to change to something like maybe-uninit.c: In function ‘foo’: maybe-uninit.c:22:13: warning: 'max.x' is passed to function 'inc', where it may be used uninitialized [-Wmaybe-pass-uninitialized] 22 | return inc(&max.x); | ^~~~~~ maybe-uninit.c:8:9: note: ‘max.x’ used here 8 | return ++*x; | ^~~~ maybe-uninit.c:15:13: note: ‘max.x’ was declared here 15 | struct Foo max; Alternatively, a variable attribute would work for me as well, e.g. '__attribute__((assume_initialized))'. Locally I use gcc 10.2.0, but through godbolt.org I also tested 10.2.1 and "gcc (trunk)" which describes itself as "gcc (Compiler-Explorer-Build) 11.0.0 20210127 (experimental)".
next reply other threads:[~2021-01-28 21:44 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-01-28 21:44 1zeeky at gmail dot com [this message] 2021-01-28 21:46 ` [Bug c/98871] " 1zeeky at gmail dot com 2021-01-29 0:49 ` [Bug middle-end/98871] " msebor at gcc dot gnu.org 2021-01-29 0:59 ` msebor at gcc dot gnu.org 2021-01-29 21:56 ` msebor at gcc dot gnu.org 2021-01-29 21:56 ` msebor at gcc dot gnu.org 2021-06-10 23:31 ` msebor at gcc dot gnu.org 2021-07-02 22:20 ` cvs-commit at gcc dot gnu.org 2021-07-06 19:43 ` cvs-commit at gcc dot gnu.org 2021-11-12 19:44 ` msebor at gcc dot gnu.org
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