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From: "dmalcolm at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug analyzer/104576] New: False positive from
 -Wanalyzer-use-of-uninitialized-value from PR 63311
Date: Wed, 16 Feb 2022 22:47:33 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104576

            Bug ID: 104576
           Summary: False positive from
                    -Wanalyzer-use-of-uninitialized-value from PR 63311
           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: ---

The reproducers for PR 63311, both Fortran and C (attachment 33852) current=
ly
generate false positives from -Wanalyzer-use-of-uninitialized-value when
optimization is off (and they are silent when optimization is on).

It seems to be an issue with -fanalyzer thinking that __builtin_sinf could
clobber *flag (which presumably it can't, being pure or const), thus allowi=
ng
for the "flag is false" branch to skip initialization of t and tt, and then
later executing the "flag is true" branch.=