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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/108704] New: Many
 -Wanalyzer-use-of-uninitialized-value false positives seen in qemu's
 softfloat.c
Date: Tue, 07 Feb 2023 23:13:14 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108704

            Bug ID: 108704
           Summary: Many -Wanalyzer-use-of-uninitialized-value false
                    positives seen in qemu's softfloat.c
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: analyzer
          Assignee: dmalcolm at gcc dot gnu.org
          Reporter: dmalcolm at gcc dot gnu.org
  Target Milestone: ---

Created attachment 54425
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D54425&action=3Dedit
Reduced reproducer

Trunk shows many (dozens?) of -Wanalyzer-use-of-uninitialized-value false
positives on qemu's softfloat.c

https://godbolt.org/z/MTe9597Eh shows:

<source>: In function 'test':
<source>:27:9: warning: use of uninitialized value 'fp0' [CWE-457]
[-Wanalyzer-use-of-uninitialized-value]
   27 |   fp0 =3D floatx80_add(fp0, float32_to_floatx80((0x3F800000)));
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  'test': events 1-3
    |
    |   24 |   floatx80 fp0;
    |      |            ^~~
    |      |            |
    |      |            (1) region created on stack here
    |      |            (2) capacity: 16 bytes
    |......
    |   27 |   fp0 =3D floatx80_add(fp0, float32_to_floatx80((0x3F800000)));
    |      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    |      |         |
    |      |         (3) use of uninitialized value 'fp0' here
    |
Compiler returned: 0

where fp0 appears to have been initialized on the line above.=