[Bug 1717433] [NEW] Spurious warning: ‘r’ may be used uninitialized in this function [-Wmaybe-uninitialized]

[Daniel van Vugt]

Public bug reported:

gcc is giving an apparently spurious warning:

shadow.c: In function ‘create_shadowed_pixbuf’:
shadow.c:16:28: warning: ‘r’ may be used uninitialized in this function [-Wmaybe-uninitialized]
     return ((1 / (2 * M_PI * r)) *
                  ~~~~~~~~~~^~~~
shadow.c:14:1: note: ‘r’ was declared here
 gaussian (double x, double y, double r)
 ^~~~~~~~

It looks like that's impossible to me. The relevant source file is:

https://git.gnome.org/browse/gtk+/tree/docs/tools/shadow.c?h=gtk-3-22

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: gcc-7 7.2.0-3ubuntu1
ProcVersionSignature: Ubuntu 4.12.0-13.14-generic 4.12.10
Uname: Linux 4.12.0-13-generic x86_64
ApportVersion: 2.20.7-0ubuntu1
Architecture: amd64
Date: Fri Sep 15 14:06:45 2017
InstallationDate: Installed on 2017-05-03 (135 days ago)
InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Alpha amd64 (20170502)
SourcePackage: gcc-7
UpgradeStatus: No upgrade log present (probably fresh install)

** Affects: gcc-7 (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug artful

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https://bugs.launchpad.net/bugs/1717433

Title:
  Spurious warning: ‘r’ may be used uninitialized in this function
  [-Wmaybe-uninitialized]

Status in gcc-7 package in Ubuntu:
  New

Bug description:
  gcc is giving an apparently spurious warning:

  shadow.c: In function ‘create_shadowed_pixbuf’:
  shadow.c:16:28: warning: ‘r’ may be used uninitialized in this function [-Wmaybe-uninitialized]
       return ((1 / (2 * M_PI * r)) *
                    ~~~~~~~~~~^~~~
  shadow.c:14:1: note: ‘r’ was declared here
   gaussian (double x, double y, double r)
   ^~~~~~~~

  It looks like that's impossible to me. The relevant source file is:

  https://git.gnome.org/browse/gtk+/tree/docs/tools/shadow.c?h=gtk-3-22

  ProblemType: Bug
  DistroRelease: Ubuntu 17.10
  Package: gcc-7 7.2.0-3ubuntu1
  ProcVersionSignature: Ubuntu 4.12.0-13.14-generic 4.12.10
  Uname: Linux 4.12.0-13-generic x86_64
  ApportVersion: 2.20.7-0ubuntu1
  Architecture: amd64
  Date: Fri Sep 15 14:06:45 2017
  InstallationDate: Installed on 2017-05-03 (135 days ago)
  InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Alpha amd64 (20170502)
  SourcePackage: gcc-7
  UpgradeStatus: No upgrade log present (probably fresh install)

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