[Bug c++/81714] New: incorrect location for uninitialised variable

["akim.demaille at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81714

            Bug ID: 81714
           Summary: incorrect location for uninitialised variable
           Product: gcc
           Version: 7.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: akim.demaille at gmail dot com
  Target Milestone: ---

Hi,

This seems to be different from #55874 and #60350, but I might be wrong.  The
caret-display makes it particularly visible.  This affects GCC 4.9, 5.4.0,
6.3.0, and 7.1.1.

$ cat /tmp/foo.cc
int main()
{
  int i;
  return i + 42;
}
$ g++-mp-7 -Wall /tmp/foo.cc
/tmp/foo.cc: In function 'int main()':
/tmp/foo.cc:4:14: warning: 'i' is used uninitialized in this function
[-Wuninitialized]
   return i + 42;
              ^~
$ gcc-mp-7 --version
gcc-mp-7 (MacPorts gcc7 7-20170622_0) 7.1.
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ g++-mp-6 -Wall /tmp/foo.cc
/tmp/foo.cc: In function 'int main()':
/tmp/foo.cc:4:14: warning: 'i' is used uninitialized in this function
[-Wuninitialized]
   return i + 42;
              ^~
$ g++-mp-5 -Wall /tmp/foo.cc
/tmp/foo.cc: In function 'int main()':
/tmp/foo.cc:4:14: warning: 'i' is used uninitialized in this function
[-Wuninitialized]
   return i + 42;
              ^
$ g++-mp-4.9 -Wall /tmp/foo.cc
/tmp/foo.cc: In function 'int main()':
/tmp/foo.cc:4:14: warning: 'i' is used uninitialized in this function
[-Wuninitialized]
   return i + 42;
              ^


In C mode, GCC is not affected, but the location is not very accurate either.

$ cat /tmp/foo.c
int main()
{
  int i;
  return i + 42;
}
$ gcc-mp-7 -Wall /tmp/foo.c
/tmp/foo.c: In function 'main':
/tmp/foo.c:4:12: warning: 'i' is used uninitialized in this function
[-Wuninitialized]
   return i + 42;
          ~~^~~~

It seems somewhat specific to this particular warning.


$ cat /tmp/foo.cc
int main()
{
  [[deprecated]]
  int a;
  return 1 + a;
}
$ g++-mp-7 -Wall /tmp/foo.cc -std=c++14
/tmp/foo.cc: In function 'int main()':
/tmp/foo.cc:5:14: warning: 'a' is deprecated [-Wdeprecated-declarations]
   return 1 + a;
              ^
/tmp/foo.cc:4:9: note: declared here
     int a;
         ^
/tmp/foo.cc:5:14: warning: 'a' is used uninitialized in this function
[-Wuninitialized]
   return 1 + a;
              ^



Cheers!