[Bug c/49617] New: gcc misses uninititialized variables in contained functions

[pault at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49617

           Summary: gcc misses uninititialized variables in contained
                    functions
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: pault@gcc.gnu.org


This was reported to the gfortran list by Bill Paxton:

gfortran test_uninit.f -O2 -Wall -o test; ./test


     module test_mod
     implicit none

     contains

     subroutine test
        integer :: x, y
        call t
        write(*,*) 'y', y

        contains

        subroutine t
        y = x * 5
        end subroutine t

     end subroutine test

     end module test_mod


     program test_uninit
     use test_mod
     implicit none
     call test
     end program test_uninit

No warning is given that 'x' is used uninitialized in subroutine 't'.

The uninitialized checking is done in tree-ssa.c and tree-ssa-uninit.c, so this
should be attributed to gcc.

Tobias Burnus produced this (using gcc extension) testcase in C

int
main (void)
{
 int y;

 int func(void)
 {
   int x;
   /*int z;*/

   x = y;
   /* x = z;*/
   return x;
 }
 return func();
}

This also fails to report on the state of y, when used in 'func'.

I understand that fixing this will not be straightforward but have submitted it
for the record at least.

Paul