[Bug fortran/18794] New: warn about common variable alignment problems

[Thomas dot Koenig at online dot de]

$ cat common.f
      program main
      character*1 c
      common /foo/ c,r
      c = 'a'
      r = 1.2
      end
$ g77 common.f
common.f: In program `main':
common.f:3: warning:
         common /foo/ c,r
                 ^
Initial padding for common block `foo' is 3 bytes at (^) -- consider
reorderingmembers, largest-type-size first
$ gfortran common.f
$ gfortran -v
Reading specs from /home/ig25/lib/gcc/i686-pc-linux-gnu/4.0.0/specs
Configured with: ../gcc/configure --prefix=/home/ig25
--enable-languages=c,c++,f95 : (reconfigured) ../gcc/configure
--prefix=/home/ig25 --with-gcc-version-trigger=/home/ig25/gcc/gcc/version.c
--enable-languages=c,c++,f95 --no-create --no-recursion
Thread model: posix
gcc version 4.0.0 20041129 (experimental)

Just about any Fortran compiler warns about this sort
of thing (and they should, the performance penalty
for this kind of thing can be severe).

-- 
           Summary: warn about common variable alignment problems
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: Thomas dot Koenig at online dot de
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18794