$ 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
