gfortran, ncar and blockdata_test failures

[Jack Howarth]

Walter,
    Could you open up a PR for this problem with your testcases
and observations? I would think a decent argument could be made
for it being a regression from g77.
                Jack

On Sat, Nov 17, 2007 at 06:09:25AM -0800, Walter Spector wrote:
> Jack Howarth wrote:
> >     Has anyone looked@the blockdata_test suite that the NCL/NCAR
> > developers have posted...
> > 
> > http://www.ncl.ucar.edu/Download/build_from_src.shtml#CompilersNeeded
> > 
> > I find on powerpc-apple-darwin9 that both gcc 4.2.2 and the current
> > gcc 4.3 snapshots fail this test....
> 
> Ah - the old "put block data in a library, and use EXTERNAL to make sure
> it gets linked in" trick.  Many compilers have gotten this wrong over
> the years, because it is kinda on the edge of being required by the
> Standard (any of them).
> 
> On my cygwin system, g77 and g95 get it right and gfortran gets it wrong.
> See below.
> 
> While F90 modules fixed this problem by obsoleting BLOCK DATA and
> COMMON, quite a number of older library packages depend on this working.
> 
> Walter
> 
> 
> $ cat testsub.f
>       SUBROUTINE TESTSUB
>       EXTERNAL BDTEST
>       COMMON/TEST/WK
>       INTEGER WK
>       PRINT *,'TESTSUB: WK = ',WK, '...it should be 20'
>       RETURN
>       END
> 
> $ g77 -c testsub.f
> $ nm testsub.o
> 00000000 b .bss
> 00000000 d .data
> 00000000 r .rdata
> 00000000 t .text
> 00000004 d ___g77_cilist_0.1
> 00000000 d ___g77_forceload_0.0
>          U _bdtest_               <<<< This references the BLOCK DATA
>          U _do_lio
>          U _e_wsle
>          U _s_wsle
> 00000010 C _test_
> 00000000 T _testsub_
> 
> $ gfortran -c testsub.f
> $ nm testsub.o
> 00000000 b .bss
> 00000000 d .data
> 00000000 r .rdata
> 00000000 t .text                 <<<< Missing a reference to _bdtest_ here
>          U __gfortran_st_write
>          U __gfortran_st_write_done
>          U __gfortran_transfer_character
>          U __gfortran_transfer_integer
> 00000010 C _test_
> 00000000 T _testsub_
> 
> $