Re: Fortran weirdness

[Toon Moene <toon at moene dot indiv dot nluug dot nl>]

Peter Stuge wrote:

> We're in the process of migrating a few different platforms to Linux, one of
> these platforms is Solaris, where we're currently running:
>
> f77: WorkShop Compilers 5.0 98/12/15 FORTRAN 77 5.0
>
> to compile 72k+112k lines of "legacy" (third-party) fortran code into object
> files that are linked with in-house C code.  These binaries run fine.
>
>
> On Linux, using g77 0.5.25 20010319 (prerelease) or 0.5.26 20020220 (release)
> and gcc 2.95.4 20011002 (Debian prerelase), they don't.
>
> Compilation goes fairly well, g77 just tells us this for one of the files:
> --8<--
>          DATA OPTLIS /SIZEOP * ENDLLI/
>                       ^
> Initialization of large (322350-unit) aggregate area `optlis' at (^)
> currently very slow and takes lots of memory during g77 compile -- to be
> improved in 0.6
> -->8--
> but this seems to be a matter of compilation time rather than actual errors
> during compilation.
Yes, this is harmless ...

> Unfortunately, when the program is run, we get into trouble.  The Fortran
> code reads a couple of flatfile databases, using formatted READ()s in all
> the right places, and our g77 compiled code on Linux ends up with NAN in a
> certain position in an array where f77 compiled code on Solaris has 1006.83.
>
> There are a bunch of other, just fine, values before our missing one that
> very likely also originate from the textfile databases.
>
> Any ideas as to why the g77 compiled code ends up with bad data?  Any more
> information I can provide?
>
> I've tried adding -fno-automatic -finit-local-zero -Wpedantic -Wsurprising
> but all this gives is warnings about precedence for immediate negative
> numbers and the gobs of unused variables in the code.  No difference at
> runtime.
Hmmm, you might want to try -Wuninitialized (on its own, combined with 
an optimisation level, because this analysis is only done when 
optimizing), i.e. g77 -O2 -Wuninitialized blah.f.

This might catch variables that are not initialised before use.

Another line of attack might be to compile with array bound checking on 
(the -fbounds-check option).  This tells you when the program tries to 
access arrays outside their declared bounds.

Please inform me of the results of the tests I indicated above; perhaps 
I can help further if this doesn't help.

Cheers,

--
Toon Moene - mailto:toon@moene.indiv.nluug.nl - phoneto: +31 346 214290
Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands
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