Re: Bug (or mis-feature) in g77 sequential file format

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

>  I have come accross a problem with the way g77 treats
>  sequential binary files on the alpha. My version is:

>  GNU F77 version egcs-2.91.57 19980901 (egcs-1.1 release)
>  (alpha-dec-osf4.0) compiled by GNU C version egcs-2.91.57
>  19980901 (egcs-1.1 release).  GNU Fortran Front End
>  version 0.5.24-19980804

>  It turns out that this version of g77 for the alpha uses
>  8 bytes for the record's header and trailer (which hold
>  the record length), while the very same g77 version on
>  my PC running FreeBSD uses 4 bytes. The standard DEC
>  Fortran compiler also uses 4-byte headers and trailers.
>  This means that I cannot share binary files.

Excellent summary of the "problem".  We realised this ourselves in  
February.  Basically, the options are:

1. Change the Alpha (and other architectures where `long' means
   64 bits) to use `int' (32 bit) sized integers to count the
   number of bytes in a record.
   This would mean an incompatibility with previous releases of
   egcs on those architectures.

2. Change all architectures to use 64 bit record lengths - this
   would mean to break backwards compatibility for *those*
   architectures.

And then, it wouldn't help.  Most workstations use 32 bit integers  
for the lengths of records in unformatted sequential files, but the  
majority (in number of architectures) is big-endian, whereas the  
Intel and Alpha architectures are little-endian - so you couldn't  
transfer unformatted files between them anyhow.

The real solution is to switch to a file format that's portable  
(i.e. "formatted" files) or write conversion routines.

HTH,
Toon.