Bonjour Francois,

Friday, February 07 1997, Francois Thunus wrote to All:

 FT> I have a piece of code here where the ONLY difference between a working
 FT> version and a non working version is a write(''); The non working version
 FT> just freezes (past the write(''), by the way).

Ah, 'deja vue'. I had similar experiences in the early eighties under
Harris' Vulcan OS, using Fortran 77 code. By adding a line like:

        write(6,6000) P
6001    format("The value of P is:", 1PE11.4)

the application was running, without it, it crashed. The reason for this
behaviour was that the format statement occupies some space in memory,
adjacent to a particular array. When i exceeded the bounds of that array,
the format statement acted as a kind of extra buffer, which prevented code
or data being overwritten.

====================
Array WSP

10000 elements
====================
Format statement(s)

====================

I 'discovered' this fact when format statements were mangled by exceeding
array bounds, leading to messages like 'Illegal format for type integer'.
Similar behaviour was displayed by early versions of Ryan-Mcfarlands
Fortran compiler.

 FT> PS this only happens in the Dos (BP 7.01) version, not in the OS/2
 FT> version (either VP 1.03b or Speed 1.51).

That is strange, it must be a case of minor exceedance of the bounds of
your array. It is not a major access violation, otherwise a SIGSEGV should
be generated, as was told me earlier this month.


73 es cuagn,
 Henk

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