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From: berkley@wucs1.wustl.edu (Berkley Shands)
Newsgroups: comp.sys.mips
Subject: Mips Fortran Bugs
Keywords: Fortran, Bugs, MIPS
Message-ID: <938@wucs1.wustl.edu>
Date: 28 Jul 89 14:30:19 GMT
Organization: Washington University, St. Louis, MO
Lines: 39


	In porting a LARGE fortran package to a MIPS based engine,
(the decstation 3100 + the IRIS 4d power series) I ran across the following
nasty bugs...

1)	The compiler (with standard optimization) will optimize away
identical argument lists to subroutine calls WHEN
	The calls follow each other using the EXACT SAME list, and
	the first argument is an array or a character string.

	call foo(a,b,c)
	call zor(a,b,c)

	The "a" argument is stack bound, but the data is trashed. It usually
	is a small fixed constant. The cure is to vary the argument list
	so it is not re-used by the compiler.

2)	END=nn,ERR=NN on READS are really random branch statements.

3)	The format (<var>L2) logical format, variable length, fixed size
fields works on OUTPUT. On Input, that read and all subsequent reads will
return NULLS or EOF.

4)	The compiler is VERY picky about ENTRY statements. All entry
points to a function/subroutine must share the SAME TYPE and ARGUMENT LISTS.

5)	The runtime system (iris 4d this time) can lose file position
on reads if to much I/O is done on consecutive i/o chanels (unit=1,unit=2...)

6)	Passing character strings as arguments when the string is
$INCLUDED and in common will sometimes pass trash or nulls. The larger
the compilation unit, the worse the trouble.

	I hope this helps anyone trying to port VAX fortran to
these noce FAST engines!

	Berkley Shands
	BERKLEY.WUSTL.EDU (BITNET)
	DECUS VAX SIG Exec