Re: front end interface

[Nigel Stephens <nigel@algor.co.uk>]

John Carr (jfc@MIT.EDU) writes:
 > > If I understand this correctly, you're depending on memcpy() being
 > > named 'memcpy' ?!
 > > 
 > > This leads into trouble with the current openVMS ports (vax and
 > > alpha), where most library functions are '#define'd with a DECC$ in
 > > front (and others have a __asm() appended to their declaration). So
 > > the compiler doesn't see memcpy but DECC$MEMCPY.
 > 
 > memcpy is recognized by the C front end, as are some of the other
 > string and math functions.

Perhaps a better way to do this in general would be to extend the
__attribute__ mechanism to allow a header file to tell the compiler
more about the behaviour of functions.  For example, since the
"malloc" test is used to tell the "alias" pass that pointers returned
by these functions won't alias to other pointers, we could perhaps
have:

	void * malloc (size_t) __attribute__ ((noalias));

This might then be useful for other functions with similar properties
to malloc(), realloc(), etc.

A similar trick would work for setjmp:

	int setjmp (jmp_buf) __attribute__ ((returns-twice));

As for the builtin use of memcpy() for structure copies etc,
presumably the name of the byte-copy function should be configurable
in the target's header file rather than hardwired into optabs.c.


-- 
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Nigel Stephens, Algorithmics Ltd, 3 Drayton Park, London N5 1NU. England
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