Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!ncc!adec23!mark
From: mark@adec23.UUCP (Mark Salyzyn)
Newsgroups: comp.lang.c
Subject: Re: Short code to determine compiler's
Summary: Nope, asking the compiler is not the answer
Message-ID: <1706@adec23.UUCP>
Date: 24 Jul 89 20:26:44 GMT
References: <396@uop.uop.EDU> <225800197@uxe.cso.uiuc.edu> <579@targon.UUCP>
Followup-To: comp.lang.c
Organization: ADEC Systems Inc., Edmonton, Alberta
Lines: 25

In article <579@targon.UUCP>, andre@targon.UUCP (andre) writes:
>Yes, I think you can write a program that checks the nr of registers,
> ...
>main()
>{
>	register n1, n2, n3, n4, n5, n6, n7, n8; /* etc. */
>	int *a;
>	a = &n8;
>	/* repeat n6 - n2 */
>	a = &n1;
>}
>You can take the address of a variable but not of a register.

I have several compilers (Aztec C-80, MSC3.0, SYSV cc) that will complain with
ALL of the address taking and only assign a pair of them to registers. I'm
sorry but this is not the answer. I can't even find in the source code of the
C compiler how many registers are used :-).

As far as runtime is concerned, just do a decrement loop on each of the
register variables and check the time. The non-register variables will
take longer to do the loop (probably???). In my next posting I will
divulge the secrets of the Universe :-) :-).

Ciao,
-- Mark Salyzyn