From:	"A.Appleyard" <A DOT APPLEYARD AT fs2 DOT mt DOT umist DOT ac DOT uk>
Organization:	Materials Science Centre
To:	DJGPP AT DELORIE DOT COM
Date:	Thu, 19 Sep 1996 09:04:06 GMT
Subject:	array-bound-checking
Message-ID:	<17B73660C60@fs2.mt.umist.ac.uk>

  (1) Thankyou for the various helpful replies to my recent admittedly very
off-topic query about Windows programming; I am sorry if I annoyed anyone.

  (2) One thing that I miss in C is optional array-bound-checking like I found
so useful in Algol-like languages and even in primitive `autocodes' for
mainframes long before there were desktop computers; that facility quickly and
easily spotted many out-of-bounds store accesses that in C programs are often
the devil's own job to track down. Is putting an array bound in these C or C++
constructions forbidden, or is it allowed but ignored?:-
    int zxcvbnm(int n,double x[n]) { ...... }
    double *x[n+2];
  If it is allowed, it would provide a way to specify size of parametric and
pointed-to arrays for a possible array-bound-check compiler option.

  (3) It would be useful to have a pragma to tell the compiler to loop-unroll
if possible one particular for or while loop instead of wasting compile time
testing if every such loop in the program is unrollable. E.g.:-
    inline double pow(double x,int n){int i; double y;
    if(n<0) {x=1/x; n=-n;} y=1;
    while/*#unroll*/(n) {if(n&1) y*=x; x=x*x; n>>=1;}
    return y;}
  and e.g. `z=pow(x,4);' would expand and reduce to `EAX=x*x; z=EAX*EAX;'.

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