[m-dev.] diff: add type cast to argument of MR_body()

[David Overton]

Estimated hours taken: 1

runtime/mercury_tags.h:
	In the definition of MR_body(), cast the first argument to
	type Word before doing the tag subtraction.
	This is necessary for code such as:
	r3 = MR_const_field(MR_mktag(1), MR_mkword(MR_mktag(1),
		&mercury_const_46), (Integer) 0);
	(which is produced by value numbering).  MR_mkword casts its
	result to type (Word *) which means that MR_body, called from
	within MR_const_field, was doing pointer arithmetic on it and
	thus failing to remove the tag properly.

Index: mercury_tags.h
===================================================================
RCS file: /home/mercury1/repository/mercury/runtime/mercury_tags.h,v
retrieving revision 1.5
diff -u -r1.5 mercury_tags.h
--- mercury_tags.h	1999/04/30 04:25:42	1.5
+++ mercury_tags.h	1999/07/13 02:18:49
@@ -50,7 +50,7 @@
 #define	MR_tag(w)	((w) & ((1 << TAGBITS) - 1))
 #define	MR_mkbody(i)	((i) << TAGBITS)
 #define	MR_unmkbody(w)	((Word) (w) >> TAGBITS)
-#define	MR_body(w, t)	((w) - (t))
+#define	MR_body(w, t)	((Word) (w) - (t))
 #define	MR_strip_tag(w)	((w) & (~(Word)0 << TAGBITS))
 
 #endif /* ! HIGHTAGS */
-- 
David Overton       Department of Computer Science & Software Engineering
MEngSc Student      The University of Melbourne, Australia
+61 3 9344 9159     http://www.cs.mu.oz.au/~dmo
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