Code generation bug in Microsoft C 5.1

[Christian Franke]

Code generation bug in Microsoft C 5.1 (MS-DOS, OS/2)
======================================

If an unsigned char variable is {pre|post}incremented inside an array subscript,
the compiler generates code to increment a *word*. The error does not
occur if the variable is signed.

Example

	char c;
	unsigned char uc;
	char a[10];

	error()
	{
	    char i;
		i = uc++;    /* OK */
		i = a[c++];  /* OK */
		i = a[uc++]; /* Error */
	}

Code generated

	;****** i = a[uc++];
		mov bl,BYTE PTR _uc
		inc WORD PTR _uc	*WOW*
		sub bh,bh
		mov al,BYTE PTR _a[bx]
		mov BYTE PTR [bp-2],al


This error does not occur with MSC version 4.0.


Christian Franke

	Aachen University of Technology
	Lehrstuhl fuer Informatik I
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