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digitalmars.D.bugs - Problem with asm and short

reply Ary Manzana <Ary_member pathlink.com> writes:
I think this program:

----------------------------
import std.stdio;

void main() {

short* s = new short[3];
s[0] = 1;
s[1] = 2;
s[2] = 3;

int a = 0;

asm {
mov EAX, s;
mov ECX, [EAX];
mov a, ECX;
}

writefln("%s", a);	
}
----------------------------

should output 1, but it outputs 131073 (garbage). However, if instead of [EAX]
you write [EAX + 4] it outputs 3 (and with [EAX + 2] garbage again). Am I doing
something wrong or this is a bug?

If the array is of ints, the programs works OK.
Jun 25 2006
parent Tom S <h3r3tic remove.mat.uni.torun.pl> writes:
Ary Manzana wrote:
 asm {
 mov EAX, s;
 mov ECX, [EAX];
 mov a, ECX;
 }
 
 should output 1, but it outputs 131073 (garbage). However, if instead of [EAX]
 you write [EAX + 4] it outputs 3 (and with [EAX + 2] garbage again). Am I doing
 something wrong or this is a bug?
 
 If the array is of ints, the programs works OK.

Shorts are 16bit, ECX is 32bit. 'mov ECX, [EAX]' copies 32bits from the [EAX] address to ECX, while you should only copy 16 (a short/word). Try this: asm { mov EAX, s; xor ECX, ECX; mov CX, [EAX]; mov a, ECX; } -- Tomasz Stachowiak /+ a.k.a. h3r3tic +/
Jun 25 2006