Hi Erik,
On Monday 02 January 2006 14:53, Erik Hofman wrote:
> # define PUSH(r) do { \
> if(ctx->opTop >= MAX_STACK_DEPTH) ERR(ctx, "stack overflow"); \
> ctx->opStack[ctx->opTop++] = r; \
> } while(0)
[...]
> The only thing I can think of right now is that inside the function the
> code is working with a *copy* of r
>
> I'm puzzled.
I am not sure, but for the first thing, the lines around 427 look suspicious
to me. They also reference opTop from the ctx variable which is modified by
the macro.
I believe that the order of the increment and the assignent of the array is
undefined in this macro expansion.
I beileve that the compiler might be free to interpret the following:
ctx->opStack[ctx->opTop++] = ctx->opStack[ctx->opTop-1];
to either:
int tmpindex = ctx->opTop;
ctx->opStack[tmpindex] = ctx->opStack[ctx->opTop-1];
ctx->opTop++;
or
int tmpindex = ctx->opTop;
ctx->opTop++;
ctx->opStack[tmpindex] = ctx->opStack[ctx->opTop-1];
which is obviously not the same.
Good detective work Erik!
Greetings and happy new year
Mathias
--
Mathias Fröhlich, email: [EMAIL PROTECTED]
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