Re: Syscall changes registers beyond %eax, on linux-i386

[Richard Henderson]

On Thu, Sep 19, 2002 at 02:51:44PM -0400, Brian Gerst wrote:
> > The parameter area belongs to the callee, and it may *always* be modified.
> 
> The parameters can not be modified if they are declared const though, 
> that's my point.

Yes they can.

	extern void bar(int x, int y, int z);
	void foo(const int a, const int b, const int c)
	{
	  bar(a+1, b+1, c+1);
	}

        subl    $12, %esp
        movl    20(%esp), %eax
        incl    %eax
        movl    %eax, 20(%esp)
        movl    16(%esp), %eax
        incl    %eax
        incl    24(%esp)
        movl    %eax, 16(%esp)
        addl    $12, %esp
        jmp     bar

(Not sure why gcc doesn't use incl on all three memories, nor
should it allocate that stack frame...)

r~