Thibaud GUERIN writes:
> On 4/22/06, Andrew Haley <aph@xxxxxxxxxxx> wrote:
> > Thibaud GUERIN writes:
> > > On 4/21/06, Andrew Haley <aph@xxxxxxxxxxx> wrote:
> > > > Thibaud GUERIN writes:
> > > > > >
> > > >
> > > > OK, so we've got rid of the asms and casting away const, and the code
> > > > still doesn't work.
> > > >
> > > > So, your code is now, at last, legal C. Let's have a look at the
> > > > assembly code generated for my_own_printf (use gcc -S). Be sure to
> > > > include the exact command line you used.
> >
> > > my_own_printf:
> >
> > Args are just below sp.
> >
> > > pushl %ebp
> > > movl %esp, %ebp
> >
> > ebp points to: frame, retaddr, arg0
> >
> > > subl $8, %esp
> > > leal 8(%ebp), %eax
> >
> > eax contains ebp+8: it points to arg0
> >
> > > movl %eax, -4(%ebp)
> >
> > save eax on the stack
> >
> > > movl -4(%ebp), %eax
> >
> > restore it
> >
> > > movl (%eax), %eax
> >
> > load eax from arg0
> >
> > > cmpl 8(%ebp), %eax
> >
> > compare eax with the memory at ebp+8
> >
> > > jne .L33
> >
> > So, the memory word at ebp+8 is compared with the memory at ebp+8.
> >
> > Do you have a debuuger that can single-step through this code, one
> > insn at a time?
>
> Sorry no debugger... this is a part of the 1st program running (well
> ... trying to run)
Well, we've established that whetever is wrong, it's not the code gcc
generates for this routine. It's correct, as you can see.
> The only debug ways usable in the code right now are some things like :
> i = (long)(fmt);
> __asm__ volatile ("mov %0, %%eax\n":: "m"(i));
> __asm__ volatile ("l1: jmp l1");
>
> which are really dirty i agree...
Thay're also wrong, becasue they don't clobber eax.
Andrew.
