ISAAC GELADO FERNANDEZ wrote:
De: Chungwei Hsiung <[EMAIL PROTECTED]>
Fecha: Viernes, Marzo 5, 2004 7:43 pm
I have a simple test program. I compile it,
and
gdb to disassemble main. I got the following..
0x80481f8 <main>: push %ebp
0x80481f9 <main+1>: mov %esp,%ebp
0x80481fb <main+3>: sub $0x8,%esp
0x80481fe <main+6>: and $0xfffffff0,%esp
0x8048201 <main+9>: mov $0x0,%eax
0x8048206 <main+14>: sub %eax,%esp
I don't know if at line 5, we move zero to %eax. why do we need to sub %eax, %esp? why do we need to subtract 0 from the stack pointer??
I am no really sure, but it maybe be because you don't have any local variable, so it is no necessary to allocate memory in the stack for them. This seems a pattern from the compiler, it subtract the size of local variables from the stack pointer, so when there is none it subtracts zero. But this is just a supposition
Regards,
Isaac
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