In the disassembly there's such code:
movl $0x6,-0x4(%rbp)
I try to print the value this way but fails:
(gdb) p 0x4(%esp)
A syntax error in expression, near `%开发者_如何学JAVAesp)'.
(gdb) p 0x4+$esp
Argument to arithmetic operation not a number or boolean.
How to print it correctly?
It looks like you're working with 64 bit code, in which case you just need, e.g.:
(gdb) p $rbp-0x4
$1 = (void *) 0x7fff5fbff71c
If you want to see what's actually at this address, then you need to cast the void *
address, e.g.
(gdb) p /x *(int *)($rbp-0x4)
$2 = 0x7fff
or, more succinctly, use x
instead of p
, e.g.
(gdb) x /w $rbp-0x4
0x7fff5fbff71c: 0x00007fff
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