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Date: Fri, 16 May 2008 15:32:00 -0000
From: Aleksandar Ristovski <aristovski@qnx.com>
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Subject: Frame lost after 'leave' and before 'ret' instruction on i386?
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Hello,

I noticed that after 'leave' asm instruction (and before 'ret') one frame will be lost (skipped).

For example:

(gdb) disassemble doSth
Dump of assembler code for function doSth:
0x080484f4 <doSth+0>:   push   %ebp
0x080484f5 <doSth+1>:   mov    %esp,%ebp
0x080484f7 <doSth+3>:   sub    $0x8,%esp
0x080484fa <doSth+6>:   sub    $0xc,%esp
0x080484fd <doSth+9>:   push   $0x8048570
0x08048502 <doSth+14>:  call   0x8048348 <printf@plt>
0x08048507 <doSth+19>:  add    $0x10,%esp
0x0804850a <doSth+22>:  leave
0x0804850b <doSth+23>:  ret
End of assembler dump.
(gdb) info registers
...
eip            0x804850b        0x804850b <doSth+23>
...
(gdb) bt
#0  0x080483c3 in doSth () at main.c:6
#1  0xb7ebffdc in __libc_start_main () from /lib/libc.so.6
#2  0x08048331 in _start ()

(note 'main' that really made the call is missing... e.g., just before "leave" was executed:
(gdb) bt
#0  doSth () at main.c:6
#1  0x080483da in main () at main.c:10
)

What happens is, we have restored the stack pointer but gdb is unaware of that fact and tries to unwind using already unwound value...

how is this supposed to work?