Compiled mytest with FreeBSD clang version 3.3 that uses a shared library (based on mylib.c). The assembly and the lldb symbol lookup don't seem to match, i.e. the instruction at address 0x400878 uses "a" in 0x600c08, which is in the range of mytest (rather than the shared library where "a" is held at 0x0000000800a1b820). Note: using gdb shows t…

lldb

(lldb) bt
* thread #1: tid = 12678, 0x0000000000400878 mytest`main + 40 at mytest.c:10, stop reason = breakpoint 1.1
    frame #0: 0x0000000000400878 mytest`main + 40 at mytest.c:10
    frame #1: 0x000000000040076f mytest`_start + 335
(lldb) di -l
mytest`main + 40 at mytest.c:10
   9        j=get_a();
-> 10       if (a==i) {
   11       // nop
-> 0x400878:  movl   0x600c08, %eax
   0x40087f:  cmpl   -0x8(%rbp), %eax
   0x400882:  jne    0x40088d                  ; main + 61 at mytest.c:12
(lldb) im loo -a 0x600c080
(lldb) p/x &a
(int *) $1 = 0x0000000800a1b820
(lldb) im loo -a 0x800a1b820
      Address: libbss.so.1[0x0000000000200820] (libbss.so.1..bss + 0)
      Summary: libbss.so.1`a
(lldb) p/x a
(int) $2 = 0x00000000
(lldb) p/x i
(int) $3 = 0x00000001
(lldb) expr -- a == i
(bool) $4 = false
(lldb) expr -- i == j
(bool) $5 = true
(lldb) c
(lldb) a: 1, i: 1, j:1

mylib.c

#include "mylib.h"

int a;

void set_a(int i){
    a=i;
}

int get_a(){
    return a;
}

mylib.h

extern int a;

void set_a(int i);
int get_a();

mytest.c

#include <stdio.h>
#include "../lib/mylib.h"

int main () {
    int i,j;

    i=1;
    set_a(i);
    j=get_a();
    if (a==i) {
    // nop
    }
    printf("a: %d, i: %d, j:%d\n",a, i, j);
    return 0;
}