Tracing dynamic library functions with ltrace

Knowing the user-space library functions being called is as useful as knowing the system functions being invoked. The ltrace command provides a similar function to strace; however, it tracks user-space library calls instead of system calls.

Getting ready

Have the ltrace command installed using the Developer tools.

How to do it...

To trace user-space dynamic library calls, invoke the strace command, followed by the command you want to trace:

$ ltrace myApplication

The next example is a program with a subroutine:

$ cat test.c 
#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 

int print (char *str) { 
  printf("%s\n", str); 
} 
main () { 
  char *tmp; 
  tmp=malloc(100); 
  strcat(tmp, "testing"); 
  print(tmp); 
  free(tmp); 
  exit(0); 
} 
$ gcc test.c 
$ ltrace ./a.out 
(0, 0, 603904, -1, 0x1f25bc2)                            = 0x3b0de21160 
__libc_start_main(0x4005fe, 1, 0x7ffd334a95f8, 0x400660, 0x400650 <unfinished...