m2 macos 13.4.1 use lldb debug c program terminated by signal 5

Question

My problem

• when i use lldb to debug a c program, i use function fork() execl() in a main function in macos m2, lldb terminated by signal 5
• but when i use x86 ubuntu system, the same code, Both gdb and lldb work properly

My code

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int main() {
  pid_t childpid;
  int fd[2];
  if ((pipe(fd) == -1) || ((childpid = fork()) == -1)) {
    perror("Failed to setup pipeline");
    return 1;
  }
  if (childpid == 0) {
    if (dup2(fd[1], STDOUT_FILENO) == -1)
      perror("Failed to redirect stdout of ls");
    if ((close(fd[0]) == -1) || (close(fd[1])) == -1)
      perror("Failed to close extra pipe descriptors on ls");
    else {
      execl("/bin/ls", "ls", "-l", NULL);
      perror("Failed to exec ls");
    }
    return 1;
  }
  if (dup2(fd[0], STDIN_FILENO) == -1)
    perror("Failed to redirect stdin of sort");
  if ((close(fd[0]) == -1) || (close(fd[1]) == -1))
    perror("Failed to close extra pipe descriptors on sort");
  else {
    execl("/usr/bin/sort", "sort", "-n", "+4", NULL);
    perror("Failed to exec sort");
  }
  return 1;
}

Run detail info

• run program directly shows:

➜   ./simpleredirect
total 104
drwxr-xr-x  3 tonghui  staff     96  7 23 15:24 simpleredirect.dSYM
-rw-r--r--@ 1 tonghui  staff    747  7 22 11:32 parentwritepipe.c
-rw-r--r--@ 1 tonghui  staff    989  7 23 16:28 simpleredirect.c
-rw-r--r--@ 1 tonghui  staff    999  7 22 13:17 synchronizefan_pipe.c
-rw-r--r--@ 1 tonghui  staff   1033  7 23 13:14 simpleredirect_1.c
-rwxr-xr-x  1 tonghui  staff  34059  7 23 16:28 simpleredirect

• use lldb to debug

➜   lldb simpleredirect
(lldb) target create "simpleredirect"
Current executable set to '/Users/specialfile/simpleredirect' (arm64).
(lldb) r
Process 49076 launched: '/Users/workspace/code-container/c/unix/specialfile/simpleredirect' (arm64)
Process 49076 exited with status = 5 (0x00000005) Terminated due to signal 5
(lldb) n
error: Command requires a process which is currently stopped.

• please help me，thanks！

lldb terminated Process 49190 exited with status = 5 (0x00000005) Terminated due to signal 5

Answer 1

darwin systems don't allow binaries to be debugged by default. They either have to be ad hoc codesigned, or signed with the get-task-allow entitlement set to "true". System binaries are always codesigned by Apple and generally don't have that entitlement, and so can't be debugged. If you really need to debug a system binary you have to turn off SIP.

The way you've written your code, you execl /usr/bin/ls in the forked child (which would be fine) AND /usr/bin/sort on the parent side of the fork at line 27.

When you are running under the debugger and try to exec as opposed to fork/exec a system binary, your program will get killed in exec, otherwise that would provide a backhand way to debug a system binary that didn't opt into being debugged. Your program gets killed in a not very helpful way, because the system doesn't want the give the debugger any leeway to try to make the debug session work somehow, so it terminates it with "extreme prejudice".