GDB debugging multi-process and multithreading

Break line number: Set breakpoint

Clean line number: Clear Breakpoint

Info break: Show breakpoints

Finish: Exit function

BT: Viewing the function stack

Break function name, setting a breakpoint at the position of the function

Delete breakpoint Remove all breakpoints

Disable/enable Breakpoint 1 Enable breakpoint

Debugging a multi-process first method:

The set Detach-on-fork off enables simultaneous debugging of two processes, one running a block at the fork

Set Follow-fork-mode Parent/child by setting whether to debug a parent or child process

After Setup, query the process that is being debugged info inferior

Switch to the process you are debugging inferior number (the preceding number is not a process)

When you switch past processes to set breakpoints, C executes

The second method: You can easily debug any kind of process

By attach process number

Through this debugging, it is generally necessary to set the start position of the process to sleep for a period of time convenient attach, this operation requires root authority. The process number can be obtained by Pstree-ap | Prep Pthread

Also set the breakpoint at the location of the process to toggle past C execution

Multithreaded debugging:

Setting set scheduler-locking on first

A breakpoint is set inside the entry function or the entry function of the thread.

The program executes downward until the thread is generated (the breakpoint cannot be set directly C).

Info thread

Jump to the specified thread via thread 2

C execution

Internal commissioning

Return to main thread after commissioning

#include <stdio.h> #include <pthread.h>void processa (); void Processb (); void * Processaworker (void *arg);  int main (int argc, const char *argv[]) {int PID;  PID = fork ();  if (pid! = 0) Processa ();  else{Sleep (20);  PROCESSB ();  }//PROCESSB (); void Processa () {pid_t pid = Getpid ();  Char prefix[] = "Processa:";  Char tprefix[] = "thread";  int tstatus;  pthread_t pt;  printf ("%s%lu%s\n", prefix, PID, "Step1");  Tstatus = pthread_create (&pt, NULL, processaworker, NULL);    if (tstatus! = 0) {printf ("Processa:can not create new thread.");  }//Processaworker (NULL);  Sleep (1);  }void * Processaworker (void *arg) {pid_t pid = Getpid ();  pthread_t tid = pthread_self ();  Char prefix[] = "Processa:";  Char tprefix[] = "thread";  printf ("%s%lu%s%lu%s\n", prefix, PID, Tprefix, Tid, "Step2");  printf ("%s%lu%s%lu%s\n", prefix, PID, Tprefix, Tid, "step3");  return NULL;  }void Processb () {pid_t pid = Getpid ();  Char prefix[] = "PROCESSB:"; Printf("%s%lu%s\n", prefix, PID, "Step1");  printf ("%s%lu%s\n", prefix, PID, "Step2");  printf ("%s%lu%s\n", prefix, PID, "Step3"); }

Thread Debugging steps:

1.start

2.set scheduler-locking on

3.B 50 (internal to thread)

4.N until a new thread is generated

5.info thread

6.thread 2

7.c

8.n

9thread 1

There is one more command:

Thread apply ID1 ID 2 command

Debugging of the process:

1.start

2.set detach-on-fork off

3.b PROCESSB (This function can be set)

4.n

5.info inferior

6.inferior 2

7 C

If you want to change a process

Inferior other process numbers

Second: First set the wait time in front of the process you want to debug

1.sudo gdb Pthread

2.b 60 (to be set to internal)

3.fork after pstree-ap| grep pthread

Process number for 4.attach debugging

5. C

6. Internal commissioning

GDB debugging multi-process and multithreading