gdb調試多程序和多線程指令

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1.

預設設定下，在調試多程序程式時GDB隻會調試主程序。但是GDB（>V7.0）支援多程序的分别以及同時調試，換句話說，GDB可以同時調試多個程式。隻需要設定follow-fork-mode(預設值：parent)和detach-on-fork（預設值：on）即可。

      follow-fork-mode  detach-on-fork   說明

parent                   on               隻調試主程序（GDB預設）

child                     on               隻調試子程序

parent                   off              同時調試兩個程序，gdb跟主程序，子程序block在fork位置

child                     off

             同時調試兩個程序，gdb跟子程序，主程序block在fork位置

   設定方法：set follow-fork-mode [parent|child]

  set detach-on-fork

[on|off]

   查詢正在調試的程序：info

inferiors

   切換調試的程序： inferior <infer

number>

   添加新的調試程序： add-inferior [-copies n]

[-exec executable] ,可以用file

executable來配置設定給inferior可執行檔案。

   其他：remove-inferiors

infno， detach inferior

2. GDB預設支援調試多線程，跟主線程，子線程block在create

thread。

   查詢線程：info

threads

   切換調試線程：thread <thread

例程：

#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

    processB();

  return

0;

  }

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);

* processAworker(void *arg)

  pid_t pid =

getpid();

  pthread_t tid = pthread_self();

prefix[] = "ProcessA: ";

  char tprefix[] = "thread

";

  printf("%s%lu %s%lu %s\n", prefix, pid, tprefix, tid,

"step2");

"step3");

  return NULL;

processB()

  char prefix[] = "ProcessB:

輸出：

[cnwuwil@centos c-lab]$ ./test

ProcessA: 802 step1

ProcessB: 803 step1

ProcessB: 803

step2

ProcessB: 803 step3

ProcessA: 802 thread 3077555904

ProcessA: 802 thread 3077555904 step3

ProcessA: 802 thread

3077553008 step2

ProcessA: 802 thread 3077553008 step3

調試：

1. 調試主程序，block子程序。

(gdb) set detach-on-fork off

(gdb) show detach-on-fork

Whether gdb

will detach the child of a fork is off.

(gdb) catch fork

Catchpoint 1

(fork)

(gdb) r

[Thread debugging using libthread_db

enabled]

Catchpoint 1 (forked process 3475), 0x00110424 in

__kernel_vsyscall ()

Missing separate debuginfos, use: debuginfo-install

glibc-2.12-1.47.el6.i686

(gdb) break test.c:14

Breakpoint 2 at 0x8048546:

file test.c, line 14.

(gdb) cont

[New process 3475]

[Thread debugging

using libthread_db enabled]

Breakpoint 2, main (argc=1, argv=0xbffff364)

at test.c:14

(gdb) info

  Num  Description       Executable       

  2    process

3475      /home/cnwuwil/labs/c-lab/test

*

1    process

3472      /home/cnwuwil/labs/c-lab/test

2. 切換到子程序：

(gdb) inferior 2

[Switching to inferior 2 [process 3475]

(/home/cnwuwil/labs/c-lab/test)]

[Switching to thread 2 (Thread 0xb7fe86c0

(LWP 3475))]

#0  0x00110424 in ?? ()

2    process

  1    process

(gdb)

inferior 1

[Switching to inferior 1 [process 3472]

[Switching to thread 1 (Thread 0xb7fe86c0

(LWP 3472))]

#0  main (argc=1, argv=0xbffff364) at

test.c:14

3. 設斷點繼續調試主程序，主程序産生兩個子線程：

(gdb) break test.c:50

Breakpoint 3 at 0x804867d: file test.c, line 50.

(2 locations)

ProcessA: 3472 step1

[New Thread 0xb7fe7b70

(LWP 3562)]

ProcessA: 3472 thread 3086911168 step2

Breakpoint 3,

processAworker (arg=0x0) at test.c:50

info threads

  3 Thread 0xb7fe7b70 (LWP 3562)  0x00110424

in __kernel_vsyscall ()

  2 Thread 0xb7fe86c0 (LWP

3475)  0x00110424 in ?? ()

* 1 Thread 0xb7fe86c0 (LWP

3472)  processAworker (arg=0x0) at test.c:50

4. 切換到主程序中的子線程，注意：線程2為前面産生的子程序

(gdb) thread 3

[Switching to thread 3 (Thread 0xb7fe7b70 (LWP

3562))]#0  0x00110424 in __kernel_vsyscall ()

cont

ProcessA: 3472 thread 3086911168 step3

ProcessA: 3472 thread

3086908272 step2

[Switching to Thread 0xb7fe7b70 (LWP

3562)]

Breakpoint 3, processAworker (arg=0x0) at test.c:50

* 3 Thread 0xb7fe7b70 (LWP 3562)  processAworker (arg=0x0)

at test.c:50

  2 Thread 0xb7fe86c0 (LWP 3475)  0x00110424

in ?? ()

  1 Thread 0xb7fe86c0 (LWP 3472)  0x00110424 in

(gdb) thread 1