gdb除錯多程序和多執行緒命令
阿新 • • 發佈:2019-01-08
原文地址:http://blog.csdn.net/pbymw8iwm/article/details/7876797
1. 預設設定下,在除錯多程序程式時GDB只會除錯主程序。但是GDB(>V7.0)支援多程序的分別以及同時除錯,換句話說,GDB可以同時除錯多個程式。只需要設定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 只調試主程序(GDB預設)
child on 只調試子程序
parent off 同時除錯兩個程序,gdb跟主程序,子程序block在fork位置
child off 同時除錯兩個程序,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]
查詢正在除錯的程序:info inferiors
切換除錯的程序: inferior <infer number>
新增新的除錯程序: add-inferior [-copies n] [-exec executable] ,可以用file executable來分配給inferior可執行檔案。
其他:remove-inferiors infno, detach inferior
2. GDB預設支援除錯多執行緒,跟主執行緒,子執行緒block在create thread。
查詢執行緒:info threads
切換除錯執行緒:thread <thread number>
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);
}
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");
}
輸出:
[[email protected] c-lab]$ ./test
ProcessA: 802 step1
ProcessB: 803 step1
ProcessB: 803 step2
ProcessB: 803 step3
ProcessA: 802 thread 3077555904 step2
ProcessA: 802 thread 3077555904 step3
ProcessA: 802 thread 3077553008 step2
ProcessA: 802 thread 3077553008 step3
除錯:
1. 除錯主程序,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
Missing separate debuginfos, use: debuginfo-install glibc-2.12-1.47.el6.i686
(gdb) info inferiors
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 ?? ()
(gdb) info inferiors
Num Description Executable
* 2 process 3475 /home/cnwuwil/labs/c-lab/test
1 process 3472 /home/cnwuwil/labs/c-lab/test
(gdb) inferior 1
[Switching to inferior 1 [process 3472] (/home/cnwuwil/labs/c-lab/test)]
[Switching to thread 1 (Thread 0xb7fe86c0 (LWP 3472))]
#0 main (argc=1, argv=0xbffff364) at test.c:14
(gdb) info inferiors
Num Description Executable
2 process 3475 /home/cnwuwil/labs/c-lab/test
* 1 process 3472 /home/cnwuwil/labs/c-lab/test
3. 設斷點繼續除錯主程序,主程序產生兩個子執行緒:
(gdb) break test.c:50
Breakpoint 3 at 0x804867d: file test.c, line 50. (2 locations)
(gdb) cont
ProcessA: 3472 step1
[New Thread 0xb7fe7b70 (LWP 3562)]
ProcessA: 3472 thread 3086911168 step2
Breakpoint 3, processAworker (arg=0x0) at test.c:50
(gdb) info inferiors
Num Description Executable
2 process 3475 /home/cnwuwil/labs/c-lab/test
* 1 process 3472 /home/cnwuwil/labs/c-lab/test
(gdb) 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執行緒,注意:執行緒2為前面產生的子程序
(gdb) thread 3
[Switching to thread 3 (Thread 0xb7fe7b70 (LWP 3562))]#0 0x00110424 in __kernel_vsyscall ()
(gdb) 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
(gdb) info threads
* 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 __kernel_vsyscall ()
(gdb) thread 1