将 GDB 与 OpenMP 一起使用 [英] Using GDB with OpenMP

问题描述

使用 GDB，我似乎无法在 OpenMP 线程中打印共享变量的值.例如，使用以下程序:

Using GDB I can't seem to print the value of shared variables within OpenMP threads. For example, using the following program:

#include <omp.h>
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[]) {
  int priv, tid, pub = 100;
  #pragma omp parallel private(priv, tid) num_threads(2)
  {
    tid = omp_get_thread_num();
    priv = tid * 10; 
    #pragma omp sections
    {
      #pragma omp section
      {
        printf("SECTION 0: tid=%d, priv=%d, pub=%d
", tid, priv, pub);
      }
      #pragma omp section
      {
        printf("SECTION 1: tid=%d, priv=%d, pub=%d
", tid, priv, pub);
      }

    }
  }
  return EXIT_SUCCESS;
}

在 GDB 中，如果我在第 15 行中断(第 0 节的 printf)，并尝试打印 "pub" 的值，我会得到 «No symbol "pub" in current context.»留言:

In GDB, if I break at line 15 (the printf of section 0), and I try to print the value of "pub", I get the «No symbol "pub" in current context.» message:

Breakpoint 1, main._omp_fn.0 () at omp_simplesec.c:15
15          printf("SECTION 0: tid=%d, priv=%d, pub=%d
", tid, priv, pub);
(gdb) print pub
No symbol "pub" in current context.

我正在使用 GCC 编译，并尝试了不同的调试标志 (-g3 -ggdb3 -gstabs3 -gstabs+3)，但没有成功.我还尝试使用 -O0 禁用所有优化，但同样没有成功.但是，我可以使用 -gstabs+ 标志查看私有变量的值.

I am compiling with GCC, and tried different debugging flags (-g3 -ggdb3 -gstabs3 -gstabs+3), without success. I also tried disabling all optimizations with -O0, again with no success. However, I can see the value of private variables by using the -gstabs+ flag.

提前致谢.

推荐答案

当我运行你的代码时，我得到了类似的结果.如果您查看回溯，它会告诉您您处于与 GCC 如何实现 OpenMP 相关的 OpenMP 环境中.

When I run your code I get similar results. If you look at the backtrace, it tells you that you are inside an OpenMP environment that is related to how GCC implements OpenMP.

(gdb) backtrace 
#0  main._omp_fn.0 () at tmp.c:15
#1  0x000000000040082e in main (argc=1, argv=0x7fffffffe6c8) at tmp.c:7

您可以通过以下方式获取 pub 的值:

You can get a value of pub by:

(gdb) up
(gdb) print pub
$1 = 100

但这只会让您在并行区域之前获得 pub 的值.您应该查看 Hristo Iliev 的答案，以获得更详细和更好的情况描述.

but this only gets you the value of pub before the parallel region. You should check the answer by Hristo Iliev for a much more detailed and better description of the situation.

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