c - 程序通过 valgrind memcheck 提前终止

Question

我有一个 C 程序(很多数字，太长无法发布)，我用它编译

gcc -g -O0 program.c -o program

我正在尝试使用 gdb 和 valgrind memcheck 对其进行调试。在对代码进行一些更改后，我发现

valgrind --tool=memcheck --log-file=output.log ./program

给予

==15866== Memcheck, a memory error detector
==15866== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==15866== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==15866== Command: ./program
==15866== Parent PID: 3362
==15866== 
==15866== Warning: client switching stacks?  SP change: 0xbe88bcd8 --> 0xbe4e1f70
==15866==          to suppress, use: --max-stackframe=3841384 or greater
==15866== Invalid write of size 4
==15866==    at 0x804B7BE: main (program.c:1396)
==15866==  Address 0xbe4e1f74 is on thread 1's stack
==15866== 
==15866== Invalid write of size 4
==15866==    at 0x804B7C2: main (program.c:1396)
==15866==  Address 0xbe4e1f70 is on thread 1's stack
==15866== 
==15866== Invalid read of size 4
==15866==    at 0x4320011: on_exit (on_exit.c:34)
==15866==    by 0x43064D2: (below main) (libc-start.c:226)
==15866==  Address 0xbe4e1f70 is on thread 1's stack
==15866== 
==15866== Invalid read of size 4
==15866==    at 0x4320022: on_exit (on_exit.c:37)
==15866==    by 0x43064D2: (below main) (libc-start.c:226)
==15866==  Address 0xbe4e1f74 is on thread 1's stack

还有很多这样的。

valgrind --tool=memcheck --max-stackframe=3841384 --log-file=output.log ./program

不打印任何错误。但让我感到困惑的是，对于两个 valgrind 调用，程序提前退出(没有错误消息)并且不执行它应该执行的计算。具有相同编译器选项但在没有 valgrind 的情况下运行的行为是完全不同的，看起来很正常。但是我怀疑内存错误并想使用 valgrind 来找到它。因此，我的问题是:在使用 valgrind 执行时，什么样的错误会使程序表现如此不同？如果这些是与内存相关的错误，我该如何识别呢？请注意，我很清楚我可以“手动调试”来定位它。但是我是否可以使用 valgrind 运行 gdb 以查看它退出的位置。

Answer 1

我最初在评论中回答:

You're probably causing a stack overflow. Are you allocating "large" arrays on the stack? E.g. double myArray[10000000]; If so then you should replace such allocations with heap memory using malloc and free.

我写了一个简短的 c 程序来故意造成这样的堆栈溢出并检查 valgrind 报告的内容:

#include <stdio.h>

int main(){

  // imax*sizeof(double) is too big for the stack.
  int imax = 10000000;
  double test[imax];

  // I do a little math to prevent the stack overflow from being optimized away if -O3 is used.
  test[0]=0;
  test[1]=1;
  for(int i=2; i<imax; i++)
    test[i]=0.5*(test[i-1]+test[i-2]);
  printf("%e\n", test[imax-1]);

}

果然，valgrind 得出了:

==83869== Warning: client switching stacks?  SP change: 0x104802930 --> 0xffbb7520
==83869==          to suppress, use: --max-stackframe=80000016 or greater
==83869== Invalid write of size 8
==83869==    at 0x100000ED0: main (in ./a.out)
==83869==  Address 0xffbb7520 is on thread 1's stack

连同大量其他错误消息，并最终以 Segmentation fault: 11

退出