c - 如何将 valgrind 与实际上是宏扩展的函数一起使用

Question

让我们从一个例子开始，我认为这会立即说明我正在处理的问题。这是一个简单的测试程序，与现实相差甚远，但确实很好地说明了问题

 1    #include <stdio.h>
 2    #include <stdlib.h>
 3    
 4    struct first {
 5        int i_value;
 6    };
 7    
 8    struct second {
 9        float f_value;
10    };
11    
12    #define DEFINE_FUNCTION(type, struct_name, field_name)                \
13    void my_ ## type ## _function(struct struct_name *object, type value) \
14    {                                                                     \
15        /* Deliberately read an uninitialized value to make valgrind  */  \
16        /* report the issue                                           */  \
17        if (object->field_name == -1)                                     \
18            return;                                                       \
19        object->field_name = value;                                       \
20    }
21    
22    DEFINE_FUNCTION(int, first, i_value);
23    DEFINE_FUNCTION(float, second, f_value);
24    
25    void
26    my_test_function(struct first *object, int value)
27    {
28        /* Deliberately read an uninitialized value to make valgrind  */
29        /* report the issue                                           */
30        if (object->i_value == -1)
31            return;
32        object->i_value = value;
33    }
34    
35    int
36    main(void)
37    {
38        struct first frst;
39        struct second scnd;
40    
41        my_test_function(&frst, -5);
42        my_int_function(&frst, -2);
43        my_float_function(&scnd, 3.0);
44    
45        return 0;
46    }

如果你编译这段代码并使用

valgrind --show-origins=yes ./compiled-program

你会看到这样的输出

==25304== Memcheck, a memory error detector
==25304== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==25304== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==25304== Command: ./macro-valgrind
==25304== 
==25304== Conditional jump or move depends on uninitialised value(s)
==25304==    at 0x40056F: my_test_function (macro-valgrind.c:30)
==25304==    by 0x400597: main (macro-valgrind.c:41)
==25304==  Uninitialised value was created by a stack allocation
==25304==    at 0x40057F: main (macro-valgrind.c:37)
==25304== 
==25304== Conditional jump or move depends on uninitialised value(s)
==25304==    at 0x40053A: my_float_function (macro-valgrind.c:23)
==25304==    by 0x4005BC: main (macro-valgrind.c:43)
==25304==  Uninitialised value was created by a stack allocation
==25304==    at 0x40057F: main (macro-valgrind.c:37)
==25304== 
==25304== Conditional jump or move depends on uninitialised value(s)
==25304==    at 0x400547: my_float_function (macro-valgrind.c:23)
==25304==    by 0x4005BC: main (macro-valgrind.c:43)
==25304==  Uninitialised value was created by a stack allocation
==25304==    at 0x40057F: main (macro-valgrind.c:37)
==25304== 
==25304== 
==25304== HEAP SUMMARY:
==25304==     in use at exit: 0 bytes in 0 blocks
==25304==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==25304== 
==25304== All heap blocks were freed -- no leaks are possible
==25304== 
==25304== For counts of detected and suppressed errors, rerun with: -v
==25304== ERROR SUMMARY: 3 errors from 3 contexts (suppressed: 0 from 0)

正如您在上面的 valgrind 输出中看到的，报告的第一个未初始化读取来自 my_test_function() 函数，它显示了发生问题的确切行。这样修复代码就相当容易了。其他报道显然无法理解。您最多只能知道它是哪个函数，仅此而已。

我知道生成的代码令人困惑 valgrind这就是为什么我的实际问题是，

• 有没有办法用gcc编译代码？可以帮助 valgrind 理解这类函数吗？

Answer 1

我通过以下方式解决这种由宏引起的调试问题:

1/注释掉标准库/第三方#includes

2/通过 gcc -E -C -P，展开宏

3/放回#includes

4/通过 clang-format，打断很长的行

5/编译带调试信息

程序和以前一样，只是gdb和valgrind引用了扩展源。然后很容易找到错误，然后使用 diff 工具将其追溯到原始来源。

上面的内容听起来很麻烦，但步骤 1 到 4 与步骤 5 一样可编写脚本，因此开发期间的实际开销很小。这不是我的默认设置的原因是跳转到 ide 中的错误会将我带到生成的代码，这通常很烦人。