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，我认为这将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。你能用它们做的最好的事情就是知道它是哪个函数，但仅此而已。

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理解这种函数？

Answer 1

我会说您寻找的功能不太可能存在。要了解原因，请将代码更改为：

#define DEFINE_FUNCTION(type, struct_name, field_name)                \
void my_ ## type ## _function(struct struct_name *object, type value) \
{                                                                     \
    printf( "%s %d\n", # type, __LINE__ ); \
    printf( "%s %d\n", # type, __LINE__ ); \
}

DEFINE_FUNCTION(int, first, i_value);
DEFINE_FUNCTION(float, second, f_value);

void my_test_function(struct first *object, int value)
{
    printf( "test %d\n", __LINE__ );
    printf( "test %d\n", __LINE__ );
}

输出将是

test 24
test 25
int 19
int 19
float 20
float 20

重点是编译器把my_int_function看成一行代码，就好像你是这样写的

void my_int_function(struct struct_name *object, type value) { printf( "%s %d\n", "int", __LINE__ ); printf( "%s %d\n", "int", __LINE__ ); }

从多行宏到单行代码的转换是由预处理器执行的，因此当编译器开始分配行号时，您的函数已经是单行代码了。

事实上你可以用-E编译，看看预处理器做了什么。

有关参考，请参阅 C11 规范草案中的 5.1.1.2 翻译阶段 部分。

The precedence among the syntax rules of translation is specified by the following phases.⁶⁾

Physical source file multibyte characters are mapped, in an implementation- defined manner, to the source character set (introducing new-line characters for end-of-line indicators) if necessary. Trigraph sequences are replaced by corresponding single-character internal representations.

Each instance of a backslash character () immediately followed by a new-line character is deleted, splicing physical source lines to form logical source lines. [...]

6) Implementations shall behave as if these separate phases occur, even though many are typically folded together in practice. [...]

Answer 2

我通过以下方式解决了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/ 把#includes 放回去

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。

以上听起来很麻烦，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 ide 中的错误跳转到生成的代码，这通常很烦人。

如何将 valgrind 与实际上是宏扩展的函数一起使用

How to use valgrind with a function that is actually the expansion of a macro

c

macros

gcc

valgrind