Linux下用内存管理器的钩子函数跟踪内存泄漏

Linux下用内存管理器的钩子函数跟踪内存泄漏
[日期：2009-12-20] 来源：CSDN  作者：李先静

作者联系方式：李先静 <xianjimli at hotmail dot com>

作为Linux下的C程序员，我总是习惯在单元测试通过之后，再用valgrind把程序跑一下，看看有没有内存泄漏和内存越界等问题。可惜的是，有时valgrind并不能很好的工作，像基于DirectFB的多进程程序在valgrind下是跑不起的, 这时我们可以通过内存管理器的钩子函数来跟踪内存泄漏。

glibc提供的内存管理器的钩子函数让你可以监控/改变内存管理函数的行为。其实glibc已经利用这个机制实现了内存泄漏检测的功能，提供了mtrace/muntrace两个函数和mtrace工具，只是不太好用，一是速度慢，二是没有backtrace。更惨的是在Fedora 7上再也找不到它了，只好自己写一个：

先记录分配/释放操作：

/**//*memory_trace.c*/

#include <execinfo.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <malloc.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>

static void  memory_trace_init(void);
static void  memory_trace_deinit(void);
static void *my_malloc_hook (size_t size, const void* ptr);
static void  my_free_hook (void* ptr, const void* caller);
static void *my_realloc_hook (void *ptr, size_t size, const void *caller);

static void *my_malloc_hook (size_t size, const void* ptr);
static void  my_free_hook (void* ptr, const void* caller);
static void *my_realloc_hook (void *ptr, size_t size, const void *caller);

static void *(*old_malloc_hook)(size_t size, const void* ptr);
static void  (*old_free_hook)(void* ptr, const void* caller);
static void *(*old_realloc_hook)(void *ptr, size_t size, const void *caller);

#define BACK_TRACE_DEPTH 8
#define CACHE_SIZE       512

static FILE* g_memory_trace_fp = NULL;
static int   g_memory_trace_cache_used = 0;
/**//*additional 3 items: alloc/free addr size*/
static void* g_memory_trace_cache[CACHE_SIZE][BACK_TRACE_DEPTH + 3];
static void  memory_trace_flush(void);
static void  memory_trace_write(int alloc, void* addr, int size);

static void memory_trace_backup(void)
...{
    old_malloc_hook  = __malloc_hook;
    old_free_hook    = __free_hook;
    old_realloc_hook = __realloc_hook;

    return;
}

static void memory_trace_hook(void)
...{
    __malloc_hook  = my_malloc_hook;
    __free_hook    = my_free_hook;
    __realloc_hook = my_realloc_hook;

    return;
}

static void memory_trace_restore(void)
...{
    __malloc_hook  = old_malloc_hook;
    __free_hook    = old_free_hook;
    __realloc_hook = old_realloc_hook;

    return;
}

static void memory_trace_init(void)
...{
    if(g_memory_trace_fp == NULL && getenv("MALLOC_TRACE") != NULL)
    ...{
        char file_name[260] = ...{0};
        snprintf(file_name, sizeof(file_name), "/tmp/%d_memory.log", getpid());
        if((g_memory_trace_fp = fopen(file_name, "wb+")) != NULL)
        ...{
            memory_trace_backup();
            memory_trace_hook();
        }

        atexit(memory_trace_deinit);
    }

    return;
}

static void memory_trace_deinit(void)
...{
    if(g_memory_trace_fp != NULL)
    ...{
        memory_trace_restore();
        memory_trace_flush();
        fclose(g_memory_trace_fp);
        g_memory_trace_fp = NULL;
    }

    return;
}

void (*__malloc_initialize_hook) (void) = memory_trace_init;

static void * my_malloc_hook (size_t size, const void *caller)
...{
    void *result = NULL;
    memory_trace_restore();
    result = malloc (size);
    memory_trace_write(1, result, size);
    memory_trace_hook();
   
    return result;
}

static void my_free_hook (void *ptr, const void *caller)
...{
    memory_trace_restore();
    free (ptr);
    memory_trace_write(0, ptr, 0);
    memory_trace_hook();

    return;
}

static void *my_realloc_hook (void *ptr, size_t size, const void *caller)
...{
    void* result = NULL;

    memory_trace_restore();
    memory_trace_write(0, ptr, 0);
    result = realloc(ptr, size);
    memory_trace_write(1, result, size);
    memory_trace_hook();

    return result;
}

static void memory_trace_flush_one_entry(int index)
...{
    int offset = 0;
    char buffer[512] = ...{0};
    int fd = fileno(g_memory_trace_fp);
    int alloc  = (int)g_memory_trace_cache[index][BACK_TRACE_DEPTH];
    void* addr = g_memory_trace_cache[index][BACK_TRACE_DEPTH+1];
    int size   = (int)g_memory_trace_cache[index][BACK_TRACE_DEPTH+2];
    void** backtrace_buffer = g_memory_trace_cache[index];

    snprintf(buffer, sizeof(buffer), "%s %p %d ", alloc ? "alloc":"free", addr, size);
    if(!alloc)
    ...{
        write(fd, buffer, strlen(buffer));
        return;
    }
   
    char** symbols = backtrace_symbols(backtrace_buffer, BACK_TRACE_DEPTH);
    if(symbols != NULL)
    ...{
        int i = 0;
        offset = strlen(buffer);
        for(i = 0; i < BACK_TRACE_DEPTH; i++)
        ...{
            if(symbols[i] == NULL)
            ...{
                break;
            }
            char* begin = strchr(symbols[i], '(');
            if(begin != NULL)
            ...{
                *begin = ' ';
                char* end = strchr(begin, ')');
                if(end != NULL)
                ...{
                    strcpy(end, " ");
                }
                strncpy(buffer+offset, begin, sizeof(buffer)-offset);
                offset += strlen(begin);
            }
        }
        write(fd, buffer, offset);
        free(symbols);
    }

    return;
}

static void memory_trace_flush(void)
...{
    int i = 0;
    for(i = 0; i < g_memory_trace_cache_used; i++)
    ...{
        memory_trace_flush_one_entry(i);
    }
    g_memory_trace_cache_used = 0;

    return;
}

static void memory_trace_write(int alloc, void* addr, int size)
...{
    if(g_memory_trace_cache_used >= CACHE_SIZE)
    ...{
        memory_trace_flush();
    }

    int i = 0;
    void* backtrace_buffer[BACK_TRACE_DEPTH] = ...{0};
    backtrace(backtrace_buffer, BACK_TRACE_DEPTH);

    for(i = 0; i < BACK_TRACE_DEPTH; i++)
    ...{
        g_memory_trace_cache[g_memory_trace_cache_used][i] = backtrace_buffer[i];
    }
    g_memory_trace_cache[g_memory_trace_cache_used][BACK_TRACE_DEPTH] = (void*)alloc;
    g_memory_trace_cache[g_memory_trace_cache_used][BACK_TRACE_DEPTH+1] = addr;
    g_memory_trace_cache[g_memory_trace_cache_used][BACK_TRACE_DEPTH+2] = (void*)size;

    g_memory_trace_cache_used++;

    return;
}

#ifdef MEMORY_TRACE_TEST
void test(void)
...{
    char* p = malloc(100);
    p = malloc(123);

    free(p);

    return;
}
int main(int argc, char* argv[])
...{
    malloc(100);
    test();
    malloc(100);
    test();
    char* p = malloc(100);
    free(p);
   
    return 0;
}
#endif/*MEMORY_TRACE_TEST*/

把以上代码编译成动态库，或者直接编译到功能代码一起。如果设置了MALLOC＿TRACE环境变量，分配/释放会被记录到/tmp/$PID_memory.log下。

再写个程序来分析log文件：
/**//*mtrace.c*/
#include <stdio.h>

#define MAX_ENTRY 1024*1024

int main(int argc, char* argv[])
...{
    if(argc != 3)
    ...{
        printf("usage: %s [log file] [out file] ", argv[0]);
        return 0;
    }

    FILE* fp     = fopen(argv[1], "r");
    FILE* fp_out = fopen(argv[2], "wb+");

    if(fp == NULL || fp_out == NULL)
    ...{
        printf("open file failed ");
        if(fp != NULL)
        ...{
            fclose(fp);
        }
        if(fp_out != NULL)
        ...{
            fclose(fp_out);
        }
        return;
    }

    int   i = 0;
    int   n = 0;
    int   skip = 0;
    int   line_index = 0;
    void* addr = 0;
    char  line[260] = ...{0};
    void* addrs_array[MAX_ENTRY] = ...{0};
    int   lines_array[MAX_ENTRY] = ...{0};

    while(fgets(line, sizeof(line), fp) != NULL)
    ...{
        if(line[0] != 'a' && line[0] != 'f')
        ...{
            line_index++;
            continue;
        }

        addr = NULL;
        if(strncmp(line, "alloc", 5) == 0 && n < MAX_ENTRY)
        ...{
            sscanf(line, "alloc %p", &addr);
            addrs_array[n] = addr;
            lines_array[n] = line_index;
            n++;
           
            printf("a");
        }
        else if(strncmp(line, "free", 4) == 0)
        ...{
            sscanf(line, "free %p", &addr);
            for(i = 0; i < n; i++)
            ...{
                if(addrs_array[i] == addr)
                ...{
                    lines_array[i] = -1;
                    break;
                }
            }

            printf("f");
        }
        line_index++;
    }

    printf(" ");
    fseek(fp, 0, 0);

    i = 0;
    line_index = 0;
    while(fgets(line, sizeof(line), fp) != NULL)
    ...{
        if(strncmp(line, "alloc", 5) == 0)
        ...{
            if(lines_array[i] == line_index)
            ...{
                printf("leak %s", line);
                fprintf(fp_out, "*");
                skip = 0;
                i++;
            }
            else
            ...{
                skip = 1;
            }
        }
        else if(strncmp(line, "free", 4) == 0)
        ...{
            skip = 1;
        }

        if(!skip)
        ...{
            fputs(line, fp_out);
        }

        line_index++;
    }

    fclose(fp);
    fclose(fp_out);

    return 0;
}
把这个段代码编译成一个可执行文件mtrace，以前面记录的LOG为输入，再指定个输出文件，内存泄漏会被写到输出文件中，可以看到内存泄漏的地地址，大小和调用关系。

本篇文章来源于 Linux公社网站(www.linuxidc.com)  原文链接：http://www.linuxidc.com/Linux/2009-12/23575.htm