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在C语言中设计动态内存申请失败相关的单元测试

Charles Chan @ 2022-12-12 #C/C++ #malloc #UnitTest @Program

Contents:

需要注意的只有一点：

dlsym会使用calloc函数。因此，calloc的指针必须在第一次使用之前就准备好。

我目前的做法是，在malloc函数中分一次性获取所有的指针。然后确保在第一个calloc之前，至少调用一次malloc。

源码

核心库

/* gcc wrap_malloc.c -shared -o libwrap.so -ldl -fPIC */

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

#define __USE_GNU
#include <dlfcn.h>

static void* (*real_malloc)(size_t) = NULL;
static void* (*real_calloc)(size_t, size_t) = NULL;
static void* (*real_realloc)(void*, size_t) = NULL;

void* malloc(size_t size)
{
    if (real_malloc == NULL) {
        real_malloc = dlsym(RTLD_NEXT, "malloc");
    }
    if (real_calloc == NULL) {
        real_calloc = dlsym(RTLD_NEXT, "calloc");
    }
    if (real_realloc == NULL) {
        real_realloc = dlsym(RTLD_NEXT, "realloc");
    }

    void *p = NULL;
    char *e = getenv("NULL_MALLOC");
    if (e == NULL && real_malloc != NULL) {
        p = real_malloc(size);
    }
    return p;
}

void *calloc(size_t nmemb, size_t size)
{
    void *p = NULL;
    char *e = getenv("NULL_MALLOC");
    if (e == NULL && real_calloc != NULL) {
        p = real_calloc(nmemb, size);
    }
    return p;
}

void *realloc(void *ptr, size_t size)
{
    void *p = NULL;
    char *e = getenv("NULL_MALLOC");
    if (e == NULL && real_realloc != NULL) {
        p = real_realloc(ptr, size);
    }
    return p;
}

测试代码

/* g++ main.cpp -o test `pkg-config gtest gtest_main --cflags --libs` */

#include <stdlib.h>
#include <gtest/gtest.h>

TEST(malloc, normal)
{
    char *p = (char*)malloc(4);
    EXPECT_NE(p, (char*)NULL);
    free(p);

    setenv("NULL_MALLOC", "1", 1);
    p = (char*)malloc(4);
    unsetenv("NULL_MALLOC");
    EXPECT_EQ(p, (char*)NULL);

    p = (char*)malloc(4);
    EXPECT_NE(p, (char*)NULL);
    free(p);
}

TEST(calloc, normal)
{
    char *p = (char*)calloc(4, 4);
    EXPECT_NE(p, (char*)NULL);
    free(p);

    setenv("NULL_MALLOC", "1", 1);
    p = (char*)calloc(4, 4);
    unsetenv("NULL_MALLOC");
    EXPECT_EQ(p, (char*)NULL);

    p = (char*)calloc(4, 4);
    EXPECT_NE(p, (char*)NULL);
    free(p);
}

TEST(realloc, normal)
{
    char *p = (char*)malloc(4);
    EXPECT_NE(p, (char*)NULL);
    p = (char*)realloc(p, 10);
    EXPECT_NE(p, (char*)NULL);
    free(p);

    p = (char*)malloc(4);
    EXPECT_NE(p, (char*)NULL);
    setenv("NULL_MALLOC", "1", 1);
    p = (char*)realloc(p, 40);
    unsetenv("NULL_MALLOC");
    EXPECT_EQ(p, (char*)NULL);

    p = (char*)malloc(10);
    EXPECT_NE(p, (char*)NULL);
    p = (char*)realloc(p, 40);
    EXPECT_NE(p, (char*)NULL);
    free(p);
}

int main(int argc, char **argv)
{
    ::testing::InitGoogleTest(&argc, argv);
    ::testing::FLAGS_gtest_break_on_failure = false;

    return RUN_ALL_TESTS();
}

编译和运行：

gcc wrap_malloc.c -shared -o libwrap.so -ldl -fPIC
g++ main.cpp -o test `pkg-config gtest gtest_main --cflags --libs`
LD_PRELOAD=/path/to/libwrap.so ./test

参照：

替换 malloc 的方法

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