C中的函数模拟(用于测试)? [英] Function mocking (for testing) in C?

问题描述

我想用 C 语言为 C 库编写测试.我想模拟出一些用于测试的函数.

I would like to write tests for a C library, in C. I'd like to mock out some functions for the test.

假设我的库是从以下来源编译的:

Suppose my library is compiled from the following source:

/* foo.h */
int myfunction(int x, int y);

/* foo.c */
#include "foo.h"

static int square(int x) { return x * x; }

int myfunction(int x, int y) {
    return square(x) + square(y);
}

我想写一个这样的测试:

I want to write a test like this:

/* foo_test.c */
#include "foo.h"

static int square(int x) { return x + 1; }

int main(void) {
    assert(myfunction(0, 0) == 2);
    return 0;
}

有什么方法可以编译，以便 myfunction 将使用 foo_test.c 中的 square 定义，而不是foo.c，仅在链接可执行文件foo_test时?也就是我想把foo.c编译成一个库(姑且称之为libfoo.so)，然后用foo_test.c编译libfoo.so 和一些魔法，这样我就可以得到一个可执行的 foo_test，它使用 square 的不同实现.

Is there any way I can compile so that myfunction will use the definition of square in foo_test.c, instead of the one in foo.c, only when linking the executable foo_test? That is, I want to compile foo.c into a library (let's call it libfoo.so), and then compile foo_test.c with libfoo.so and some magic so that I'll get an executable foo_test which uses the different implementation of square.

当 square 没有声明为 static 时，听听解决方案会很有帮助，但解决上述情况会更好.

It would be helpful to hear solutions for when square is not declared static, but solving the above case would be even better.

似乎没有希望，但这里有一个想法:假设我用 -O0 -g 编译，所以 square 不太可能被内联，我应该有符号显示呼叫解决的地方.有没有办法潜入目标文件并换出已解析的引用?

It seems hopeless, but here's an idea: Suppose I compile with -O0 -g so it's unlikely that square will get inlined and I should have symbols showing where the call was resolved. Is there a way to sneak into the object file and swap out the resolved reference?

推荐答案

看来你使用的是GCC，所以可以使用weak属性:

It looks like you are using GCC, so you can use the weak attribute:

weak 属性导致声明被作为弱符号而不是全局.这主要用于定义可以在用户代码中覆盖的库函数，尽管它可以也可用于非函数声明.弱符号是支持 ELF 目标，并且在使用GNU 汇编器和链接器.

The weak attribute causes the declaration to be emitted as a weak symbol rather than a global. This is primarily useful in defining library functions which can be overridden in user code, though it can also be used with non-function declarations. Weak symbols are supported for ELF targets, and also for a.out targets when using the GNU assembler and linker.

http://gcc.gnu.org/onlinedocs/gcc/Function-属性.html

这篇关于C中的函数模拟(用于测试)?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！