OCMock 3.0.2链接器错误，带.mm测试文件 [英] OCMock 3.0.2 linker error with .mm test file

问题描述

我使用OCMock 3.0.2，我通过cocoapods为我的测试目标安装：

I am using OCMock 3.0.2, which I've installed through cocoapods for my test target:

platform :ios, '7.0'
xcodeproj 'myProject.xcodeproj'

target :myTestTarget do
  pod 'OCMock', '~> 3.0.2'
end

link_with "myTestTarget"

在我的测试文件（myTest.mm）中，我已经包括OCMock，并想要尝试新的验证就地策略，如下：

In my test file (myTest.mm), I've included OCMock and want to try out the new verify-in-place strategy, like so:

- (void) test_myTest
{
    MyObject *obj = [MyObject new];
    id robotMock = OCMPartialMock(obj);

    [obj testMethod];

    // some asserts
    OCMVerify([obj _internalMethodToBeCalled]);
}

到目前为止似乎正常。但是，当我试图运行这个特定的测试用例，我得到链接器错误：

So far seems normal. However, when I tried to run this specific test case, I am getting linker error:

Undefined symbols for architecture i386:
  "OCMMakeLocation(objc_object*, char const*, int)", referenced from:
      -[MyTests test_myTest] in MyTests.o
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)

I验证OCMock被正确拉入，OCMLocation.h / m文件也被引用。我看到OCMMakeLocation似乎是一个extern函数，但是.m文件作为一个依赖项目在我的pods构建目标，但不知何故，它没有被链接。我必须让我的测试是.mm，因为我包括一些c ++文件。为什么会是OCMock的问题？

I verified that OCMock was pulled in correctly and OCMLocation.h/m files are referenced too. I see that OCMMakeLocation seems to be an extern function but the .m file is there as a dependent project in my pods build target, but somehow it is not being linked. I have to make my test to be .mm since I am including some c++ files. Why would this be the problem for OCMock?

推荐答案

OCMMakeLocation声明如下

OCMMakeLocation is declared like this

OCMLocation.h：

OCMLocation.h:

extern OCMLocation *OCMMakeLocation(id testCase, const char *file, int line);

OCMLocation.m：

OCMLocation.m:

OCMLocation *OCMMakeLocation(id testCase, const char *fileCString, int line)
{
    return [OCMLocation locationWithTestCase:testCase file:[NSString stringWithUTF8String:fileCString] line:line];
}

这是一个在Objective-C接口之外定义的直接C函数。我不知道编译器实际上在做什么（也许别人可以解释它更好），但为了我的理解，这是发生了什么：你的测试文件是一个Objective-C ++文件，所以它得到遵循C ++链接，这是名称调整（请参阅名称调整）。但是，OCMLocation被编译为一个Objective-C文件，所以它获得C链接，而不是C ++链接，所以没有名称调整。因为你的测试符合C ++链接，它拉入OCMock.h并假定它也是一个C ++头文件，所以它假设编译它的源的结果将是相同的，这不会是。

It's a straight C function defined outside of the Objective-C interface. I'm not knowledgeable enough about what the complier is actually doing (maybe someone else can explain it better), but to the best of my understanding, this is what's going on: Your test file is an Objective-C++ file, so it's getting complied with C++ linkage, which does name mangling (see this about name mangling). However, OCMLocation is compiled as a Objective-C file, so it gets C linkage, not C++ linkage, so no name mangling. Because your test is complied with C++ linkage, it pulls in OCMock.h and assumes it's also a C++ header, so it assumes the result of compiling it's source will be the same, which it's not going to be.

为了解决这个问题，所有你需要做的是告诉编译器OCMock.h是一个C头在你的测试文件：

Long story short, to fix this, all you need to do is tell the compiler that OCMock.h is a C header in your test file:

#ifdef __cplusplus
extern "C" {
#endif
#import <OCMock/OCMock.h>
#ifdef __cplusplus
}
#endif

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