Objective–C++ tests using OCMock fail to link

[danyowdee]

Issue

When using OCMock in Objective–C++ test classes, linking the tests fails under certain circumstances with an error like the following:

Undefined symbols for architecture x86_64:
  "OCMMakeLocation(objc_object*, char const*, int)", referenced from:
      -[D12AwesomenessTests testThatObjCxxWithOCMockIsAwesome] in D12AwesomenessTests.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

The reason for this is simple and can be found in <OCMock/OCMMakeLocation.h>:
extern OCMLocation *OCMMakeLocation(id testCase, const char *file, int line);

This function is declared extern, but not extern "C" as it would need to.

Foundation and the other Apple frameworks solve this by defining a macro like the following:

// From <Foundation/NSObjCRuntime.h>
#if defined(__cplusplus)
#define FOUNDATION_EXTERN extern "C"
#else
#define FOUNDATION_EXTERN extern
#endif

And all exported C functions are subsequently declared this way.

Motivation

As you’re well aware of, Swift is somewhat hostile to mocking. On the C++’s auto keyword, on the other hand, significantly reduces the amount of boilerplate you have to write in an “Objective–C Generics” world.
So using Objective–C++ for tests with OCMock seem like a perfect match; in theory.

In practice, not reliably being able to link your tests depending on inclusion order or something like that is a bit of a downer.

[erikdoe]

Merged #239 now and refactored to using macro as suggested here.

[danyowdee]

Thanks for pulling, even after you went the more exhausted route!

I considered the macro wasn't worth it because I only saw this one public function, but it sure does read nicer that way. Sorry for the inconvenience this caused!