Allow double floating point comparisons with Unity unit testing framework from Throw The Switch

I'm having some trouble somewhere with the linker while trying to compile a test written using the Unity testing framework by Throw The Switch. I have other tests that compile and run perfectly fine so I'm definitely just missing something in enabling the assertion helper for double floating point comparisons.

There is documentation in the header file telling us how to enable double floating point comparisons.

 *     - define UNITY_INCLUDE_DOUBLE to allow double floating point comparisons

However, I end up with this error:

Undefined symbols for architecture x86_64:
  "_UnityAssertDoublesWithin", referenced from:
      _test_example in main-6fae82.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

I wrote up the simplest example possible to duplicate this:

#define UNITY_INCLUDE_DOUBLE

#include "unity.h"

void test_example(void)
{
    TEST_ASSERT_EQUAL_DOUBLE(1.234, 1.234);
}

int main(void) {
    UNITY_BEGIN();
    RUN_TEST(test_example);
    return UNITY_END();
}

The contents of the CWD of the example and the exact command used to call clang (showing the same error again):

$ ls
main.c          unity.c         unity.h         unity_internals.h
$ clang unity.c main.c
Undefined symbols for architecture x86_64:
  "_UnityAssertDoublesWithin", referenced from:
      _test_example in main-ee77c2.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Same exact thing happens with gcc (but it's actually just calling clang under the hood).

I'm pretty sure I'm just missing one tiny step but for the life of me I can't see what it is right now. Thanks in advance for your help.

Solution

I have this working on my minimal tests by using the same define in the unity_config.h file and adding UNITY_INCLUDE_CONFIG_H as a compiler -D flag (gcc). But running with the #define in the source does not do the same trick

You can find a full copy of a unity_config.h file on the ThrowTheSwitch GitHub repo. I usually just throw it in the same folder Unity is in.

It also works if you add the define directly into the unity.h file as specified in the comments in that file (that you quote in your question) which says

All options described below should be passed as a compiler flag to all files using Unity. If you must add #defines, place them BEFORE the #include above.

i.e. in unity.h

#define UNITY_INCLUDE_DOUBLE
#include "unity_internals.h"
...

Why your initial tactic, which should essentially be the same thing, does not work, I do not know.