I have a source and header file like this:

FileA.h

...
//#define X_TESTMODE // --> If I set X_TESTMODE here, GTest can call the function foo()

#ifndef X_TESTMODE
    #define X_STATIC static
#else
    #define X_STATIC
#endif
...

FileA.c

...
X_STATIC uint8 foo(...)
{
    ...
}
...

In GTest, I want to set X_TESTMODE to make the static function visible for testing purposes.

ut_FileA.cc

...
extern "C" {

    #define X_TESTMODE // --> This doesn't work and foo() is not visible in GTest

    #include FileA.h

    extern uint8 foo(...);
}

#define X_TESTMODE // --> This doesn't work and foo() is not visible in GTest
...
TEST(Test, foo){
    ...
    uint8 x = foo(...);
    ...
}

If I set X_TESTMODE in FileA.h, GTest can see the foo() function, but if I set it in the GTest file ut_FileA.cc, then the foo() function is not visible.

X_TESTMODE must be set in ut_FileA.cc.

Does anyone have an idea?