Remove consts from defined structs to avoid errors with c++

[sebirdman]

This should properly resolve #51

[AppVeyorBot]

❌ Build fff 85-appveyor failed (commit b27f8d19ad by @sebirdman)

[AppVeyorBot]

❌ Build fff 86-appveyor failed (commit 6fb172869f by @sebirdman)

[sebirdman]

I'm not sure what the tests are doing exactly, i'm not able to reproduce these failures on my machine

[johwech]

The changes introduced by the original pull request require the fff.h to be not included within an extern "C" block when compiling with a cpp compiler.

I fixed the issue by wrapping an additional extern "C++" block around the whole fff.h:
https://ci.appveyor.com/project/johwech/fff/builds/32597466

Alternatively it's also possible to just fix the test and tell the users that fff.h cannot be included within an extern "C" segment when a CPP compiler is used:
https://ci.appveyor.com/project/johwech/fff/builds/32597324

[gndl]

Hi,
first of all thank you for this great tool.
This PR allows me to use FFF, how can I help to get it integrated mainstream?

[leonardopsantos]

This feature would be great, but unfortunately the seems abandoned. There's a very ugly workaround that works for C++ compilers. Say that you want to test int foo(int a, const int b). In your test code, you can do:

foo.cpp:

bool foo(int a, const int b)
{
    ...
}

foo.hpp:

bool foo(int a, const int b);

test_foo.cpp:

#include <gtest/gtest.h>
#include <fff.h>

#include "foo.hpp"

DEFINE_FFF_GLOBALS;

extern "C" {

/**
 * Fakes
 */

FAKE_VALUE_FUNC(bool, __foo, int, int);

} // extern "C"

// Re-implementation of foo using linker-seam
// Must keep const-ness
bool foo(int a, const int b)
{
    // Call "actual fake"
    return __foo(a, (int) b);  // Need to use C-style casts to remove constness
}

Use __foo_fake normally, with RESET_FAKE(__foo), ASSERT_EQ(__foo_fake.call_count, 1);