multiple definition of global with gmock-global in unit testing - c++

Question

I am trying to mock global function using https://github.com/apriorit/gmock-global library.
Note: this description contains example of the real scenario not the exact real scenario. Also I am not allowed to make any changes to global.hpp.
My example dir structure looks like below
--src
------global.hpp
------classA.hpp
------classB.hpp
------main.cpp
--ut
------classATests.cpp
------classBTests.cpp
------main.cpp
The ut/main.cpp tests testcases in classATests.cpp and classBTests.cpp.
global.hpp contains a global function
int giveIndex()
{
return 1;
}
classA.hpp calls giveIndex() global function
#include "global.hpp"
class A
{
public:
int checkIndex() { return giveIndex(); };
}
classB.hpp calls giveIndex() global function
#include "global.hpp"
class B
{
public:
int checkIndex() { return giveIndex(); };
}
classATests.cpp contains
#include <memory>
#include <gtest/gtest.h>
#include <gmock/gmock.h>
#include <gmock-global/gmock-global.h>
#include "src/classA.hpp"
MOCK_GLOBAL_FUNC0(giveIndex, int(void));
using namespace ::testing
struct classATests : public ::testing::Test
{
void Setup() override
{
sut_ = std::make_shared<A>();
}
std::shared_ptr<A> sut_;
};
TEST_F(classATests , checkIndex)
{
EXPECT_GLOBAL_CALL(giveIndex, giveIndex()).WillOnce(Return(1));
sut_->checkIndex();
}
classBTests.cpp contains
#include <memory>
#include <gtest/gtest.h>
#include <gmock/gmock.h>
#include <gmock-global/gmock-global.h>
#include "src/classB.hpp"
MOCK_GLOBAL_FUNC0(giveIndex, int(void));
using namespace ::testing
struct classBTests : public ::testing::Test
{
void Setup() override
{
sut_ = std::make_shared<B>();
}
std::shared_ptr<B> sut_;
};
TEST_F(classBTests , checkIndex)
{
EXPECT_GLOBAL_CALL(giveIndex, giveIndex()).WillOnce(Return(1));
sut_->checkIndex();
}
The issue now is when i compile and run UT for both classATests.cpp and classBTests.cpp i get errors saying
... multiple definition of 'giveIndex' ;
and
... multiple definitions of gmock_globalmock_giveIndex_instance
Is there any way to avoid this issue ? classA tests and classB tests need to be in 2 different files like it is now.

Answer 1

Functions defined in header files should be defined inline
inline int giveIndex()
{
return 1;
}
otherwise you will get multiple definition errors if you include the header file more than once.
The alternative would be to only declare the function in your header file
int giveIndex();
and then define it (but not inline) in one of your cpp files.
This is the normal way to organise C++ code. gmock has nothing to do with this.