fdeclspec not enabled -- cLion Mac - c++

Question

I want to build a dll which can be used by any c++ and c# application can use. I installed cLion on mac and started a new project as c++ library.
I wrote some lines of code in the header file. Since I want to export my functions, I used __fdeclspec
But it is throwing me the error '__declspec' attributes are not enabled; use '-fdeclspec' or '-fms-extensions' to enable support for __declspec attributes
My code is
#pragma once
#ifdef MATHLIBRARY_EXPORTS
#define MATHLIBRARY_API __declspec(dllexport)
#else
#define MATHLIBRARY_API __declspec(dllimport)
#endif
extern "C" MATHLIBRARY_API void fibonacci_init(
const unsigned long long a, const unsigned long long b);
extern "C" MATHLIBRARY_API bool fibonacci_next();
extern "C" MATHLIBRARY_API unsigned long long fibonacci_current();
extern "C" MATHLIBRARY_API unsigned fibonacci_index();
How to fix this error so that I can build the solution?

Answer 1

You can use the following preprocessor checks to make a cross-platform macro for the export semantics:
#if defined(_MSC_VER)
#define MY_LIB_API __declspec(dllexport) // Microsoft
#elif defined(__GNUC__)
#define MY_LIB_API __attribute__((visibility("default"))) // GCC
#else
#define MY_LIB_API // Most compilers export all the symbols by default. We hope for the best here.
#pragma warning Unknown dynamic link import/export semantics.
#endif
So, in your code it would be:
#pragma once
#if defined(_MSC_VER)
#define MATHLIBRARY_API __declspec(dllexport) // Microsoft
#elif defined(__GNUC__)
#define MATHLIBRARY_API __attribute__((visibility("default"))) // GCC
#else
#define MATHLIBRARY_API // Most compilers export all the symbols by default. We hope for the best here.
#pragma warning Unknown dynamic link import/export semantics.
#endif
extern "C" MATHLIBRARY_API void fibonacci_init(
const unsigned long long a, const unsigned long long b);
extern "C" MATHLIBRARY_API bool fibonacci_next();
extern "C" MATHLIBRARY_API unsigned long long fibonacci_current();
extern "C" MATHLIBRARY_API unsigned fibonacci_index();