GLFWAPI is used to declare public API functions for export from the DLL / shared library/ dynamic library.
/* We are building GLFW as a Win32 DLL. */
#define GLFWAPI __declspec(dllexport)
/* We are calling GLFW as a Win32 DLL. */
#define GLFWAPI __declspec(dllimport)
/* We are building GLFW as a shared / dynamic library. */
#define GLFWAPI __attribute__((visibility(“default”)))
/* We are building or calling GLFW as a static library. */