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Macros
#define	RCUTILS_IMPORT __attribute__ ((visibility("default")))

#define	RCUTILS_EXPORT __attribute__ ((visibility("default")))

#define	RCUTILS_LOCAL __attribute__ ((visibility("hidden")))

Macro Definition Documentation

◆ RCUTILS_IMPORT

#define RCUTILS_IMPORT __attribute__ ((visibility("default")))

Defines macros to express whether a symbol is localed, imported, or exported

Those macros are compatible with GCC, clang, and Microsoft Visual C++. They can be used to enforce which symbols of a library are publicly accessible.

RCUTILS_IMPORT, RCUTILS_EXPORT, and RCUTILS_LOCAL are respectively declaring an imported, exported, or local symbol. RCUTILS_LOCAL can be used directly. However, RCUTILS_IMPORT, and RCUTILS_EXPORT may not be used directly. Every project need to provide an additional header called visibility_macros.h containing:

#ifdef <project>_BUILDING_DLL

define <project>_PUBLIC RCUTILS_EXPORT

#else

define <project>_PUBLIC RCUTILS_IMPORT

#endif // !<project>_BUILDING_DLL #define <project>_LOCAL RCUTILS_LOCAL

...where "<project>" has been replaced by the project name, such as "MY_PROJECT". Your project CMakeLists.txt should also contain the following statement:

target_compile_definitions(<your library> PRIVATE "<project>_BUILDING_DLL")

A public (exported) class should then be tagged as <project>_PUBLIC, whereas a non-public class should be tagged with <project>_LOCAL.

See GCC documentation: https://gcc.gnu.org/wiki/Visibility

◆ RCUTILS_EXPORT

#define RCUTILS_EXPORT __attribute__ ((visibility("default")))

◆ RCUTILS_LOCAL

#define RCUTILS_LOCAL __attribute__ ((visibility("hidden")))