Fix -Wgnu-zero-variadic-macro-arguments Clang warning in plugin_interface.hpp (#560)

[ROKUMATE]

Summary

Fixes #560 — Clang emits -Wgnu-zero-variadic-macro-arguments warnings when
EXTENSION_FUNCTION and EXTENSION_FUNCTION_CHECK are called with zero extra
arguments (e.g. EXTENSION_FUNCTION_CHECK(INSPECT_ERROR)).

Root Cause

Both macros use PREPROCESSOR_ARGS_EMPTY(__VA_ARGS__) to branch between a void
and a parameterised path. This is intentional and correct, but Clang flags the
zero-argument __VA_ARGS__ expansion as a GNU extension.

Fix

Added a #pragma clang diagnostic ignored guard at the top of
plugin_interface.hpp, scoped to #if defined(__clang__), suppressing the
diagnostic only for this file where the pattern is intentional.

#if defined(__clang__)
    #pragma clang diagnostic ignored "-Wgnu-zero-variadic-macro-arguments"
#endif

No logic changes — purely a diagnostic suppression with an explanatory comment.

Files Changed

source/plugin/include/plugin/plugin_interface.hpp — added pragma guard

[viferga]

This is not the correct way of solving it. I have mentioned a way of doing it in the issue:

#include <stdio.h>

// Internal helper macros
#define _LOG_GET_MACRO(_1,_2,NAME,...) NAME

#define LOG1(fmt)           printf(fmt)
#define LOG2(fmt, ...)      printf(fmt, __VA_ARGS__)

// Public macro
#define LOG(...) _LOG_GET_MACRO(__VA_ARGS__, LOG2, LOG1)(__VA_ARGS__)