From 4ff3f205408ff8bb413d69151105d301858136ba Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E5=8D=9C=E9=83=A8=E6=98=8C=E5=B9=B3?= Date: Fri, 10 Apr 2020 14:11:40 +0900 Subject: add #include guard hack According to MSVC manual (*1), cl.exe can skip including a header file when that: - contains #pragma once, or - starts with #ifndef, or - starts with #if ! defined. GCC has a similar trick (*2), but it acts more stricter (e. g. there must be _no tokens_ outside of #ifndef...#endif). Sun C lacked #pragma once for a looong time. Oracle Developer Studio 12.5 finally implemented it, but we cannot assume such recent version. This changeset modifies header files so that each of them include strictly one #ifndef...#endif. I believe this is the most portable way to trigger compiler optimizations. [Bug #16770] *1: https://docs.microsoft.com/en-us/cpp/preprocessor/once *2: https://gcc.gnu.org/onlinedocs/cppinternals/Guard-Macros.html --- include/ruby/3/has/cpp_attribute.h | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) (limited to 'include/ruby/3/has/cpp_attribute.h') diff --git a/include/ruby/3/has/cpp_attribute.h b/include/ruby/3/has/cpp_attribute.h index 70bec4a267..42209c0955 100644 --- a/include/ruby/3/has/cpp_attribute.h +++ b/include/ruby/3/has/cpp_attribute.h @@ -1,4 +1,6 @@ -/** \noop-*-C++-*-vi:ft=cpp +#ifndef RUBY3_HAS_CPP_ATTRIBUTE_H /*-*-C++-*-vi:se ft=cpp:*/ +#define RUBY3_HAS_CPP_ATTRIBUTE_H +/** * @file * @author Ruby developers * @copyright This file is a part of the programming language Ruby. @@ -21,10 +23,7 @@ #include "ruby/3/compiler_is.h" /** @cond INTERNAL_MACRO */ -#if defined(RUBY3_HAS_CPP_ATTRIBUTE0) -# /* Take that. */ - -#elif defined(__has_cpp_attribute) +#if defined(__has_cpp_attribute) # define RUBY3_HAS_CPP_ATTRIBUTE0(_) __has_cpp_attribute(_) #elif RUBY3_COMPILER_IS(MSVC) @@ -66,15 +65,13 @@ /** @endcond */ /** Wraps (or simulates) `__has_cpp_attribute`. */ -#ifdef RUBY3_HAS_CPP_ATTRIBUTE -# /* Take that. */ - -#elif ! defined(__cplusplus) +#if ! defined(__cplusplus) # /* Makes no sense. */ # define RUBY3_HAS_CPP_ATTRIBUTE(_) 0 - #else # /* GCC needs workarounds. See https://gcc.godbolt.org/z/jdz3pa */ # define RUBY3_HAS_CPP_ATTRIBUTE(_) \ ((RUBY3_HAS_CPP_ATTRIBUTE0(_) <= __cplusplus) ? RUBY3_HAS_CPP_ATTRIBUTE0(_) : 0) #endif + +#endif /* RUBY3_HAS_CPP_ATTRIBUTE_H */ -- cgit v1.2.3