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author卜部昌平 <shyouhei@ruby-lang.org>2020-04-10 14:11:40 +0900
committer卜部昌平 <shyouhei@ruby-lang.org>2020-04-13 16:06:00 +0900
commit4ff3f205408ff8bb413d69151105d301858136ba (patch)
tree0494fea3f4cdb82ec1d34e462438389dfea8b8da /include/ruby/backward/cxxanyargs.hpp
parenta3f6f67967644f34226b4424227d2eec52fedd45 (diff)
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
Notes
Notes: Merged: https://github.com/ruby/ruby/pull/3023
Diffstat (limited to 'include/ruby/backward/cxxanyargs.hpp')
-rw-r--r--include/ruby/backward/cxxanyargs.hpp5
1 files changed, 2 insertions, 3 deletions
diff --git a/include/ruby/backward/cxxanyargs.hpp b/include/ruby/backward/cxxanyargs.hpp
index 8fda5fe906..c30ab46f43 100644
--- a/include/ruby/backward/cxxanyargs.hpp
+++ b/include/ruby/backward/cxxanyargs.hpp
@@ -1,4 +1,5 @@
-/// \noop-*-C++-*-vi:ft=cpp
+#ifndef RUBY_BACKWARD_CXXANYARGS_HPP //-*-C++-*-vi:ft=cpp
+#define RUBY_BACKWARD_CXXANYARGS_HPP
/// @file
/// @author \@shyouhei
/// @copyright This file is a part of the programming language Ruby.
@@ -9,8 +10,6 @@
/// meant to be a backwards compatibility shim. Please stick to
/// C++ 98 and never use newer features, like `constexpr`.
/// @brief Provides old prototypes for C++ programs.
-#ifndef RUBY_BACKWARD_CXXANYARGS_HPP
-#define RUBY_BACKWARD_CXXANYARGS_HPP
#include "ruby/3/config.h"
#include "ruby/3/intern/class.h"
#include "ruby/3/intern/cont.h"