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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 |
| commit | 4ff3f205408ff8bb413d69151105d301858136ba (patch) | |
| tree | 0494fea3f4cdb82ec1d34e462438389dfea8b8da /constant.h | |
| parent | a3f6f67967644f34226b4424227d2eec52fedd45 (diff) | |
| download | ruby-4ff3f205408ff8bb413d69151105d301858136ba.tar.gz | |
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
Diffstat (limited to 'constant.h')
| -rw-r--r-- | constant.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/constant.h b/constant.h index 1396651e21..e0d36909e1 100644 --- a/constant.h +++ b/constant.h @@ -1,3 +1,5 @@ +#ifndef CONSTANT_H +#define CONSTANT_H /********************************************************************** constant.h - @@ -8,8 +10,6 @@ Copyright (C) 2009 Yusuke Endoh **********************************************************************/ -#ifndef CONSTANT_H -#define CONSTANT_H #include "ruby/ruby.h" #include "id_table.h" |