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author | 卜部昌平 <shyouhei@ruby-lang.org> | 2020-04-10 14:11:40 +0900 |
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committer | 卜部昌平 <shyouhei@ruby-lang.org> | 2020-04-13 16:06:00 +0900 |
commit | 4ff3f205408ff8bb413d69151105d301858136ba (patch) | |
tree | 0494fea3f4cdb82ec1d34e462438389dfea8b8da /vm_debug.h | |
parent | a3f6f67967644f34226b4424227d2eec52fedd45 (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 'vm_debug.h')
-rw-r--r-- | vm_debug.h | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/vm_debug.h b/vm_debug.h index 8e0350d147..93ee2e4297 100644 --- a/vm_debug.h +++ b/vm_debug.h @@ -1,3 +1,5 @@ +#ifndef RUBY_DEBUG_H +#define RUBY_DEBUG_H /********************************************************************** vm_debug.h - YARV Debug function interface @@ -9,9 +11,6 @@ **********************************************************************/ -#ifndef RUBY_DEBUG_H -#define RUBY_DEBUG_H - #include "ruby/ruby.h" #include "node.h" |