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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 /vm_opts.h
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 'vm_opts.h')
-rw-r--r--vm_opts.h7
1 files changed, 2 insertions, 5 deletions
diff --git a/vm_opts.h b/vm_opts.h
index 3df9ce837b..02d60e71fd 100644
--- a/vm_opts.h
+++ b/vm_opts.h
@@ -1,4 +1,5 @@
-/*-*-c-*-*/
+#ifndef RUBY_VM_OPTS_H/*-*-c-*-*/
+#define RUBY_VM_OPTS_H
/**********************************************************************
vm_opts.h - VM optimize option
@@ -9,10 +10,6 @@
**********************************************************************/
-
-#ifndef RUBY_VM_OPTS_H
-#define RUBY_VM_OPTS_H
-
/* Compile options.
* You can change these options at runtime by VM::CompileOption.
* Following definitions are default values.