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
r33876. [ruby-core:41475] [Bug #5706]
* ext/socket/extconf.rb: the alternative hack for [Bug #5675].
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@33947 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
calls with zero arguments can be substituted. aliasing in .def
file has no effect for static library. [ruby-core:41370]
[Bug#5681]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@33916 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* include/ruby/missing.h: don't substitute "close", etc. here.
* include/ruby/ruby.h: include ruby/subst.h at last.
This prevents substituting "close" in unitstd.h.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@28907 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
