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

13 files changed, 39 insertions, 39 deletions

diff --git a/include/ruby/3/core/rarray.h b/include/ruby/3/core/rarray.h
index cd8767a8a8..3234daae90 100644
--- a/include/ruby/3/core/rarray.h
+++ b/include/ruby/3/core/rarray.h
@@ -1,4 +1,6 @@
-/**                                                     \noop-*-C++-*-vi:ft=cpp
+#ifndef RUBY3_RARRAY_H                               /*-*-C++-*-vi:se ft=cpp:*/
+#define RUBY3_RARRAY_H
+/**
  * @file
  * @author     Ruby developers <ruby-core@ruby-lang.org>
  * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
@@ -18,8 +20,6 @@
  *             extension libraries. They could be written in C++98.
  * @brief      Defines struct ::RArray.
  */
-#ifndef  RUBY3_RARRAY_H
-#define  RUBY3_RARRAY_H
 #include "ruby/3/arithmetic/long.h"
 #include "ruby/3/attr/artificial.h"
 #include "ruby/3/attr/constexpr.h"
diff --git a/include/ruby/3/core/rbasic.h b/include/ruby/3/core/rbasic.h
index 510dd38da6..4f6fa576aa 100644
--- a/include/ruby/3/core/rbasic.h
+++ b/include/ruby/3/core/rbasic.h
@@ -1,4 +1,6 @@
-/**                                                     \noop-*-C++-*-vi:ft=cpp
+#ifndef RUBY3_RBASIC_H                               /*-*-C++-*-vi:se ft=cpp:*/
+#define RUBY3_RBASIC_H
+/**
  * @file
  * @author     Ruby developers <ruby-core@ruby-lang.org>
  * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
@@ -18,8 +20,6 @@
  *             extension libraries. They could be written in C++98.
  * @brief      Defines struct ::RBasic.
  */
-#ifndef  RUBY3_RBASIC_H
-#define  RUBY3_RBASIC_H
 #include "ruby/3/attr/artificial.h"
 #include "ruby/3/attr/constexpr.h"
 #include "ruby/3/attr/forceinline.h"
diff --git a/include/ruby/3/core/rbignum.h b/include/ruby/3/core/rbignum.h
index c1183e3ea6..09a478c2f8 100644
--- a/include/ruby/3/core/rbignum.h
+++ b/include/ruby/3/core/rbignum.h
@@ -1,4 +1,6 @@
-/**                                                     \noop-*-C++-*-vi:ft=cpp
+#ifndef RUBY3_RBIGNUM_H                              /*-*-C++-*-vi:se ft=cpp:*/
+#define RUBY3_RBIGNUM_H
+/**
  * @file
  * @author     Ruby developers <ruby-core@ruby-lang.org>
  * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
@@ -18,8 +20,6 @@
  *             extension libraries. They could be written in C++98.
  * @brief      Routines to manipulate struct ::RBignum.
  */
-#ifndef  RUBY3_RBIGNUM_H
-#define  RUBY3_RBIGNUM_H
 #include "ruby/3/dllexport.h"
 #include "ruby/3/value.h"
 #include "ruby/3/value_type.h"
diff --git a/include/ruby/3/core/rclass.h b/include/ruby/3/core/rclass.h
index a54b34f5ba..e492da5ae5 100644
--- a/include/ruby/3/core/rclass.h
+++ b/include/ruby/3/core/rclass.h
@@ -1,4 +1,6 @@
-/**                                                     \noop-*-C++-*-vi:ft=cpp
+#ifndef RUBY3_RCLASS_H                               /*-*-C++-*-vi:se ft=cpp:*/
+#define RUBY3_RCLASS_H
+/**
  * @file
  * @author     Ruby developers <ruby-core@ruby-lang.org>
  * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
@@ -18,8 +20,6 @@
  *             extension libraries. They could be written in C++98.
  * @brief      Routines to manipulate struct ::RClass.
  */
-#ifndef  RUBY3_RCLASS_H
-#define  RUBY3_RCLASS_H
 #include "ruby/3/dllexport.h"
 #include "ruby/3/value.h"
 #include "ruby/3/cast.h"
diff --git a/include/ruby/3/core/rdata.h b/include/ruby/3/core/rdata.h
index 651ceed0d7..6df6ea9e6d 100644
--- a/include/ruby/3/core/rdata.h
+++ b/include/ruby/3/core/rdata.h
@@ -1,4 +1,6 @@
-/**                                                     \noop-*-C++-*-vi:ft=cpp
+#ifndef RUBY3_RDATA_H                                /*-*-C++-*-vi:se ft=cpp:*/
+#define RUBY3_RDATA_H
+/**
  * @file
  * @author     Ruby developers <ruby-core@ruby-lang.org>
  * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
@@ -18,8 +20,6 @@
  *             extension libraries. They could be written in C++98.
  * @brief      Defines struct ::RData.
  */
-#ifndef  RUBY3_RDATA_H
-#define  RUBY3_RDATA_H
 #include "ruby/3/config.h"
 
 #ifdef STDC_HEADERS
diff --git a/include/ruby/3/core/rfile.h b/include/ruby/3/core/rfile.h
index 2b80a96e40..0b12d7bba4 100644
--- a/include/ruby/3/core/rfile.h
+++ b/include/ruby/3/core/rfile.h
@@ -1,4 +1,6 @@
-/**                                                     \noop-*-C++-*-vi:ft=cpp
+#ifndef RUBY3_RFILE_H                                /*-*-C++-*-vi:se ft=cpp:*/
+#define RUBY3_RFILE_H
+/**
  * @file
  * @author     Ruby developers <ruby-core@ruby-lang.org>
  * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
@@ -18,8 +20,6 @@
  *             extension libraries. They could be written in C++98.
  * @brief      Defines struct ::RFile.
  */
-#ifndef  RUBY3_RFILE_H
-#define  RUBY3_RFILE_H
 #include "ruby/3/core/rbasic.h"
 #include "ruby/3/cast.h"
 
diff --git a/include/ruby/3/core/rhash.h b/include/ruby/3/core/rhash.h
index 3778130141..e8f9901aa5 100644
--- a/include/ruby/3/core/rhash.h
+++ b/include/ruby/3/core/rhash.h
@@ -1,4 +1,6 @@
-/**                                                     \noop-*-C++-*-vi:ft=cpp
+#ifndef RUBY3_RHASH_H                                /*-*-C++-*-vi:se ft=cpp:*/
+#define RUBY3_RHASH_H
+/**
  * @file
  * @author     Ruby developers <ruby-core@ruby-lang.org>
  * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
@@ -30,8 +32,6 @@
  *
  * Shyouhei stopped thinking.  Let them be as is.
  */
-#ifndef  RUBY3_RHASH_H
-#define  RUBY3_RHASH_H
 #include "ruby/3/config.h"
 
 #ifdef STDC_HEADERS
diff --git a/include/ruby/3/core/rmatch.h b/include/ruby/3/core/rmatch.h
index fff62f1473..f89cea849c 100644
--- a/include/ruby/3/core/rmatch.h
+++ b/include/ruby/3/core/rmatch.h
@@ -1,4 +1,6 @@
-/**                                                     \noop-*-C++-*-vi:ft=cpp
+#ifndef RUBY3_RMATCH_H                               /*-*-C++-*-vi:se ft=cpp:*/
+#define RUBY3_RMATCH_H
+/**
  * @file
  * @author     Ruby developers <ruby-core@ruby-lang.org>
  * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
@@ -18,8 +20,6 @@
  *             extension libraries. They could be written in C++98.
  * @brief      Defines struct ::RMatch.
  */
-#ifndef  RUBY3_RMATCH_H
-#define  RUBY3_RMATCH_H
 #include "ruby/3/attr/artificial.h"
 #include "ruby/3/attr/pure.h"
 #include "ruby/3/attr/returns_nonnull.h"
diff --git a/include/ruby/3/core/robject.h b/include/ruby/3/core/robject.h
index 82887a8c51..3f298214a9 100644
--- a/include/ruby/3/core/robject.h
+++ b/include/ruby/3/core/robject.h
@@ -1,4 +1,6 @@
-/**                                                     \noop-*-C++-*-vi:ft=cpp
+#ifndef RUBY3_ROBJECT_H                              /*-*-C++-*-vi:se ft=cpp:*/
+#define RUBY3_ROBJECT_H
+/**
  * @file
  * @author     Ruby developers <ruby-core@ruby-lang.org>
  * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
@@ -18,8 +20,6 @@
  *             extension libraries. They could be written in C++98.
  * @brief      Defines struct ::RObject.
  */
-#ifndef  RUBY3_ROBJECT_H
-#define  RUBY3_ROBJECT_H
 #include "ruby/3/config.h"
 
 #ifdef HAVE_STDINT_H
diff --git a/include/ruby/3/core/rregexp.h b/include/ruby/3/core/rregexp.h
index 1f30808e8a..0978c00c74 100644
--- a/include/ruby/3/core/rregexp.h
+++ b/include/ruby/3/core/rregexp.h
@@ -1,4 +1,6 @@
-/**                                                     \noop-*-C++-*-vi:ft=cpp
+#ifndef RUBY3_RREGEXP_H                              /*-*-C++-*-vi:se ft=cpp:*/
+#define RUBY3_RREGEXP_H
+/**
  * @file
  * @author     Ruby developers <ruby-core@ruby-lang.org>
  * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
@@ -18,8 +20,6 @@
  *             extension libraries. They could be written in C++98.
  * @brief      Defines struct ::RRegexp.
  */
-#ifndef  RUBY3_RREGEXP_H
-#define  RUBY3_RREGEXP_H
 #include "ruby/3/attr/artificial.h"
 #include "ruby/3/attr/pure.h"
 #include "ruby/3/cast.h"
diff --git a/include/ruby/3/core/rstring.h b/include/ruby/3/core/rstring.h
index 244b90e96c..8951dd0d30 100644
--- a/include/ruby/3/core/rstring.h
+++ b/include/ruby/3/core/rstring.h
@@ -1,4 +1,6 @@
-/**                                                     \noop-*-C++-*-vi:ft=cpp
+#ifndef RUBY3_RSTRING_H                              /*-*-C++-*-vi:se ft=cpp:*/
+#define RUBY3_RSTRING_H
+/**
  * @file
  * @author     Ruby developers <ruby-core@ruby-lang.org>
  * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
@@ -18,8 +20,6 @@
  *             extension libraries. They could be written in C++98.
  * @brief      Defines struct ::RString.
  */
-#ifndef  RUBY3_RSTRING_H
-#define  RUBY3_RSTRING_H
 #include "ruby/3/config.h"
 #include "ruby/3/arithmetic/long.h"
 #include "ruby/3/attr/artificial.h"
diff --git a/include/ruby/3/core/rstruct.h b/include/ruby/3/core/rstruct.h
index 55db1b3fc0..d474697e4e 100644
--- a/include/ruby/3/core/rstruct.h
+++ b/include/ruby/3/core/rstruct.h
@@ -1,4 +1,6 @@
-/**                                                     \noop-*-C++-*-vi:ft=cpp
+#ifndef RUBY3_RSTRUCT_H                              /*-*-C++-*-vi:se ft=cpp:*/
+#define RUBY3_RSTRUCT_H
+/**
  * @file
  * @author     Ruby developers <ruby-core@ruby-lang.org>
  * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
@@ -18,8 +20,6 @@
  *             extension libraries. They could be written in C++98.
  * @brief      Routines to manipulate struct ::RStruct.
  */
-#ifndef  RUBY3_RSTRUCT_H
-#define  RUBY3_RSTRUCT_H
 #include "ruby/3/attr/artificial.h"
 #include "ruby/3/dllexport.h"
 #include "ruby/3/value.h"
diff --git a/include/ruby/3/core/rtypeddata.h b/include/ruby/3/core/rtypeddata.h
index cc00fa2500..d46fd5c519 100644
--- a/include/ruby/3/core/rtypeddata.h
+++ b/include/ruby/3/core/rtypeddata.h
@@ -1,4 +1,6 @@
-/**                                                     \noop-*-C++-*-vi:ft=cpp
+#ifndef RUBY3_RTYPEDDATA_H                           /*-*-C++-*-vi:se ft=cpp:*/
+#define RUBY3_RTYPEDDATA_H
+/**
  * @file
  * @author     Ruby developers <ruby-core@ruby-lang.org>
  * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
@@ -18,8 +20,6 @@
  *             extension libraries. They could be written in C++98.
  * @brief      Defines struct ::RTypedData.
  */
-#ifndef  RUBY3_RTYPEDDATA_H
-#define  RUBY3_RTYPEDDATA_H
 #include "ruby/3/config.h"
 
 #ifdef STDC_HEADERS