use do/while(0) around GetDBM macros

* README.EXT: wrap GetDBM with do/while(0)
* README.EXT.ja: ditto
* ext/dbm/dbm.c: ditto, likewise for GetDBM2
* ext/gdbm/gdbm.c: ditto
* ext/sdbm/init.c: ditto
  [ruby-core:61217]

ref: http://c-faq.com/cpp/multistmt.html

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45260 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,12 @@
+Mon Mar  3 07:47:17 2014  Eric Wong  <e@80x24.org>
+
+	* README.EXT: wrap GetDBM with do/while(0)
+	* README.EXT.ja: ditto
+	* ext/dbm/dbm.c: ditto, likewise for GetDBM2
+	* ext/gdbm/gdbm.c: ditto
+	* ext/sdbm/init.c: ditto
+	  [ruby-core:61217]
+
 Mon Mar  3 07:17:31 2014  Zachary Scott  <e@zzak.io>
 
 	* NEWS: [DOC] Update doc regarding filesystem load when flushing IO

README.EXT

@@ -683,10 +683,10 @@ wrapping DBM* directly, because we want to cache size information.
 To retrieve the dbmdata structure from a Ruby object, we define the
 following macro:
 
-  #define GetDBM(obj, dbmp) {\
+  #define GetDBM(obj, dbmp) do {\
       Data_Get_Struct(obj, struct dbmdata, dbmp);\
       if (dbmp->di_dbm == 0) closed_dbm();\
-  }
+  } while (0)
 
 This sort of complicated macro does the retrieving and close checking for
 the DBM.

README.EXT.ja

@@ -763,10 +763,10 @@ dbm.cではData_Make_Structを以下のように使っています．
 Dataオブジェクトからdbmstruct構造体のポインタを取り出すため
 に以下のマクロを使っています．
 
-  #define GetDBM(obj, dbmp) {\
+  #define GetDBM(obj, dbmp) do {\
       Data_Get_Struct(obj, struct dbmdata, dbmp);\
       if (dbmp->di_dbm == 0) closed_dbm();\
-  }
+  } while (0)
 
 ちょっと複雑なマクロですが，要するにdbmdata構造体のポインタ
 の取り出しと，closeされているかどうかのチェックをまとめてい

ext/dbm/dbm.c

@@ -45,16 +45,16 @@ closed_dbm(void)
     rb_raise(rb_eDBMError, "closed DBM file");
 }
 
-#define GetDBM(obj, dbmp) {\
+#define GetDBM(obj, dbmp) do {\
     Data_Get_Struct((obj), struct dbmdata, (dbmp));\
     if ((dbmp) == 0) closed_dbm();\
     if ((dbmp)->di_dbm == 0) closed_dbm();\
-}
+} while (0)
 
-#define GetDBM2(obj, data, dbm) {\
+#define GetDBM2(obj, data, dbm) do {\
     GetDBM((obj), (data));\
     (dbm) = dbmp->di_dbm;\
-}
+} while (0)
 
 static void
 free_dbm(struct dbmdata *dbmp)

ext/gdbm/gdbm.c

@@ -106,10 +106,10 @@ closed_dbm(void)
     if ((dbmp)->di_dbm == 0) closed_dbm();\
 } while (0)
 
-#define GetDBM2(obj, data, dbm) {\
+#define GetDBM2(obj, data, dbm) do {\
     GetDBM((obj), (data));\
     (dbm) = dbmp->di_dbm;\
-}
+} while (0)
 
 static void
 free_dbm(struct dbmdata *dbmp)

ext/sdbm/init.c

@@ -77,16 +77,16 @@ closed_sdbm()
     rb_raise(rb_eDBMError, "closed SDBM file");
 }
 
-#define GetDBM(obj, dbmp) {\
+#define GetDBM(obj, dbmp) do {\
     Data_Get_Struct((obj), struct dbmdata, (dbmp));\
     if ((dbmp) == 0) closed_sdbm();\
     if ((dbmp)->di_dbm == 0) closed_sdbm();\
-}
+} while (0)
 
-#define GetDBM2(obj, data, dbm) {\
+#define GetDBM2(obj, data, dbm) do {\
     GetDBM((obj), (data));\
     (dbm) = dbmp->di_dbm;\
-}
+} while (0)
 
 static void
 free_sdbm(struct dbmdata *dbmp)