[PATCH] ruby: extern linkage portability improvement

[Tomi Ollila]

Some C compilers are stricter when it comes to (tentative) definition
of a variable -- in those compilers introducing variable without 'extern'
keyword always allocates new 'storage' to the variable and linking all
these modules fails due to duplicate symbols.

This change uses some macro trickery to avoid writing every variable twice.

This is reimplementation of Charlie Allom's patch:
id:"1336481467-66356-1-git-send-email-charlie at mediasp.com"

combining information from other change made by Ali Polatel.
---

Charlie: could you test whether this patch actually work ? :)

Everyone: what do you think of the "hiding extern" macro trick ?

 bindings/ruby/defs.h |   56 +++++++++++++++++++++++++++----------------------
 bindings/ruby/init.c |    2 +
 2 files changed, 33 insertions(+), 25 deletions(-)

diff --git a/bindings/ruby/defs.h b/bindings/ruby/defs.h
index 85d8205..2531760 100644
--- a/bindings/ruby/defs.h
+++ b/bindings/ruby/defs.h
@@ -24,31 +24,37 @@
 #include <ruby.h>
 #include "notmuch.h"
 
-VALUE notmuch_rb_cDatabase;
-VALUE notmuch_rb_cDirectory;
-VALUE notmuch_rb_cFileNames;
-VALUE notmuch_rb_cQuery;
-VALUE notmuch_rb_cThreads;
-VALUE notmuch_rb_cThread;
-VALUE notmuch_rb_cMessages;
-VALUE notmuch_rb_cMessage;
-VALUE notmuch_rb_cTags;
-
-VALUE notmuch_rb_eBaseError;
-VALUE notmuch_rb_eDatabaseError;
-VALUE notmuch_rb_eMemoryError;
-VALUE notmuch_rb_eReadOnlyError;
-VALUE notmuch_rb_eXapianError;
-VALUE notmuch_rb_eFileError;
-VALUE notmuch_rb_eFileNotEmailError;
-VALUE notmuch_rb_eNullPointerError;
-VALUE notmuch_rb_eTagTooLongError;
-VALUE notmuch_rb_eUnbalancedFreezeThawError;
-VALUE notmuch_rb_eUnbalancedAtomicError;
-
-ID ID_call;
-ID ID_db_create;
-ID ID_db_mode;
+#ifdef RUBY_INIT_C
+#define extern
+#endif
+
+extern VALUE notmuch_rb_cDatabase;
+extern VALUE notmuch_rb_cDirectory;
+extern VALUE notmuch_rb_cFileNames;
+extern VALUE notmuch_rb_cQuery;
+extern VALUE notmuch_rb_cThreads;
+extern VALUE notmuch_rb_cThread;
+extern VALUE notmuch_rb_cMessages;
+extern VALUE notmuch_rb_cMessage;
+extern VALUE notmuch_rb_cTags;
+
+extern VALUE notmuch_rb_eBaseError;
+extern VALUE notmuch_rb_eDatabaseError;
+extern VALUE notmuch_rb_eMemoryError;
+extern VALUE notmuch_rb_eReadOnlyError;
+extern VALUE notmuch_rb_eXapianError;
+extern VALUE notmuch_rb_eFileError;
+extern VALUE notmuch_rb_eFileNotEmailError;
+extern VALUE notmuch_rb_eNullPointerError;
+extern VALUE notmuch_rb_eTagTooLongError;
+extern VALUE notmuch_rb_eUnbalancedFreezeThawError;
+extern VALUE notmuch_rb_eUnbalancedAtomicError;
+
+extern ID ID_call;
+extern ID ID_db_create;
+extern ID ID_db_mode;
+
+#undef extern
 
 /* RSTRING_PTR() is new in ruby-1.9 */
 #if !defined(RSTRING_PTR)
diff --git a/bindings/ruby/init.c b/bindings/ruby/init.c
index 3fe60fb..b2dc7f6 100644
--- a/bindings/ruby/init.c
+++ b/bindings/ruby/init.c
@@ -18,7 +18,9 @@
  * Author: Ali Polatel <alip at exherbo.org>
  */
 
+#define RUBY_INIT_C
 #include "defs.h"
+#undef RUBY_INIT_C
 
 /*
  * Document-module: Notmuch
-- 
1.7.8.2