From: Tomi Ollila <tomi.ollila@iki.fi>
To: Ali Polatel <alip@exherbo.org>, Austin Clements <amdragon@mit.edu>
Subject: Re: [PATCH] ruby: extern linkage portability improvement
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	<20120513171917.GL11804@mit.edu>
	<CADv3eywyAaqtAhzYJFjVp9xpWcPv35L1CGPYK3PK_GaDrAJOVw@mail.gmail.com>
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Date: Tue, 15 May 2012 18:31:45 +0300
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On Tue, May 15 2012, Ali Polatel <alip@exherbo.org> wrote:

> 2012/5/13 Austin Clements <amdragon@mit.edu>:
>> Quoth Tomi Ollila on May 10 at .8:12 pm:
>>> 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@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 ?
>>
>> This seems like a hacky and nonstandard way to do this. .Granted, the
>> standard way to do this---always declare variables extern in .h files
>> and also give a non-extern definition in exactly one .c file---is more
>> verbose, but nobody will be surprised or confused by it.
>
> I fully agree or otherwise I'd suggest using:
> http://minnie.tuhs.org/cgi-bin/utree.pl?file=V7/usr/src/cmd/sh/mac.h

Yes...

(Hmm, I hope no-one got confused that the trick was mine and not yours :)

So, the patch you provided in github would be good...

Tomi

>
>>> .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@exherbo.org>
>>> . */
>>>
>>> +#define RUBY_INIT_C
>>> .#include "defs.h"
>>> +#undef RUBY_INIT_C
>>>
>>> ./*
>>> . * Document-module: Notmuch