[PATCH] ruby: extern linkage portability improvement

[Ali Polatel]

2012/5/13 Austin Clements <amdragon at 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 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 ?
>
> 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

>>  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
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