[PATCH] lib: fix clang build

[Jani Nikula]

On Sun, 18 Aug 2013, Tomi Ollila <tomi.ollila at iki.fi> wrote:
> On Sun, Aug 18 2013, Jani Nikula <jani at nikula.org> wrote:
>
>> Long story short, fix build on recent (3.2+) clang.
>>
>> The long story for posterity follows.
>>
>> gcc 4.6 added new warnings about structs with greater visibility than
>> their fields. The warnings were silenced by adjusting visibility in
>>
>> commit d5523ead90b6be2b07d4af745b8ed9b980a6b9f1
>> Author: Carl Worth <cworth at cworth.org>
>> Date:   Wed May 11 13:23:13 2011 -0700
>>
>>     Mark some structures in the library interface with visibility=default attribute.
>>
>> Later on,
>>
>> commit 3b76adf9e2c026dd03b820f4c6eab50e25444113
>> Author: Austin Clements <amdragon at MIT.EDU>
>> Date:   Sat Jan 14 19:17:33 2012 -0500
>>
>>     lib: Add support for automatically excluding tags from queries
>>
>> changed visibility of struct _notmuch_string_list for the same reason, and
>>
>> commit 1a53f9f116fa7c460cda3df532be921baaafb082
>> Author: Mark Walters <markwalters1009 at gmail.com>
>> Date:   Thu Mar 1 22:30:38 2012 +0000
>>
>>     lib: Add the exclude flag to notmuch_query_search_threads
>>
>> split the struct _notmuch_string_list and its typedef
>> notmuch_string_list_t as a way to make a forward declaration for
>> _notmuch_thread_create().
>>
>> The subtle difference was that the struct definition now had 'visible'
>> in it, while the typedef didn't, and it was within the #pragma GCC
>> visibility push(hidden) block. This went unnoticed, as the then common
>> versions of clang didn't care about this.
>>
>> A later change in clang (I did not dig into when this change was
>> introduced) caused the following error:
>>
>> CXX  -O2 lib/database.o
>> In file included from lib/database.cc:21:
>> In file included from ./lib/database-private.h:33:
>> ./lib/notmuch-private.h:479:8: error: visibility does not match previous declaration
>> struct visible _notmuch_string_list {
>>        ^
>> ./lib/notmuch-private.h:67:33: note: expanded from macro 'visible'
>>                                 ^
>> ./lib/notmuch-private.h:52:13: note: previous attribute is here
>>             ^
>> 1 error generated.
>> make: *** [lib/database.o] Error 1
>>
>> This is slightly misleading due to the reference to the #pragma. The
>> real culprit is the typedef within the #pragma.
>>
>> We could just add 'visible' to the typedef, or move the typedef
>> outside of the #pragma, and be done with it, but juggle the
>> declarations a bit to accommodate moving the typedef back with the
>> struct, and keep the visibility attribute in one place.
>>
>> The problem was originally reported by Simonas Kazlauskas
>> <s at kazlauskas.me> in id:20130418102507.GA23688 at godbox but I was only
>> able to reproduce and investigate now that I upgraded clang.
>> ---
>>  lib/notmuch-private.h |   28 +++++++++++++---------------
>>  1 file changed, 13 insertions(+), 15 deletions(-)
>>
>> diff --git a/lib/notmuch-private.h b/lib/notmuch-private.h
>> index eced03e..af185c7 100644
>> --- a/lib/notmuch-private.h
>> +++ b/lib/notmuch-private.h
>> @@ -162,8 +162,6 @@ typedef enum _notmuch_find_flags {
>>  
>>  typedef struct _notmuch_doc_id_set notmuch_doc_id_set_t;
>
> Looks good to me (except log message is a bit excessive (?) maybe
> it is reasonable to have it, though (TL;DR ;)...
>>  
>> -typedef struct _notmuch_string_list notmuch_string_list_t;
>> -
>
> anyway, would
>
> typedef struct visible _notmuch_string_list notmuch_string_list_t;
>
> have helped here (if yes is your resolution nicer ?? :D )

Yes, it would have. Read the commit message! :p

Jani.


>
> Tomi
>
>
>>  /* database.cc */
>>  
>>  /* Lookup a prefix value by name.
>> @@ -228,17 +226,6 @@ _notmuch_directory_create (notmuch_database_t *notmuch,
>>  unsigned int
>>  _notmuch_directory_get_document_id (notmuch_directory_t *directory);
>>  
>> -/* thread.cc */
>> -
>> -notmuch_thread_t *
>> -_notmuch_thread_create (void *ctx,
>> -			notmuch_database_t *notmuch,
>> -			unsigned int seed_doc_id,
>> -			notmuch_doc_id_set_t *match_set,
>> -			notmuch_string_list_t *excluded_terms,
>> -			notmuch_exclude_t omit_exclude,
>> -			notmuch_sort_t sort);
>> -
>>  /* message.cc */
>>  
>>  notmuch_message_t *
>> @@ -476,11 +463,11 @@ typedef struct _notmuch_string_node {
>>      struct _notmuch_string_node *next;
>>  } notmuch_string_node_t;
>>  
>> -struct visible _notmuch_string_list {
>> +typedef struct visible _notmuch_string_list {
>>      int length;
>>      notmuch_string_node_t *head;
>>      notmuch_string_node_t **tail;
>> -};
>> +} notmuch_string_list_t;
>>  
>>  notmuch_string_list_t *
>>  _notmuch_string_list_create (const void *ctx);
>> @@ -509,6 +496,17 @@ notmuch_filenames_t *
>>  _notmuch_filenames_create (const void *ctx,
>>  			   notmuch_string_list_t *list);
>>  
>> +/* thread.cc */
>> +
>> +notmuch_thread_t *
>> +_notmuch_thread_create (void *ctx,
>> +			notmuch_database_t *notmuch,
>> +			unsigned int seed_doc_id,
>> +			notmuch_doc_id_set_t *match_set,
>> +			notmuch_string_list_t *excluded_terms,
>> +			notmuch_exclude_t omit_exclude,
>> +			notmuch_sort_t sort);
>> +
>>  NOTMUCH_END_DECLS
>>  
>>  #ifdef __cplusplus
>> -- 
>> 1.7.10.4
>>
>> _______________________________________________
>> notmuch mailing list
>> notmuch at notmuchmail.org
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