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@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@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@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@kazlauskas.me> in id:
20130418102507.GA23688@godbox but I was only
able to reproduce and investigate now that I upgraded clang.