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From: David Bremner <david@tethera.net>
To: Charles Celerier <cceleri@cs.stanford.edu>, Notmuch Mail
	<notmuch@notmuchmail.org>
Subject: Re: [PATCH v2 5/5] T360-symbol-hiding: Use nm instead of objdump.
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Charles Celerier <cceleri@cs.stanford.edu> writes:

> David Bremner <david@tethera.net> writes:
>
>     $ objdump -t lib/*.o | sed -n '/\[\.text\] __\?notmuch/p' | tail
>     00000000000009a0 g       0f SECT   01 0000 [.text] _notmuch_thread_get_authors
>     0000000000000990 g       0f SECT   01 0000 [.text] _notmuch_thread_get_matched_messages
>     0000000000000960 g       0f SECT   01 0000 [.text] _notmuch_thread_get_messages
>     00000000000009d0 g       0f SECT   01 0000 [.text] _notmuch_thread_get_newest_date

Here is some equivalent output from Linux

$ objdump -t lib/*.o | sed -n '/[.]text.*notmuch/p' | tail -12

0000000000000150 g     F .text	000000000000095e .hidden _notmuch_thread_create
0000000000000ab0 g     F .text	0000000000000009 notmuch_thread_get_toplevel_messages
0000000000000ac0 g     F .text	0000000000000009 notmuch_thread_get_messages

...

Notice in particular the ".hidden" in the first line. Also, the lack of
extra _ on the front.  

It may be that the visibility information is not accessible on OS-X
using objdump; this is something different than whether a symbol is
extern. The symbols marked .hidden can be used across compilation unit
boundaries, but will not be exported from the shared library.