[PATCH v2] lib: make notmuch shared library install_name be full path on Mac OS X

[J. Lewis Muir]

The install_name of libnotmuch.dylib on Mac OS X is what is written
into a program that links against it.  If it is just the name of the
shared library file, as opposed to the full path, the program won't be
able to find it when it runs and will abort.  Instead, the install_name
should be the full path to the shared library (in its final installed
location).

Why does Notmuch work without this patch when installed via Homebrew?
The answer is twofold.  One, /usr/local/lib is a special location in
which the dynamic linker will look by default to find shared libraries.
Homebrew highly recommends installing to /usr/local, and, assuming it
has been configured this way, the Notmuch library will end up installed
in /usr/local/lib, and the dynamic linker will find it.  Two, Homebrew
globally corrects all install names in dynamically shared libraries and
binaries for each package it installs.  So, even if the install names in
a package's binaries and libraries are incorrect, Homebrew corrects them
automatically, and no one ever knows.

Why does Notmuch work without this patch when installed via MacPorts?
The answer is that MacPorts applies a patch just like this patch to fix
the same problem.
---
 lib/Makefile.local | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/Makefile.local b/lib/Makefile.local
index 7278f46..f9ecd50 100644
--- a/lib/Makefile.local
+++ b/lib/Makefile.local
@@ -27,7 +27,7 @@ LIBRARY_SUFFIX = dylib
 LINKER_NAME = libnotmuch.$(LIBRARY_SUFFIX)
 SONAME = libnotmuch.$(LIBNOTMUCH_VERSION_MAJOR).$(LIBRARY_SUFFIX)
 LIBNAME = libnotmuch.$(LIBNOTMUCH_VERSION_MAJOR).$(LIBNOTMUCH_VERSION_MINOR).$(LIBNOTMUCH_VERSION_RELEASE).$(LIBRARY_SUFFIX)
-LIBRARY_LINK_FLAG = -dynamiclib -install_name $(SONAME) -compatibility_version $(LIBNOTMUCH_VERSION_MAJOR).$(LIBNOTMUCH_VERSION_MINOR) -current_version $(LIBNOTMUCH_VERSION_MAJOR).$(LIBNOTMUCH_VERSION_MINOR).$(LIBNOTMUCH_VERSION_RELEASE)
+LIBRARY_LINK_FLAG = -dynamiclib -install_name $(libdir)/$(SONAME) -compatibility_version $(LIBNOTMUCH_VERSION_MAJOR).$(LIBNOTMUCH_VERSION_MINOR) -current_version $(LIBNOTMUCH_VERSION_MAJOR).$(LIBNOTMUCH_VERSION_MINOR).$(LIBNOTMUCH_VERSION_RELEASE)
 else
 LIBRARY_SUFFIX = so
 LINKER_NAME = libnotmuch.$(LIBRARY_SUFFIX)
-- 
1.9.3 (Apple Git-50)

This version of the patch has a better commit message as suggested
by David Bremner on the mailing list.  The steps for reproducing the
problem and the steps showing the analysis of the problem have been
removed.  Added is an answer to the question of why Notmuch works
without this patch when installed via Homebrew and MacPorts.

The message-id of the previous version of this patch is
1409541227-38895-1-git-send-email-jlmuir at imca-cat.org.