Make sure ${WRKSRC}/lib is passed before /usr/local/lib when linking.

This is another shot at fixing the linkage problems that have plagued our
users particularly when upgrading from Qt 5.x to 5.(x+1). Quick recap: in
Qt5, qmake will by default pass QMAKE_LIBDIR to the linker before other
directories such as ${WRKSRC}/lib, which is where the port's libraries are
built. When a user is upgrading Qt, we can end up with the following linker
line:
  c++ -o SomeBinary -lfoo1 -L/usr/local/lib -L${WRKSRC}/lib -lfoo2 -lfoo3
If libfoo2.so is being built by the port and an older version is currently
installed on the system, /usr/local/lib/libfoo2.so will be picked up instead
of the newly-built ${WRKSRC}/lib/libfoo2.so. At best things just work, at
worst SomeBinary needs some new symbol that is not present in the old
libfoo2.so and linking fails. Case in point: bug 198720.

The previous approach, adopted when fixing bug 194088, was to stop setting
QMAKE_{INC,LIB}DIR in the FreeBSD mkspecs and set the CPATH and LIBRARY_PATH
environment variables in Uses/qmake.mk. This way we just did not pass
-L/usr/local/lib to the linker at all and things mostly worked. However,
people using Qt to build their own software without the ports tree were out
of luck, as they would then need need to deal with passing
/usr/local/{include,lib} to the compiler/linker themselves (bug 195105). Not
only that, but if a dependency mentioned /usr/local/lib we would still have
problems anyway (in bug 198720, the GStreamer pkg-config files contain
-L/usr/local/lib, for example).

We now solve the issue by setting the QMAKE_LIBDIR_FLAGS variable in
.qmake.cache to ${WRKSRC}/lib instead. qmake appends the value of
QMAKE_LIBDIR to QMAKE_LIBDIR_FLAGS, so we are always sure -L${WRKSRC}/lib
will come before -L/usr/local/lib in the linker options. Moreover, qmake is
smart enough to automatically call sed(1) and remove references to
${WRKSRC}/lib from .prl and .pc files when installing them.

PR:		194088
PR:		195105
PR:		198720
MFH:		2015Q4

1 files changed, 11 insertions, 2 deletions

diff --git a/Mk/bsd.qt.mk b/Mk/bsd.qt.mk
index 5f1fb4968955..e3e8198788eb 100644
--- a/Mk/bsd.qt.mk
+++ b/Mk/bsd.qt.mk
@@ -604,15 +604,24 @@ post-configure: qmake-configure
 .  endif
 . endif # ${QT_DIST} == "base"
 
+pre-configure: qt5-pre-configure
+qt5-pre-configure:
 # Qt 5.3.2 introduced a check in mkspecs/features/create_cmake.prf that
 # requires tests/auto/cmake to be present, otherwise the configure stage will
 # fail.
 # Since we cannot extract tests/auto/cmake/ and exclude tests/ at the same
 # time, we have to disable the check in a cache file (the only way to get this
 # value through to the configure script in qtbase).
-pre-configure: qt5-pre-configure
-qt5-pre-configure:
 	${ECHO_CMD} 'CMAKE_MODULE_TESTS = -' > ${WRKSRC}/.qmake.cache
+# We piggyback on QMAKE_LIBDIR_FLAGS to make sure -L${WRKSRC}/lib is passed to
+# the linker before -L/usr/local/lib. By default, the opposite happens, which
+# is a problem when a Qt port is being upgraded, since an existing library
+# would end up being picked up instead of those built in ${WRKSRC}/lib. Since
+# qmake appends the value of QMAKE_LIBDIR to QMAKE_LIBDIR_FLAGS, we can use the
+# latter to get the linker path order right. qmake is smart enough to strip
+# occurrences of ${WRKSRC}/lib from .pc and .prl files when installing them.
+# See QTBUG-40825 and ports bugs 194088, 195105 and 198720.
+	${ECHO_CMD} 'QMAKE_LIBDIR_FLAGS = -L${WRKSRC}/lib' >> ${WRKSRC}/.qmake.cache
 
 pre-install: qt-pre-install
 qt-pre-install: