Include LDFLAGS in gtkdoc-scangobj command linewip/lantw/include-ldflags-in-gtkdoc-scangobj-command-line

When a library provides no way to find linker flags for linking with it,
the build system usually depends on the user to necessary put -L flags
in LDFLAGS environment variable in order to find it. However, GtkDoc
module constructs the command line by itself, and it forgets to add
LDFLAGS to the command line of gtkdoc-scangobj.

It is especially important to include LDFLAGS on non-GNU systems. For
example, FreeBSD libc doesn't include a gettext implementation. GLib
requires gettext, and it pulls in an external gettext runtime for it.
However, gettext-runtime doesn't include a .pc file, so LDFLAGS is
required if gettext-runtime isn't installed in the same prefix as GLib.
Failing to include LDFLAGS in --ldflags passed to gtkdoc-scangobj can
result in a linking error because -lintl cannot be found.

In evolution-data-server we are lucky most of the time because it
depends on a lot of external libraries. These external libraries are
likely to be installed in the same prefix as gettext-runtime, so not
using LDFLAGS doesn't cause linking failure because required flags are
already pulled in by other libraries. In fact, this problem was found
when building libical, which uses a similar GtkDoc.cmake file.

In addition to the change to include LDFLAGS, this commit also changes
the following things:

 - Instead of constructing _scangobj_ldflags in reverse order, do it in
   normal order. Appending is easier to understand than prepending, and
   the linker also interprets -L and -l flags in normal order.

 - Move -L${LIB_INSTALL_DIR} to the bottom. This is what the comment
   says, and it is expected to work because we no longer constructs
   _scangobj_ldflags in reverse order.

1 files changed, 8 insertions, 3 deletions

diff --git a/cmake/modules/GtkDoc.cmake b/cmake/modules/GtkDoc.cmake
index cc6cc007a..0ba1a7a78 100644
--- a/cmake/modules/GtkDoc.cmake
+++ b/cmake/modules/GtkDoc.cmake
@@ -96,9 +96,8 @@ macro(add_gtkdoc _module _namespace _deprecated_guards _srcdirsvar _depsvar _ign
 		list(APPEND _scangobj_deps ${opt})
 	endforeach(opt)
 
-	# Add them as the last, thus in-tree headers/libs have precedence
+	# Add it as the last, thus in-tree headers have precedence
 	list(APPEND _scangobj_cflags_list -I${INCLUDE_INSTALL_DIR})
-	list(APPEND _scangobj_ldflags -L${LIB_INSTALL_DIR})
 
 	if(_scangobj_deps)
 		list(REMOVE_DUPLICATES _scangobj_deps)
@@ -122,7 +121,7 @@ macro(add_gtkdoc _module _namespace _deprecated_guards _srcdirsvar _depsvar _ign
 				if(NOT _output_name)
 					set(_output_name ${opt})
 				endif(NOT _output_name)
-				set(_scangobj_ldflags "-L$<TARGET_FILE_DIR:${opt}> -l${_output_name} ${_scangobj_ldflags}")
+				set(_scangobj_ldflags "${_scangobj_ldflags} -L$<TARGET_FILE_DIR:${opt}> -l${_output_name}")
 
 				if(_target_type STREQUAL "SHARED_LIBRARY" OR (_target_type STREQUAL "MODULE_LIBRARY"))
 					set(_scangobj_ld_lib_dirs "${_scangobj_ld_lib_dirs}:$<TARGET_FILE_DIR:${opt}>")
@@ -133,12 +132,18 @@ macro(add_gtkdoc _module _namespace _deprecated_guards _srcdirsvar _depsvar _ign
 		endif(TARGET ${opt})
 	endforeach(opt)
 
+	# Add extra flags from LDFLAGS environment variable
+	set(_scangobj_ldflags "${_scangobj_ldflags} ${CMAKE_SHARED_LINKER_FLAGS}")
+
 	foreach(opt IN LISTS _scangobj_deps)
 		if(NOT TARGET ${opt})
 			set(_scangobj_ldflags "${_scangobj_ldflags} ${opt}")
 		endif(NOT TARGET ${opt})
 	endforeach(opt)
 
+	# Add it as the last, thus in-tree libs have precedence
+	set(_scangobj_ldflags "${_scangobj_ldflags} -L${LIB_INSTALL_DIR}")
+
 	set(_scangobj_prefix ${CMAKE_COMMAND} -E env LD_LIBRARY_PATH="${_scangobj_ld_lib_dirs}:${LIB_INSTALL_DIR}:$ENV{LD_LIBRARY_PATH}")
 
 	if(NOT (_scangobj_cflags STREQUAL ""))