Handle usr-move without forcing absolute paths

In qtbase commit 7ac58d1ff0815566ba1de09519299b5119e5ee91 (Make cmake
packages installed to /usr non-relocatable., 2013-02-11), we made
cmake config files non-relocatable if they were installed to
the /usr prefix. That was assumed to mean that this was a distro
or platform package, and was a workaround for the usr-move problem
on Fedora and ArchLinux.

However, cmake bug http://public.kitware.com/Bug/view.php?id=14041
showed that forcing absolute paths in this situation is not desirable
in cross compiling scenarios. CMake commit 6c613b433c45efb0bb013a6bd668cbb8ac740259
(Handle usr-move without forcing absolute paths (#14041), 2013-04-03)
addressed the problem in CMake, and this commit is an equivalent.

Change-Id: I065a6230bc618aa980fae6ca511ae10df4cd62c2
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>

3 files changed, 33 insertions, 9 deletions

diff --git a/mkspecs/features/cmake_functions.prf b/mkspecs/features/cmake_functions.prf
index 62634d9b88..5816dfe1d0 100644
--- a/mkspecs/features/cmake_functions.prf
+++ b/mkspecs/features/cmake_functions.prf
@@ -24,3 +24,10 @@ defineReplace(cmakeModuleList) {
     }
     return ($$join(out, ";"))
 }
+
+defineReplace(cmakeTargetPath) {
+    SYSR = $$[QT_SYSROOT]
+    !isEmpty(SYSR): path = $$relative_path($$1, $$[QT_SYSROOT])
+    else: path = $$1
+    return(/$$path)
+}
diff --git a/mkspecs/features/create_cmake.prf b/mkspecs/features/create_cmake.prf
index cf0acaf4b7..a9757acd17 100644
--- a/mkspecs/features/create_cmake.prf
+++ b/mkspecs/features/create_cmake.prf
@@ -27,19 +27,22 @@ CMAKE_PARTIAL_MODULE_DEPS = $$replace(CMAKE_MODULE_DEPS, ";", ";Qt5::")
 # The /lib paths are made symlinks to the /usr/lib paths. If someone searching
 # for a Qt 5 package finds it in /lib/cmake/Qt5Core, although it has been
 # installed in /usr/lib/cmake/Qt5Core, relative paths to the includes and
-# executables will not work. So, we treat installations to /usr as non-relocatable
-# packages with absolute paths.
-CMAKE_INSTALL_LIBS_DIR = $$[QT_INSTALL_LIBS]
-contains(CMAKE_INSTALL_LIBS_DIR, ^(/usr)?/lib(64)?.*): CMAKE_FORCE_ABSOLUTE_PATHS = True
+# executables will not work.
+# To work around this, we insert code into the generated config files to check
+# at cmake time whether package has been found via a symlink, and correct
+# that to an absolute path. This is only done for installations to
+# the /usr or / prefix.
+CMAKE_INSTALL_LIBS_DIR = $$cmakeTargetPath($$[QT_INSTALL_LIBS])
+contains(CMAKE_INSTALL_LIBS_DIR, ^(/usr)?/lib(64)?.*): CMAKE_USR_MOVE_WORKAROUND = $$CMAKE_INSTALL_LIBS_DIR
 
 CMAKE_INCLUDE_DIR = $$cmakeRelativePath($$[QT_INSTALL_HEADERS], $$[QT_INSTALL_PREFIX])
-!isEmpty(CMAKE_FORCE_ABSOLUTE_PATHS)|contains(CMAKE_INCLUDE_DIR, "^\\.\\./.*") {
+contains(CMAKE_INCLUDE_DIR, "^\\.\\./.*") {
     CMAKE_INCLUDE_DIR = $$[QT_INSTALL_HEADERS]/
     CMAKE_INCLUDE_DIR_IS_ABSOLUTE = True
 }
 
 CMAKE_LIB_DIR = $$cmakeRelativePath($$[QT_INSTALL_LIBS], $$[QT_INSTALL_PREFIX])
-!isEmpty(CMAKE_FORCE_ABSOLUTE_PATHS)|contains(CMAKE_LIB_DIR,"^\\.\\./.*") {
+contains(CMAKE_LIB_DIR,"^\\.\\./.*") {
     CMAKE_LIB_DIR = $$[QT_INSTALL_LIBS]/
     CMAKE_LIB_DIR_IS_ABSOLUTE = True
 } else {
@@ -50,13 +53,13 @@ CMAKE_LIB_DIR = $$cmakeRelativePath($$[QT_INSTALL_LIBS], $$[QT_INSTALL_PREFIX])
 }
 
 CMAKE_BIN_DIR = $$cmakeRelativePath($$[QT_HOST_BINS], $$[QT_INSTALL_PREFIX])
-!isEmpty(CMAKE_FORCE_ABSOLUTE_PATHS)|contains(CMAKE_BIN_DIR, "^\\.\\./.*") {
+contains(CMAKE_BIN_DIR, "^\\.\\./.*") {
     CMAKE_BIN_DIR = $$[QT_HOST_BINS]/
     CMAKE_BIN_DIR_IS_ABSOLUTE = True
 }
 
 CMAKE_HOST_DATA_DIR = $$cmakeRelativePath($$[QT_HOST_DATA], $$[QT_INSTALL_PREFIX])
-!isEmpty(CMAKE_FORCE_ABSOLUTE_PATHS)|contains(CMAKE_HOST_DATA_DIR, "^\\.\\./.*") {
+contains(CMAKE_HOST_DATA_DIR, "^\\.\\./.*") {
     CMAKE_HOST_DATA_DIR = $$[QT_HOST_DATA]/
     CMAKE_HOST_DATA_DIR_IS_ABSOLUTE = True
 }
diff --git a/mkspecs/features/data/cmake/Qt5BasicConfig.cmake.in b/mkspecs/features/data/cmake/Qt5BasicConfig.cmake.in
index d88f6e1224..a77a6bd22d 100644
--- a/mkspecs/features/data/cmake/Qt5BasicConfig.cmake.in
+++ b/mkspecs/features/data/cmake/Qt5BasicConfig.cmake.in
@@ -3,7 +3,21 @@ if (CMAKE_VERSION VERSION_LESS 2.8.3)
     message(FATAL_ERROR \"Qt 5 requires at least CMake version 2.8.3\")
 endif()
 
-!!IF isEmpty(CMAKE_LIB_DIR_IS_ABSOLUTE)
+!!IF !isEmpty(CMAKE_USR_MOVE_WORKAROUND)
+get_filename_component(_IMPORT_PREFIX \"${CMAKE_CURRENT_LIST_FILE}\" PATH)
+# Use original install prefix when loaded through a
+# cross-prefix symbolic link such as /lib -> /usr/lib.
+get_filename_component(_realCurr \"${_IMPORT_PREFIX}\" REALPATH)
+get_filename_component(_realOrig \"$$CMAKE_INSTALL_LIBS_DIR/cmake/Qt5$${CMAKE_MODULE_NAME}\" REALPATH)
+if(_realCurr STREQUAL _realOrig)
+    get_filename_component(_qt5$${CMAKE_MODULE_NAME}_install_prefix \"$$CMAKE_INSTALL_LIBS_DIR\" PATH)
+else()
+    get_filename_component(_qt5$${CMAKE_MODULE_NAME}_install_prefix \"${CMAKE_CURRENT_LIST_DIR}/$${CMAKE_RELATIVE_INSTALL_DIR}\" ABSOLUTE)
+endif()
+unset(_realOrig)
+unset(_realCurr)
+unset(_IMPORT_PREFIX)
+!!ELIF isEmpty(CMAKE_LIB_DIR_IS_ABSOLUTE)
 get_filename_component(_qt5$${CMAKE_MODULE_NAME}_install_prefix \"${CMAKE_CURRENT_LIST_DIR}/$${CMAKE_RELATIVE_INSTALL_DIR}\" ABSOLUTE)
 !!ELSE
 set(_qt5$${CMAKE_MODULE_NAME}_install_prefix \"$$[QT_INSTALL_PREFIX]\")