cmake: Fix paths with absolute GNUInstallDirs

It is not generally true that `CMAKE_INSTALL_<dir>` variables are relative paths:

https://github.com/jtojnar/cmake-snips#concatenating-paths-when-building-pkg-config-files
https://github.com/jtojnar/cmake-snips#assuming-cmake_install_dir-is-relative-path

Let's join them properly as paths, not strings.

On Windows, the absolute paths will likely remain unsupported as neither the CMake function,
nor the C++ code is able to detect absolute paths.

Signed-off-by: Jan Tojnar <jtojnar@gmail.com>

CMakeLists.txt

@@ -135,6 +135,8 @@ if (EXIV2_TEAM_PACKAGING)
     include(cmake/packaging.cmake)
 endif()
 
+join_paths(libdir_for_pc_file "\${prefix}" "${CMAKE_INSTALL_LIBDIR}")
+join_paths(includedir_for_pc_file "\${prefix}" "${CMAKE_INSTALL_INCLUDEDIR}")
 configure_file(cmake/exiv2.pc.in exiv2.pc @ONLY)
 install(FILES ${CMAKE_CURRENT_BINARY_DIR}/exiv2.pc DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig)
 

cmake/JoinPaths.cmake

@@ -0,0 +1,24 @@
+# This module provides function for joining paths
+# known from from most languages
+#
+# Original license:
+# SPDX-License-Identifier: (MIT OR CC0-1.0)
+# Copyright 2020 Jan Tojnar
+# https://github.com/jtojnar/cmake-snips
+#
+# Modelled after Python’s os.path.join
+# https://docs.python.org/3.7/library/os.path.html#os.path.join
+# Windows not supported
+function(join_paths joined_path first_path_segment)
+    set(temp_path "${first_path_segment}")
+    foreach(current_segment IN LISTS ARGN)
+        if(NOT ("${current_segment}" STREQUAL ""))
+            if(IS_ABSOLUTE "${current_segment}")
+                set(temp_path "${current_segment}")
+            else()
+                set(temp_path "${temp_path}/${current_segment}")
+            endif()
+        endif()
+    endforeach()
+    set(${joined_path} "${temp_path}" PARENT_SCOPE)
+endfunction()

cmake/exiv2.pc.in

@@ -1,7 +1,7 @@
 prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=${prefix}
-libdir=${prefix}/@CMAKE_INSTALL_LIBDIR@
-includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@
+libdir=@libdir_for_pc_file@
+includedir=@includedir_for_pc_file@
 
 Name: exiv2
 Description: @PROJECT_DESCRIPTION@

cmake/mainSetup.cmake

@@ -5,6 +5,7 @@ include(GNUInstallDirs)
 include(CheckFunctionExists)
 include(GenerateExportHeader)
 include(CMakeDependentOption)
+include(cmake/JoinPaths.cmake)
 
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
@@ -23,7 +24,7 @@ if (UNIX)
         set(CMAKE_MACOSX_RPATH ON)
         set(CMAKE_INSTALL_RPATH "@loader_path")
     else()
-        set(CMAKE_INSTALL_RPATH "$ORIGIN/../${CMAKE_INSTALL_LIBDIR}")
+        join_paths(CMAKE_INSTALL_RPATH "$ORIGIN" ".." "${CMAKE_INSTALL_LIBDIR}")
     endif()
 endif()
 

src/CMakeLists.txt

@@ -215,7 +215,8 @@ if( EXIV2_ENABLE_NLS )
     target_include_directories(exiv2lib PRIVATE ${Intl_INCLUDE_DIRS})
     target_include_directories(exiv2lib_int PRIVATE ${Intl_INCLUDE_DIRS})
     # Definition needed for translations
-    target_compile_definitions(exiv2lib PUBLIC EXV_LOCALEDIR="/../${CMAKE_INSTALL_LOCALEDIR}")
+    join_paths(EXV_LOCALEDIR ".." "${CMAKE_INSTALL_LOCALEDIR}")
+    target_compile_definitions(exiv2lib PUBLIC EXV_LOCALEDIR="${EXV_LOCALEDIR}")
 endif()
 
 if( ICONV_FOUND )

src/exiv2.cpp

@@ -132,7 +132,7 @@ int main(int argc, char* const argv[])
 
 #ifdef EXV_ENABLE_NLS
     setlocale(LC_ALL, "");
-    const std::string localeDir = Exiv2::getProcessPath() + EXV_LOCALEDIR;
+    const std::string localeDir = EXV_LOCALEDIR[0] == '/' ? EXV_LOCALEDIR : (Exiv2::getProcessPath() + EXV_SEPARATOR_STR + EXV_LOCALEDIR);
     bindtextdomain(EXV_PACKAGE_NAME, localeDir.c_str());
     textdomain(EXV_PACKAGE_NAME);
 #endif

src/types.cpp

@@ -729,7 +729,7 @@ const char* _exvGettext(const char* str)
 
     if (!exvGettextInitialized) {
         //bindtextdomain(EXV_PACKAGE_NAME, EXV_LOCALEDIR);
-        const std::string localeDir = Exiv2::getProcessPath() + EXV_LOCALEDIR;
+        const std::string localeDir = EXV_LOCALEDIR[0] == '/' ? EXV_LOCALEDIR : (Exiv2::getProcessPath() + EXV_SEPARATOR_STR + EXV_LOCALEDIR);
         bindtextdomain(EXV_PACKAGE_NAME, localeDir.c_str());
 # ifdef EXV_HAVE_BIND_TEXTDOMAIN_CODESET
         bind_textdomain_codeset (EXV_PACKAGE_NAME, "UTF-8");