Add GFLAGS_INCLUDE_DIR CMake variable (Fixes issue #80).

Both GFLAGS_NAMESPACE and GFLAGS_INCLUDE_DIR can be used to customize the installation of the gflags library. One specifies the C++ namespace name of the gflags symbols, the other the include subdirectory path of the public header files. By default, both are set to "gflags", but other Google libraries still expect "google" as C++ namespace name, but not necessarily also include path.

CMakeLists.txt

@@ -25,6 +25,14 @@ version_numbers (
 # ----------------------------------------------------------------------------
 # options
 set (GFLAGS_NAMESPACE   "${PACKAGE_NAME}" CACHE STRING "C++ namespace identifier of gflags library.")
+set (GFLAGS_INCLUDE_DIR "${PACKAGE_NAME}" CACHE STRING "Include subdirectory of gflags header files.")
+
+if (IS_ABSOLUTE GFLAGS_INCLUDE_DIR)
+  message (FATAL_ERROR "GFLAGS_INCLUDE_DIR must be a path relative to CMAKE_INSTALL_PREFIX/include")
+endif ()
+if (GFLAGS_INCLUDE_DIR MATCHES "^\\.\\.[/\\]")
+  message (FATAL_ERROR "GFLAGS_INCLUDE_DIR must not start with parent directory reference (../)")
+endif ()
 
 option (BUILD_SHARED_LIBS          "Request build of shared libraries."                                       OFF)
 option (BUILD_STATIC_LIBS          "Request build of static libraries (default if BUILD_SHARED_LIBS is OFF)." OFF)
@@ -38,6 +46,7 @@ option (INSTALL_HEADERS            "Request packaging of headers and other devel
 mark_as_advanced (CLEAR CMAKE_INSTALL_PREFIX)
 mark_as_advanced (CMAKE_CONFIGURATION_TYPES
                   GFLAGS_NAMESPACE
+                  GFLAGS_INCLUDE_DIR
                   BUILD_STATIC_LIBS
                   BUILD_NC_TESTS
                   INSTALL_HEADERS)
@@ -212,7 +221,7 @@ configure_sources (GFLAGS_SRCS  ${GFLAGS_SRCS})
 
 include_directories ("${PROJECT_SOURCE_DIR}/src")
 include_directories ("${PROJECT_BINARY_DIR}/include")
-include_directories ("${PROJECT_BINARY_DIR}/include/${GFLAGS_NAMESPACE}")
+include_directories ("${PROJECT_BINARY_DIR}/include/${GFLAGS_INCLUDE_DIR}")
 
 # ----------------------------------------------------------------------------
 # output directories
@@ -282,7 +291,7 @@ configure_file (cmake/version.cmake.in "${PROJECT_BINARY_DIR}/${PACKAGE_NAME}-co
 
 install (TARGETS ${TARGETS} DESTINATION ${LIBRARY_INSTALL_DIR} EXPORT gflags-lib)
 if (INSTALL_HEADERS)
-  install (FILES ${PUBLIC_HDRS} DESTINATION ${INCLUDE_INSTALL_DIR}/${GFLAGS_NAMESPACE})
+  install (FILES ${PUBLIC_HDRS} DESTINATION ${INCLUDE_INSTALL_DIR}/${GFLAGS_INCLUDE_DIR})
   install (
     FILES "${PROJECT_BINARY_DIR}/${PACKAGE_NAME}-config-install.cmake"
     RENAME ${PACKAGE_NAME}-config.cmake

cmake/utils.cmake

@@ -47,11 +47,11 @@ function (configure_headers out)
   set (tmp)
   foreach (src IN LISTS ARGN)
     if (EXISTS "${PROJECT_SOURCE_DIR}/src/${src}.in")
-      configure_file ("${PROJECT_SOURCE_DIR}/src/${src}.in" "${PROJECT_BINARY_DIR}/include/${GFLAGS_NAMESPACE}/${src}" @ONLY)
-      list (APPEND tmp "${PROJECT_BINARY_DIR}/include/${GFLAGS_NAMESPACE}/${src}")
+      configure_file ("${PROJECT_SOURCE_DIR}/src/${src}.in" "${PROJECT_BINARY_DIR}/include/${GFLAGS_INCLUDE_DIR}/${src}" @ONLY)
+      list (APPEND tmp "${PROJECT_BINARY_DIR}/include/${GFLAGS_INCLUDE_DIR}/${src}")
     else ()
-	    configure_file ("${PROJECT_SOURCE_DIR}/src/${src}" "${PROJECT_BINARY_DIR}/include/${GFLAGS_NAMESPACE}/${src}" COPYONLY)
-      list (APPEND tmp "${PROJECT_BINARY_DIR}/include/${GFLAGS_NAMESPACE}/${src}")
+	    configure_file ("${PROJECT_SOURCE_DIR}/src/${src}" "${PROJECT_BINARY_DIR}/include/${GFLAGS_INCLUDE_DIR}/${src}" COPYONLY)
+      list (APPEND tmp "${PROJECT_BINARY_DIR}/include/${GFLAGS_INCLUDE_DIR}/${src}")
     endif ()
   endforeach ()
   set (${out} "${tmp}" PARENT_SCOPE)
@@ -63,8 +63,8 @@ function (configure_sources out)
   set (tmp)
   foreach (src IN LISTS ARGN)
     if (src MATCHES ".h$" AND EXISTS "${PROJECT_SOURCE_DIR}/src/${src}.in")
-      configure_file ("${PROJECT_SOURCE_DIR}/src/${src}.in" "${PROJECT_BINARY_DIR}/include/${GFLAGS_NAMESPACE}/${src}" @ONLY)
-      list (APPEND tmp "${PROJECT_BINARY_DIR}/include/${GFLAGS_NAMESPACE}/${src}")
+      configure_file ("${PROJECT_SOURCE_DIR}/src/${src}.in" "${PROJECT_BINARY_DIR}/include/${GFLAGS_INCLUDE_DIR}/${src}" @ONLY)
+      list (APPEND tmp "${PROJECT_BINARY_DIR}/include/${GFLAGS_INCLUDE_DIR}/${src}")
     else ()
       list (APPEND tmp "${PROJECT_SOURCE_DIR}/src/${src}")
     endif ()