ENH: Improved default choice of -64 compiler/linker flags based on how cmake was built.

Modules/Platform/IRIX64.cmake

@@ -4,15 +4,40 @@ SET(CMAKE_SHARED_LIBRARY_CREATE_CXX_FLAGS "-shared -rdata_shared")
 SET(CMAKE_SHARED_LIBRARY_RUNTIME_FLAG "-Wl,-rpath,")       # -rpath
 SET(CMAKE_SHARED_LIBRARY_RUNTIME_FLAG_SEP "")   # : or empty
 IF(NOT CMAKE_COMPILER_IS_GNUCXX)
+  # Set default flags init.
+  SET(CMAKE_C_FLAGS_INIT "")
+  SET(CMAKE_CXX_FLAGS_INIT "")
+  SET(CMAKE_EXE_LINKER_FLAGS_INIT "")
+  SET(CMAKE_SHARED_LINKER_FLAGS_INIT "")
+  SET(CMAKE_MODULE_LINKER_FLAGS_INIT "")
+  
+  # If no -o32, -n32, or -64 flag is given, set a reasonable default.
+  IF("$ENV{CFLAGS} $ENV{CXXFLAGS} $ENV{LDFLAGS}" MATCHES "-([no]32|64)")
+  ELSE("$ENV{CFLAGS} $ENV{CXXFLAGS} $ENV{LDFLAGS}" MATCHES "-([no]32|64)")
+    # Check if this is a 64-bit CMake.
+    IF(CMAKE_FILE_SELF MATCHES "^CMAKE_FILE_SELF$")
+      EXEC_PROGRAM(file ARGS ${CMAKE_COMMAND} OUTPUT_VARIABLE CMAKE_FILE_SELF)
+      SET(CMAKE_FILE_SELF "${CMAKE_FILE_SELF}" CACHE INTERNAL
+        "Output of file command on ${CMAKE_COMMAND}.")
+    ENDIF(CMAKE_FILE_SELF MATCHES "^CMAKE_FILE_SELF$")
+    
+    # Set initial flags to match cmake executable.
+    IF(CMAKE_FILE_SELF MATCHES " 64-bit ")
+      SET(CMAKE_C_FLAGS_INIT "-64")
+      SET(CMAKE_CXX_FLAGS_INIT "-64")
+      SET(CMAKE_EXE_LINKER_FLAGS_INIT "-64")
+      SET(CMAKE_SHARED_LINKER_FLAGS_INIT "-64")
+      SET(CMAKE_MODULE_LINKER_FLAGS_INIT "-64")
+    ENDIF(CMAKE_FILE_SELF MATCHES " 64-bit ")
+  ENDIF("$ENV{CFLAGS} $ENV{CXXFLAGS} $ENV{LDFLAGS}" MATCHES "-([no]32|64)")
+  
+  # Set remaining defaults.
   SET(CMAKE_CXX_CREATE_STATIC_LIBRARY
       "<CMAKE_CXX_COMPILER> -ar -o <TARGET> <OBJECTS>")
-  SET (CMAKE_CXX_FLAGS_INIT "")
   SET (CMAKE_CXX_FLAGS_DEBUG_INIT "-g")
   SET (CMAKE_CXX_FLAGS_MINSIZEREL_INIT "-O3")
   SET (CMAKE_CXX_FLAGS_RELEASE_INIT "-O2")
   SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "-O2")
-  SET (CMAKE_C_FLAGS_INIT "")
 ELSE(NOT CMAKE_COMPILER_IS_GNUCXX)
   INCLUDE(${CMAKE_ROOT}/Modules/Platform/gcc.cmake)
 ENDIF(NOT CMAKE_COMPILER_IS_GNUCXX)
-