ENH: Added global property FIND_LIBRARY_USE_LIB64_PATHS to allow lib64 paths to be searched optionally. Turn off the feature on debian systems. This addresses debian report 419007.

Modules/Platform/Linux.cmake

@@ -48,3 +48,9 @@ ELSE(DEFINED CMAKE_INSTALL_SO_NO_EXE)
 ENDIF(DEFINED CMAKE_INSTALL_SO_NO_EXE)
 
 INCLUDE(Platform/UnixPaths)
+
+# Debian has lib64 paths only for compatibility so they should not be
+# searched.
+IF(EXISTS "/etc/debian_version")
+  SET_PROPERTIES(GLOBAL PROPERTIES FIND_LIBRARY_USE_LIB64_PATHS FALSE)
+ENDIF(EXISTS "/etc/debian_version")

Modules/Platform/UnixPaths.cmake

@@ -37,3 +37,5 @@ SET(CMAKE_PLATFORM_IMPLICIT_LINK_DIRECTORIES
   /lib /usr/lib /usr/lib32 /usr/lib64
   )
 
+# Enable use of lib64 search path variants by default.
+SET_PROPERTIES(GLOBAL PROPERTIES FIND_LIBRARY_USE_LIB64_PATHS TRUE)

Source/cmFindLibraryCommand.cxx

@@ -67,8 +67,14 @@ bool cmFindLibraryCommand::InitialPass(std::vector<std::string> const& argsIn)
       }
     return true;
     }
+
+  if(this->Makefile->GetCMakeInstance()
+     ->GetPropertyAsBool("FIND_LIBRARY_USE_LIB64_PATHS"))
+    {
     // add special 64 bit paths if this is a 64 bit compile.
     this->AddLib64Paths();
+    }
+
   std::string library;
   for(std::vector<std::string>::iterator i = this->Names.begin();
       i != this->Names.end() ; ++i)

Source/cmake.cxx

@@ -2940,6 +2940,13 @@ void cmake::DefineProperties(cmake *cm)
      "platform supports shared libraries. Basically all current general "
      "general purpose OS do so, the exception are usually embedded systems "
      "with no or special OSs.");
+  cm->DefineProperty
+    ("FIND_LIBRARY_USE_LIB64_PATHS", cmProperty::GLOBAL,
+     "Whether FIND_LIBRARY should automatically search lib64 directories.",
+     "FIND_LIBRARY_USE_LIB64_PATHS is a boolean specifying whether the "
+     "FIND_LIBRARY command should automatically search the lib64 variant of "
+     "directories called lib in the search path when building 64-bit "
+     "binaries.");
 }