it works fine in IOS7 ,but failed to compile in IOS6

[JackZhangJack]

it works fine in IOS7 ,but failed to compile in IOS6.

compiled errors as follows:

Ld /Users/jackzhang/Library/Developer/Xcode/DerivedData/BulidMap-dkkjfeldvhljysennsxangpablwi/Build/Products/Debug-iphonesimulator/BulidMap.app/BulidMap normal i386
    cd /Users/jackzhang/Downloads/BulidMap
    setenv IPHONEOS_DEPLOYMENT_TARGET 6.0
    setenv PATH "/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin:/Applications/Xcode.app/Contents/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin"
    /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -arch i386 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator7.0.sdk -L/Users/jackzhang/Library/Developer/Xcode/DerivedData/BulidMap-dkkjfeldvhljysennsxangpablwi/Build/Products/Debug-iphonesimulator -F/Users/jackzhang/Library/Developer/Xcode/DerivedData/BulidMap-dkkjfeldvhljysennsxangpablwi/Build/Products/Debug-iphonesimulator -F/Users/jackzhang/Library/SDKs/ArcGIS -F/Users/jackzhang/Library/SDKs/ArcGIS/iOS -F/Users/jackzhang/Library/SDKs/ArcGIS/iOS/Samples -F/Users/jackzhang/Library/SDKs/ArcGIS/iOS/Samples/MapViewDemo -F/Users/jackzhang/Library/SDKs/ArcGIS/iOS/Samples/MapViewDemo/Classes -F/Users/jackzhang/Library/SDKs/ArcGIS/iOS/Samples/MapViewDemo/Resources-iPad -filelist /Users/jackzhang/Library/Developer/Xcode/DerivedData/BulidMap-dkkjfeldvhljysennsxangpablwi/Build/Intermediates/BulidMap.build/Debug-iphonesimulator/BulidMap.build/Objects-normal/i386/BulidMap.LinkFileList -Xlinker -objc_abi_version -Xlinker 2 -all_load -ObjC -framework ArcGIS -fobjc-arc -fobjc-link-runtime -Xlinker -no_implicit_dylibs -mios-simulator-version-min=6.0 -framework CoreGraphics -framework OpenGLES -framework MediaPlayer -framework SystemConfiguration -framework Security -lz -framework MobileCoreServices -lstdc++ -framework CoreText -framework QuartzCore -framework CoreLocation -framework AudioToolbox -lsqlite3 -lxml2 -framework CFNetwork -framework CoreTelephony -framework UIKit -framework Foundation -Xlinker -dependency_info -Xlinker /Users/jackzhang/Library/Developer/Xcode/DerivedData/BulidMap-dkkjfeldvhljysennsxangpablwi/Build/Intermediates/BulidMap.build/Debug-iphonesimulator/BulidMap.build/Objects-normal/i386/BulidMap_dependency_info.dat -o /Users/jackzhang/Library/Developer/Xcode/DerivedData/BulidMap-dkkjfeldvhljysennsxangpablwi/Build/Products/Debug-iphonesimulator/BulidMap.app/BulidMap

Undefined symbols for architecture i386:
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::find_last_of(char const*, unsigned long, unsigned long) const", referenced from:
      boost::filesystem::path::m_parent_path_end() const in ArcGIS(libArcGISRT-sim.a-i386-master.o)
      boost::filesystem::path::filename() const in ArcGIS(libArcGISRT-sim.a-i386-master.o)
      boost::filesystem::path::m_path_iterator_decrement(boost::filesystem::path::iterator&) in ArcGIS(libArcGISRT-sim.a-i386-master.o)
      Esri_runtimecore::Geodatabase::Transportation_network::Transportation_network(std::__1::shared_ptr<Esri_runtimecore::Geodatabase::Database>&, Esri_runtimecore::Geodatabase::Transportation_network_definition&&) in ArcGIS(libArcGISRT-sim.a-i386-master.o)
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::find_first_of(char const*, unsigned long, unsigned long) const", referenced from:
      (anonymous namespace)::root_directory_start(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, unsigned long) in ArcGIS(libArcGISRT-sim.a-i386-master.o)
      boost::filesystem::path::filename() const in ArcGIS(libArcGISRT-sim.a-i386-master.o)
      boost::filesystem::path::m_path_iterator_increment(boost::filesystem::path::iterator&) in ArcGIS(libArcGISRT-sim.a-i386-master.o)
      boost::filesystem::path::m_path_iterator_decrement(boost::filesystem::path::iterator&) in ArcGIS(libArcGISRT-sim.a-i386-master.o)
      Esri_runtimecore::Geocoding::(anonymous namespace)::normalize(boost::filesystem::path const&) in ArcGIS(libArcGISRT-sim.a-i386-master.o)
      Esri_runtimecore::Geodatabase::Database_cache::get_database(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in ArcGIS(libArcGISRT-sim.a-i386-master.o)
      Esri_runtimecore::Labeling::stack_string_if_needed(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >&, int) in ArcGIS(libArcGISRT-sim.a-i386-master.o)
      ...