Test with Clang 3.9 and GCC 6 on OS X, instead of Clang 3.8 and GCC 5.
diff --git a/extras/scripts/postsubmit-helper.sh b/extras/scripts/postsubmit-helper.sh
index 51d4b46..3f65d06 100755
--- a/extras/scripts/postsubmit-helper.sh
+++ b/extras/scripts/postsubmit-helper.sh
@@ -47,6 +47,11 @@
     export CXX=clang++-3.8
     ;;
     
+clang-3.9)
+    export CC=clang-3.9
+    export CXX=clang++-3.9
+    ;;
+
 clang-default)
     export CC=clang
     export CXX=clang++
diff --git a/extras/scripts/travis_ci_install_osx.sh b/extras/scripts/travis_ci_install_osx.sh
index e841326..349aa64 100755
--- a/extras/scripts/travis_ci_install_osx.sh
+++ b/extras/scripts/travis_ci_install_osx.sh
@@ -28,11 +28,13 @@
 gcc-4.8)       install_brew_package homebrew/versions/gcc48 ;;
 gcc-4.9)       install_brew_package homebrew/versions/gcc49 ;;
 gcc-5)         install_brew_package homebrew/versions/gcc5 ;;
+gcc-6)         install_brew_package gcc ;;
 clang-default) ;;
 clang-3.5)     install_brew_package homebrew/versions/llvm35 --with-clang --with-libcxx;;
 clang-3.6)     install_brew_package homebrew/versions/llvm36 --with-clang --with-libcxx;;
 clang-3.7)     install_brew_package homebrew/versions/llvm37 --with-clang --with-libcxx;;
 clang-3.8)     install_brew_package homebrew/versions/llvm38 --with-clang --with-libcxx;;
+clang-3.9)     install_brew_package llvm --with-clang --with-libcxx;;
 *) echo "Compiler not supported: ${COMPILER}. See travis_ci_install_osx.sh"; exit 1 ;;
 esac
 
diff --git a/extras/scripts/travis_yml_generator.py b/extras/scripts/travis_yml_generator.py
index bdf8e4e..59d22ee 100755
--- a/extras/scripts/travis_yml_generator.py
+++ b/extras/scripts/travis_yml_generator.py
@@ -161,7 +161,7 @@
 # UBSan (aka '-fsanitize=undefined') is not supported in GCC 4.8.
 # ASan (aka '-fsanitize=address') doesn't work, due to https://llvm.org/bugs/show_bug.cgi?id=27310.
 add_osx_tests(compiler='gcc-4.8', asan=False, ubsan=False)
-add_osx_tests(compiler='gcc-5', smoke_tests=['DebugPlain'])
+add_osx_tests(compiler='gcc-6', smoke_tests=['DebugPlain'])
 # ASan/UBSan are disabled because it would hit errors like:
 # ld: file not found: [...]/libclang_rt.asan_osx_dynamic.dylib
 # ld: file not found: [...]/libclang_rt.ubsan_osx.a
@@ -170,7 +170,7 @@
 # ASan/UBSan are disabled because it would hit errors like:
 # ld: file not found: [...]/libclang_rt.asan_osx_dynamic.dylib
 # Not sure if that's a limitation of Clang 3.8 on OS X or just of the brew-provided binaries.
-add_osx_tests(compiler='clang-3.8', stl='libc++', asan=False, ubsan=False, smoke_tests=['DebugPlain'])
+add_osx_tests(compiler='clang-3.9', stl='libc++', asan=False, ubsan=False, smoke_tests=['DebugPlain'])
 
 # UBSan is disabled because AppleClang does not support -fsanitize=undefined.
 add_osx_tests(compiler='clang-default', xcode_version='7.1', stl='libc++', ubsan=False)