Use the clang 3.4 release tarball instead of apt for clang 3.4.

It appears the llvm.org/apt/ repository isn't always reliable.  So let's
use the release tarball instead.  Also, make using 3.4 conditional, so
we can use the clang 3.3 if things still manage to go awry in the
future.  Note: using 3.3 means that we won't get leak detection.

I left the logic for using llvm.org/apt/, just in case we want try using
it again sometime.

scripts/travis-setup.sh

@@ -1,19 +1,44 @@
 #!/bin/sh -e
 
+# Despite the logs, CC isn't being exported at before_install time in Travis.
+# So the following check cannot be used to avoid the download.
 # [ "$CC" != "clang" ] && exit
 
-add-apt-repository -y ppa:ubuntu-toolchain-r/ppa
-wget -O - http://llvm.org/apt/llvm-snapshot.gpg.key | apt-key add -
+echo "Downloading clang 3.4..."
+mkdir /usr/local/clang-3.4
+wget -q -O - http://llvm.org/releases/3.4/clang+llvm-3.4-x86_64-unknown-ubuntu12.04.tar.xz |
+	unxz -c | tar xf - --strip-components=1 -C /usr/local/clang-3.4
 
-cat > /etc/apt/sources.list.d/clang.list << "EOF"
-deb http://llvm.org/apt/precise/ llvm-toolchain-precise main
-# deb-src http://llvm.org/apt/precise/ llvm-toolchain-precise main
-# 3.4
-deb http://llvm.org/apt/precise/ llvm-toolchain-precise-3.4 main
-# deb-src http://llvm.org/apt/precise/ llvm-toolchain-precise-3.4 main
-# Common
-deb http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu precise main
-EOF
 
-apt-get -qq update
-apt-get -qq -y --no-install-recommends install clang-3.4 lldb-3.4
+# The section below is still around, in case we want to try the llvm.org/apt/
+# repository again.
+
+# Set to true to enable using the clang stable builds hosted at
+# http://llvm.org/apt/.
+#
+# Note: there have been issues with this repository.  Several days in a row
+# there have been problems running from broken a source repository (causing us
+# to remove them from the .list file), to the toolchain being packaged
+# incorrectly (most likely due to a change in version number--3.4.0 -> 3.4.1).
+# Use with care.
+# USE_CLANG_34=true
+
+# if [ -n "$USE_CLANG_34" ]; then
+# 	add-apt-repository -y ppa:ubuntu-toolchain-r/ppa
+# 	wget -O - http://llvm.org/apt/llvm-snapshot.gpg.key | apt-key add -
+
+# 	cat > /etc/apt/sources.list.d/clang.list << "EOF"
+# # deb http://llvm.org/apt/precise/ llvm-toolchain-precise main
+# # deb-src http://llvm.org/apt/precise/ llvm-toolchain-precise main
+# # 3.4
+# deb http://llvm.org/apt/precise/ llvm-toolchain-precise-3.4 main
+# # deb-src http://llvm.org/apt/precise/ llvm-toolchain-precise-3.4 main
+# # Common
+# deb http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu precise main
+# EOF
+# fi
+
+# apt-get -qq update
+
+# [ -n "$USE_CLANG_34" ] &&
+# 	apt-get -qq -y --no-install-recommends install clang-3.4 lldb-3.4

scripts/travis.sh

@@ -26,8 +26,18 @@ check_and_report() {
 MAKE_CMD="make -j2"
 
 if [ "$CC" = "clang" ]; then
-	# force using the version installed by 'travis-setup.sh'
-	export CC=/usr/bin/clang
+	if test -f /usr/local/clang-3.4/bin/clang; then
+		USE_CLANG_34=true
+		export CC=/usr/local/clang-3.4/bin/clang
+		symbolizer=/usr/local/clang-3.4/bin/llvm-symbolizer
+	fi
+
+	# Try to detect clang-3.4 installed via apt and through llvm.org/apt/.
+	if dpkg -s clang-3.4 > /dev/null 2>&1; then
+		USE_CLANG_34=true
+		export CC=/usr/bin/clang
+		symbolizer=/usr/bin/llvm-symbolizer-3.4
+	fi
 
 	install_dir="$(pwd)/dist"
 	# temporary directory for writing sanitizer logs
@@ -36,13 +46,18 @@ if [ "$CC" = "clang" ]; then
 	mkdir -p "$tmpdir"
 
 	# need the symbolizer path for stack traces with source information
-	symbolizer=/usr/bin/llvm-symbolizer-3.4
+	if [ -n "$USE_CLANG_34" ]; then
+		export ASAN_OPTIONS="detect_leaks=1:"
+	else
+		symbolizer=/usr/local/clang-3.3/bin/llvm-symbolizer
+        fi
 
-	export SKIP_UNITTEST=1
 	export SANITIZE=1
 	export ASAN_SYMBOLIZER_PATH=$symbolizer
-	export ASAN_OPTIONS="detect_leaks=1:log_path=$tmpdir/asan"
+	export ASAN_OPTIONS="${ASAN_OPTIONS}log_path=$tmpdir/asan"
 	export TSAN_OPTIONS="external_symbolizer_path=$symbolizer:log_path=$tmpdir/tsan"
+
+	export SKIP_UNITTEST=1
 	export UBSAN_OPTIONS="log_path=$tmpdir/ubsan" # not sure if this works
 
 	$MAKE_CMD cmake CMAKE_EXTRA_FLAGS="-DCMAKE_INSTALL_PREFIX=$install_dir"