Export of internal Abseil changes

--
7a9e8d95f795be037aa2dce4e44809ad0166aaec by Samuel Benzaquen <sbenza@google.com>:

Make end() iterator be nullptr.
This makes the creation of and comparison with end() smaller and faster. `find()!=end()` becomes leaner.

PiperOrigin-RevId: 304681605

--
8f3024979446b391b79b1b60ada7d00a504d6aa6 by Derek Mauro <dmauro@google.com>:

Fix Bazel's distdir detection and prefer double brackets (bash recommendation)

PiperOrigin-RevId: 304615725

--
f1d709cb4b2b3743d548b814dd19602fb057a5e6 by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 304570545

--
2bbfa5bda52057e1938a96c286ad33ff64e535e0 by Gennadiy Rozental <rogeeff@google.com>:

Implement general storage case as aligned buffer.

Aside from eliminating dynamic memory allocation for flag storage, we also saving 11 bytes per int flag, 15 bytes per double and string flag.

PiperOrigin-RevId: 304511965

--
9e1aed2a95d7d060f8b906fe8c67fc3ba537b521 by Derek Mauro <dmauro@google.com>:

Use reserve to make a bad_alloc less likely in endian_test

This happened once and shouldn't have happened, so it was probably
just a flake, but might as well make this change.

PiperOrigin-RevId: 304505572

--
c2faf22ba2d4d66753390e6959494214895581f0 by Gennadiy Rozental <rogeeff@google.com>:

Use anonymous bit fields to enforce separation between const and mutable bit fields.

We also move init_control field (which is now safe) to save 8 bytes per flag (based on size_tester output)

PiperOrigin-RevId: 304505215

--
7ec51250a84bb03e826b3caad64431e91748186a by Krzysztof Kosiński <krzysio@google.com>:

Change the buffer size in AppendNumberUnit to constexpr.

PiperOrigin-RevId: 304492779

--
a6c8db1be4f421ea7b7c02f7a01b4f48bad61883 by Gennadiy Rozental <rogeeff@google.com>:

Add test cases for two word storage.

Some additional tests were added for other storage kinds as well. These came about after I started to look into a coverage output and noticed that some cases (like reading flag values via reflection) were not covered by this test at all. It does not make sense to just add tests for two word values, so I've covered other storage kinds as well.

PiperOrigin-RevId: 304432511

--
2644ecc32e1215cd6451efcb2f1054fd77e7c812 by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 304254681

--
4949a6b20c2bb4b9b2c811f439ccb893abc08df5 by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 304250274
GitOrigin-RevId: 7a9e8d95f795be037aa2dce4e44809ad0166aaec
Change-Id: I01623de87355bec5cf87cc5932a1ca44cade9aae

11 files changed, 49 insertions, 49 deletions

diff --git a/ci/cmake_install_test.sh b/ci/cmake_install_test.sh
index 4c748eb9..b31e4b8c 100755
--- a/ci/cmake_install_test.sh
+++ b/ci/cmake_install_test.sh
@@ -16,7 +16,7 @@
 
 set -euox pipefail
 
-if [ -z ${ABSEIL_ROOT:-} ]; then
+if [[ -z ${ABSEIL_ROOT:-} ]]; then
   ABSEIL_ROOT="$(realpath $(dirname ${0})/..)"
 fi
 
diff --git a/ci/linux_clang-latest_libcxx_asan_bazel.sh b/ci/linux_clang-latest_libcxx_asan_bazel.sh
index 03463e2e..88d2a97d 100755
--- a/ci/linux_clang-latest_libcxx_asan_bazel.sh
+++ b/ci/linux_clang-latest_libcxx_asan_bazel.sh
@@ -20,19 +20,19 @@
 
 set -euox pipefail
 
-if [ -z ${ABSEIL_ROOT:-} ]; then
+if [[ -z ${ABSEIL_ROOT:-} ]]; then
   ABSEIL_ROOT="$(realpath $(dirname ${0})/..)"
 fi
 
-if [ -z ${STD:-} ]; then
+if [[ -z ${STD:-} ]]; then
   STD="c++11 c++14 c++17"
 fi
 
-if [ -z ${COMPILATION_MODE:-} ]; then
+if [[ -z ${COMPILATION_MODE:-} ]]; then
   COMPILATION_MODE="fastbuild opt"
 fi
 
-if [ -z ${EXCEPTIONS_MODE:-} ]; then
+if [[ -z ${EXCEPTIONS_MODE:-} ]]; then
   EXCEPTIONS_MODE="-fno-exceptions -fexceptions"
 fi
 
@@ -41,7 +41,7 @@ readonly DOCKER_CONTAINER=${LINUX_CLANG_LATEST_CONTAINER}
 
 # USE_BAZEL_CACHE=1 only works on Kokoro.
 # Without access to the credentials this won't work.
-if [ ${USE_BAZEL_CACHE:-0} -ne 0 ]; then
+if [[ ${USE_BAZEL_CACHE:-0} -ne 0 ]]; then
   DOCKER_EXTRA_ARGS="--volume=${KOKORO_KEYSTORE_DIR}:/keystore:ro ${DOCKER_EXTRA_ARGS:-}"
   # Bazel doesn't track changes to tools outside of the workspace
   # (e.g. /usr/bin/gcc), so by appending the docker container to the
@@ -54,7 +54,7 @@ fi
 # Avoid depending on external sites like GitHub by checking --distdir for
 # external dependencies first.
 # https://docs.bazel.build/versions/master/guide.html#distdir
-if [ -z ${KOKORO_GFILE_DIR:-} && -d "${KOKORO_GFILE_DIR}/distdir" ]; then
+if [[ ${KOKORO_GFILE_DIR:-} ]] && [[ -d "${KOKORO_GFILE_DIR}/distdir" ]]; then
   DOCKER_EXTRA_ARGS="--volume=${KOKORO_GFILE_DIR}/distdir:/distdir:ro ${DOCKER_EXTRA_ARGS:-}"
   BAZEL_EXTRA_ARGS="--distdir=/distdir ${BAZEL_EXTRA_ARGS:-}"
 fi
diff --git a/ci/linux_clang-latest_libcxx_bazel.sh b/ci/linux_clang-latest_libcxx_bazel.sh
index 050a98c9..f344a588 100755
--- a/ci/linux_clang-latest_libcxx_bazel.sh
+++ b/ci/linux_clang-latest_libcxx_bazel.sh
@@ -20,19 +20,19 @@
 
 set -euox pipefail
 
-if [ -z ${ABSEIL_ROOT:-} ]; then
+if [[ -z ${ABSEIL_ROOT:-} ]]; then
   ABSEIL_ROOT="$(realpath $(dirname ${0})/..)"
 fi
 
-if [ -z ${STD:-} ]; then
+if [[ -z ${STD:-} ]]; then
   STD="c++11 c++14 c++17"
 fi
 
-if [ -z ${COMPILATION_MODE:-} ]; then
+if [[ -z ${COMPILATION_MODE:-} ]]; then
   COMPILATION_MODE="fastbuild opt"
 fi
 
-if [ -z ${EXCEPTIONS_MODE:-} ]; then
+if [[ -z ${EXCEPTIONS_MODE:-} ]]; then
   EXCEPTIONS_MODE="-fno-exceptions -fexceptions"
 fi
 
@@ -41,7 +41,7 @@ readonly DOCKER_CONTAINER=${LINUX_CLANG_LATEST_CONTAINER}
 
 # USE_BAZEL_CACHE=1 only works on Kokoro.
 # Without access to the credentials this won't work.
-if [ ${USE_BAZEL_CACHE:-0} -ne 0 ]; then
+if [[ ${USE_BAZEL_CACHE:-0} -ne 0 ]]; then
   DOCKER_EXTRA_ARGS="--volume=${KOKORO_KEYSTORE_DIR}:/keystore:ro ${DOCKER_EXTRA_ARGS:-}"
   # Bazel doesn't track changes to tools outside of the workspace
   # (e.g. /usr/bin/gcc), so by appending the docker container to the
@@ -54,7 +54,7 @@ fi
 # Avoid depending on external sites like GitHub by checking --distdir for
 # external dependencies first.
 # https://docs.bazel.build/versions/master/guide.html#distdir
-if [ -z ${KOKORO_GFILE_DIR:-} && -d "${KOKORO_GFILE_DIR}/distdir" ]; then
+if [[ ${KOKORO_GFILE_DIR:-} ]] && [[ -d "${KOKORO_GFILE_DIR}/distdir" ]]; then
   DOCKER_EXTRA_ARGS="--volume=${KOKORO_GFILE_DIR}/distdir:/distdir:ro ${DOCKER_EXTRA_ARGS:-}"
   BAZEL_EXTRA_ARGS="--distdir=/distdir ${BAZEL_EXTRA_ARGS:-}"
 fi
diff --git a/ci/linux_clang-latest_libcxx_tsan_bazel.sh b/ci/linux_clang-latest_libcxx_tsan_bazel.sh
index 2f5fb12d..f7238457 100755
--- a/ci/linux_clang-latest_libcxx_tsan_bazel.sh
+++ b/ci/linux_clang-latest_libcxx_tsan_bazel.sh
@@ -20,19 +20,19 @@
 
 set -euox pipefail
 
-if [ -z ${ABSEIL_ROOT:-} ]; then
+if [[ -z ${ABSEIL_ROOT:-} ]]; then
   ABSEIL_ROOT="$(realpath $(dirname ${0})/..)"
 fi
 
-if [ -z ${STD:-} ]; then
+if [[ -z ${STD:-} ]]; then
   STD="c++11 c++14 c++17"
 fi
 
-if [ -z ${COMPILATION_MODE:-} ]; then
+if [[ -z ${COMPILATION_MODE:-} ]]; then
   COMPILATION_MODE="fastbuild opt"
 fi
 
-if [ -z ${EXCEPTIONS_MODE:-} ]; then
+if [[ -z ${EXCEPTIONS_MODE:-} ]]; then
   EXCEPTIONS_MODE="-fno-exceptions -fexceptions"
 fi
 
@@ -41,7 +41,7 @@ readonly DOCKER_CONTAINER=${LINUX_CLANG_LATEST_CONTAINER}
 
 # USE_BAZEL_CACHE=1 only works on Kokoro.
 # Without access to the credentials this won't work.
-if [ ${USE_BAZEL_CACHE:-0} -ne 0 ]; then
+if [[ ${USE_BAZEL_CACHE:-0} -ne 0 ]]; then
   DOCKER_EXTRA_ARGS="--volume=${KOKORO_KEYSTORE_DIR}:/keystore:ro ${DOCKER_EXTRA_ARGS:-}"
   # Bazel doesn't track changes to tools outside of the workspace
   # (e.g. /usr/bin/gcc), so by appending the docker container to the
@@ -54,7 +54,7 @@ fi
 # Avoid depending on external sites like GitHub by checking --distdir for
 # external dependencies first.
 # https://docs.bazel.build/versions/master/guide.html#distdir
-if [ -z ${KOKORO_GFILE_DIR:-} && -d "${KOKORO_GFILE_DIR}/distdir" ]; then
+if [[ ${KOKORO_GFILE_DIR:-} ]] && [[ -d "${KOKORO_GFILE_DIR}/distdir" ]]; then
   DOCKER_EXTRA_ARGS="--volume=${KOKORO_GFILE_DIR}/distdir:/distdir:ro ${DOCKER_EXTRA_ARGS:-}"
   BAZEL_EXTRA_ARGS="--distdir=/distdir ${BAZEL_EXTRA_ARGS:-}"
 fi
diff --git a/ci/linux_clang-latest_libstdcxx_bazel.sh b/ci/linux_clang-latest_libstdcxx_bazel.sh
index 087f59ba..62696293 100755
--- a/ci/linux_clang-latest_libstdcxx_bazel.sh
+++ b/ci/linux_clang-latest_libstdcxx_bazel.sh
@@ -20,19 +20,19 @@
 
 set -euox pipefail
 
-if [ -z ${ABSEIL_ROOT:-} ]; then
+if [[ -z ${ABSEIL_ROOT:-} ]]; then
   ABSEIL_ROOT="$(realpath $(dirname ${0})/..)"
 fi
 
-if [ -z ${STD:-} ]; then
+if [[ -z ${STD:-} ]]; then
   STD="c++11 c++14 c++17"
 fi
 
-if [ -z ${COMPILATION_MODE:-} ]; then
+if [[ -z ${COMPILATION_MODE:-} ]]; then
   COMPILATION_MODE="fastbuild opt"
 fi
 
-if [ -z ${EXCEPTIONS_MODE:-} ]; then
+if [[ -z ${EXCEPTIONS_MODE:-} ]]; then
   EXCEPTIONS_MODE="-fno-exceptions -fexceptions"
 fi
 
@@ -41,7 +41,7 @@ readonly DOCKER_CONTAINER=${LINUX_CLANG_LATEST_CONTAINER}
 
 # USE_BAZEL_CACHE=1 only works on Kokoro.
 # Without access to the credentials this won't work.
-if [ ${USE_BAZEL_CACHE:-0} -ne 0 ]; then
+if [[ ${USE_BAZEL_CACHE:-0} -ne 0 ]]; then
   DOCKER_EXTRA_ARGS="--volume=${KOKORO_KEYSTORE_DIR}:/keystore:ro ${DOCKER_EXTRA_ARGS:-}"
   # Bazel doesn't track changes to tools outside of the workspace
   # (e.g. /usr/bin/gcc), so by appending the docker container to the
@@ -54,7 +54,7 @@ fi
 # Avoid depending on external sites like GitHub by checking --distdir for
 # external dependencies first.
 # https://docs.bazel.build/versions/master/guide.html#distdir
-if [ -z ${KOKORO_GFILE_DIR:-} && -d "${KOKORO_GFILE_DIR}/distdir" ]; then
+if [[ ${KOKORO_GFILE_DIR:-} ]] && [[ -d "${KOKORO_GFILE_DIR}/distdir" ]]; then
   DOCKER_EXTRA_ARGS="--volume=${KOKORO_GFILE_DIR}/distdir:/distdir:ro ${DOCKER_EXTRA_ARGS:-}"
   BAZEL_EXTRA_ARGS="--distdir=/distdir ${BAZEL_EXTRA_ARGS:-}"
 fi
diff --git a/ci/linux_gcc-4.9_libstdcxx_bazel.sh b/ci/linux_gcc-4.9_libstdcxx_bazel.sh
index 622ea84b..8e6540cf 100755
--- a/ci/linux_gcc-4.9_libstdcxx_bazel.sh
+++ b/ci/linux_gcc-4.9_libstdcxx_bazel.sh
@@ -20,19 +20,19 @@
 
 set -euox pipefail
 
-if [ -z ${ABSEIL_ROOT:-} ]; then
+if [[ -z ${ABSEIL_ROOT:-} ]]; then
   ABSEIL_ROOT="$(realpath $(dirname ${0})/..)"
 fi
 
-if [ -z ${STD:-} ]; then
+if [[ -z ${STD:-} ]]; then
   STD="c++11 c++14"
 fi
 
-if [ -z ${COMPILATION_MODE:-} ]; then
+if [[ -z ${COMPILATION_MODE:-} ]]; then
   COMPILATION_MODE="fastbuild opt"
 fi
 
-if [ -z ${EXCEPTIONS_MODE:-} ]; then
+if [[ -z ${EXCEPTIONS_MODE:-} ]]; then
   EXCEPTIONS_MODE="-fno-exceptions -fexceptions"
 fi
 
@@ -41,7 +41,7 @@ readonly DOCKER_CONTAINER=${LINUX_GCC_49_CONTAINER}
 
 # USE_BAZEL_CACHE=1 only works on Kokoro.
 # Without access to the credentials this won't work.
-if [ ${USE_BAZEL_CACHE:-0} -ne 0 ]; then
+if [[ ${USE_BAZEL_CACHE:-0} -ne 0 ]]; then
   DOCKER_EXTRA_ARGS="--volume=${KOKORO_KEYSTORE_DIR}:/keystore:ro ${DOCKER_EXTRA_ARGS:-}"
   # Bazel doesn't track changes to tools outside of the workspace
   # (e.g. /usr/bin/gcc), so by appending the docker container to the
@@ -54,7 +54,7 @@ fi
 # Avoid depending on external sites like GitHub by checking --distdir for
 # external dependencies first.
 # https://docs.bazel.build/versions/master/guide.html#distdir
-if [ -z ${KOKORO_GFILE_DIR:-} && -d "${KOKORO_GFILE_DIR}/distdir" ]; then
+if [[ ${KOKORO_GFILE_DIR:-} ]] && [[ -d "${KOKORO_GFILE_DIR}/distdir" ]]; then
   DOCKER_EXTRA_ARGS="--volume=${KOKORO_GFILE_DIR}/distdir:/distdir:ro ${DOCKER_EXTRA_ARGS:-}"
   BAZEL_EXTRA_ARGS="--distdir=/distdir ${BAZEL_EXTRA_ARGS:-}"
 fi
diff --git a/ci/linux_gcc-latest_libstdcxx_bazel.sh b/ci/linux_gcc-latest_libstdcxx_bazel.sh
index f7dbd199..337285b0 100755
--- a/ci/linux_gcc-latest_libstdcxx_bazel.sh
+++ b/ci/linux_gcc-latest_libstdcxx_bazel.sh
@@ -20,19 +20,19 @@
 
 set -euox pipefail
 
-if [ -z ${ABSEIL_ROOT:-} ]; then
+if [[ -z ${ABSEIL_ROOT:-} ]]; then
   ABSEIL_ROOT="$(realpath $(dirname ${0})/..)"
 fi
 
-if [ -z ${STD:-} ]; then
+if [[ -z ${STD:-} ]]; then
   STD="c++11 c++14 c++17"
 fi
 
-if [ -z ${COMPILATION_MODE:-} ]; then
+if [[ -z ${COMPILATION_MODE:-} ]]; then
   COMPILATION_MODE="fastbuild opt"
 fi
 
-if [ -z ${EXCEPTIONS_MODE:-} ]; then
+if [[ -z ${EXCEPTIONS_MODE:-} ]]; then
   EXCEPTIONS_MODE="-fno-exceptions -fexceptions"
 fi
 
@@ -41,7 +41,7 @@ readonly DOCKER_CONTAINER=${LINUX_GCC_LATEST_CONTAINER}
 
 # USE_BAZEL_CACHE=1 only works on Kokoro.
 # Without access to the credentials this won't work.
-if [ ${USE_BAZEL_CACHE:-0} -ne 0 ]; then
+if [[ ${USE_BAZEL_CACHE:-0} -ne 0 ]]; then
   DOCKER_EXTRA_ARGS="--volume=${KOKORO_KEYSTORE_DIR}:/keystore:ro ${DOCKER_EXTRA_ARGS:-}"
   # Bazel doesn't track changes to tools outside of the workspace
   # (e.g. /usr/bin/gcc), so by appending the docker container to the
@@ -54,7 +54,7 @@ fi
 # Avoid depending on external sites like GitHub by checking --distdir for
 # external dependencies first.
 # https://docs.bazel.build/versions/master/guide.html#distdir
-if [ -z ${KOKORO_GFILE_DIR:-} && -d "${KOKORO_GFILE_DIR}/distdir" ]; then
+if [[ ${KOKORO_GFILE_DIR:-} ]] && [[ -d "${KOKORO_GFILE_DIR}/distdir" ]]; then
   DOCKER_EXTRA_ARGS="--volume=${KOKORO_GFILE_DIR}/distdir:/distdir:ro ${DOCKER_EXTRA_ARGS:-}"
   BAZEL_EXTRA_ARGS="--distdir=/distdir ${BAZEL_EXTRA_ARGS:-}"
 fi
@@ -75,7 +75,7 @@ for std in ${STD}; do
         ${DOCKER_CONTAINER} \
         /bin/sh -c "
           cp -r /abseil-cpp-ro/* /abseil-cpp/
-          if [ -n \"${ALTERNATE_OPTIONS:-}\" ]; then
+          if [[ -n \"${ALTERNATE_OPTIONS:-}\" ]]; then
             cp ${ALTERNATE_OPTIONS:-} absl/base/options.h || exit 1
           fi
           /usr/local/bin/bazel test ... \
diff --git a/ci/linux_gcc-latest_libstdcxx_cmake.sh b/ci/linux_gcc-latest_libstdcxx_cmake.sh
index b5015449..db5f6918 100755
--- a/ci/linux_gcc-latest_libstdcxx_cmake.sh
+++ b/ci/linux_gcc-latest_libstdcxx_cmake.sh
@@ -22,15 +22,15 @@
 
 set -euox pipefail
 
-if [ -z ${ABSEIL_ROOT:-} ]; then
+if [[ -z ${ABSEIL_ROOT:-} ]]; then
   ABSEIL_ROOT="$(realpath $(dirname ${0})/..)"
 fi
 
-if [ -z ${ABSL_CMAKE_CXX_STANDARDS:-} ]; then
+if [[ -z ${ABSL_CMAKE_CXX_STANDARDS:-} ]]; then
   ABSL_CMAKE_CXX_STANDARDS="11 14 17"
 fi
 
-if [ -z ${ABSL_CMAKE_BUILD_TYPES:-} ]; then
+if [[ -z ${ABSL_CMAKE_BUILD_TYPES:-} ]]; then
   ABSL_CMAKE_BUILD_TYPES="Debug Release"
 fi
 
diff --git a/ci/linux_gcc_alpine_cmake.sh b/ci/linux_gcc_alpine_cmake.sh
index 4496f8d4..f57ab12b 100755
--- a/ci/linux_gcc_alpine_cmake.sh
+++ b/ci/linux_gcc_alpine_cmake.sh
@@ -22,15 +22,15 @@
 
 set -euox pipefail
 
-if [ -z ${ABSEIL_ROOT:-} ]; then
+if [[ -z ${ABSEIL_ROOT:-} ]]; then
   ABSEIL_ROOT="$(realpath $(dirname ${0})/..)"
 fi
 
-if [ -z ${ABSL_CMAKE_CXX_STANDARDS:-} ]; then
+if [[ -z ${ABSL_CMAKE_CXX_STANDARDS:-} ]]; then
   ABSL_CMAKE_CXX_STANDARDS="11 14 17"
 fi
 
-if [ -z ${ABSL_CMAKE_BUILD_TYPES:-} ]; then
+if [[ -z ${ABSL_CMAKE_BUILD_TYPES:-} ]]; then
   ABSL_CMAKE_BUILD_TYPES="Debug Release"
 fi
 
diff --git a/ci/macos_xcode_bazel.sh b/ci/macos_xcode_bazel.sh
index f5f2d759..738adf94 100755
--- a/ci/macos_xcode_bazel.sh
+++ b/ci/macos_xcode_bazel.sh
@@ -19,13 +19,13 @@
 
 set -euox pipefail
 
-if [ -z ${ABSEIL_ROOT:-} ]; then
+if [[ -z ${ABSEIL_ROOT:-} ]]; then
   ABSEIL_ROOT="$(realpath $(dirname ${0})/..)"
 fi
 
 # If we are running on Kokoro, check for a versioned Bazel binary.
 KOKORO_GFILE_BAZEL_BIN="bazel-2.0.0-darwin-x86_64"
-if [ ${KOKORO_GFILE_DIR:-} ] && [ -f ${KOKORO_GFILE_DIR}/${KOKORO_GFILE_BAZEL_BIN} ]; then
+if [[ ${KOKORO_GFILE_DIR:-} ]] && [[ -f ${KOKORO_GFILE_DIR}/${KOKORO_GFILE_BAZEL_BIN} ]]; then
   BAZEL_BIN="${KOKORO_GFILE_DIR}/${KOKORO_GFILE_BAZEL_BIN}"
   chmod +x ${BAZEL_BIN}
 else
@@ -41,7 +41,7 @@ echo "---------------"
 
 cd ${ABSEIL_ROOT}
 
-if [ -n "${ALTERNATE_OPTIONS:-}" ]; then
+if [[ -n "${ALTERNATE_OPTIONS:-}" ]]; then
   cp ${ALTERNATE_OPTIONS:-} absl/base/options.h || exit 1
 fi
 
diff --git a/ci/macos_xcode_cmake.sh b/ci/macos_xcode_cmake.sh
index a1f4a857..cf78e207 100755
--- a/ci/macos_xcode_cmake.sh
+++ b/ci/macos_xcode_cmake.sh
@@ -19,12 +19,12 @@
 
 set -euox pipefail
 
-if [ -z ${ABSEIL_ROOT:-} ]; then
+if [[ -z ${ABSEIL_ROOT:-} ]]; then
   ABSEIL_ROOT="$(dirname ${0})/.."
 fi
 ABSEIL_ROOT=$(realpath ${ABSEIL_ROOT})
 
-if [ -z ${ABSL_CMAKE_BUILD_TYPES:-} ]; then
+if [[ -z ${ABSL_CMAKE_BUILD_TYPES:-} ]]; then
   ABSL_CMAKE_BUILD_TYPES="Debug"
 fi