diff --git a/.ci/azure-build.yml b/.ci/azure-build.yml
new file mode 100644
index 000000000..e6b37f8e8
--- /dev/null
+++ b/.ci/azure-build.yml
@@ -0,0 +1,11 @@
+steps:
+
+- task: CMake@1
+  inputs:
+    cmakeArgs: .. -DCLI11_SINGLE_FILE=$(cli11.single) -DCLI11_CXX_STD=$(cli11.std) -DCLI11_SINGLE_FILE_TESTS=$(cli11.single) -DCMAKE_BUILD_TYPE=$(cli11.build_type) $(cli11.options)
+  displayName: 'Configure'
+
+- script: cmake --build . $(cli11.threadopt)
+  displayName: 'Build'
+  workingDirectory: build
+
diff --git a/.ci/azure-cmake.yml b/.ci/azure-cmake.yml
new file mode 100644
index 000000000..59b6ceb32
--- /dev/null
+++ b/.ci/azure-cmake.yml
@@ -0,0 +1,16 @@
+steps:
+
+# Note that silkeh/clang does not include ca-certificates, so check the shasum for verification
+- bash: |
+    wget --no-check-certificate "https://cmake.org/files/v3.14/cmake-3.14.3-Linux-x86_64.tar.gz"
+    echo "29faa62fb3a0b6323caa3d9557e1a5f1205614c0d4c5c2a9917f16a74f7eff68  cmake-3.14.3-Linux-x86_64.tar.gz" | shasum -sca 256
+  displayName: Download CMake
+
+- task: ExtractFiles@1
+  inputs:
+    archiveFilePatterns: 'cmake*.tar.gz'
+    destinationFolder: 'cmake_program'
+    displayName: Extract CMake
+
+- bash: echo "##vso[task.prependpath]$(Build.SourcesDirectory)/cmake_program/cmake-3.14.3-Linux-x86_64/bin"
+  displayName: Add CMake to PATH
diff --git a/.ci/azure-steps.yml b/.ci/azure-steps.yml
deleted file mode 100644
index 3ac2b35c4..000000000
--- a/.ci/azure-steps.yml
+++ /dev/null
@@ -1,18 +0,0 @@
-steps:
-
-- checkout: self
-  fetchDepth: 50
-  submodules: true
-
-- task: CMake@1
-  inputs:
-    cmakeArgs: .. -DCLI12_SINGLE_FILE=ON -DCLI11_CXX_STD=14 -DCLI11_SINGLE_FILE_TESTS=ON -DCMAKE_BUILD_TYPE=Debug
-  displayName: 'Configure'
-
-- script: cmake --build . -j
-  displayName: 'Build'
-  workingDirectory: build
-
-- script: ctest --output-on-failure -C Debug
-  displayName: 'Test'
-  workingDirectory: build
diff --git a/.ci/azure-test.yml b/.ci/azure-test.yml
new file mode 100644
index 000000000..b56daa1ff
--- /dev/null
+++ b/.ci/azure-test.yml
@@ -0,0 +1,5 @@
+steps:
+
+- script: ctest --output-on-failure -C $(cli11.build_type)
+  displayName: 'Test'
+  workingDirectory: build
diff --git a/.ci/check_tidy.sh b/.ci/check_tidy.sh
deleted file mode 100755
index 505b68eb9..000000000
--- a/.ci/check_tidy.sh
+++ /dev/null
@@ -1,21 +0,0 @@
-#!/usr/bin/env bash
-
-echo -en "travis_fold:start:script.build\\r"
-echo "Building with tidy on..."
-set -evx
-
-mkdir -p build-tidy
-cd build-tidy
-CXX_FLAGS="-Werror -Wcast-align -Wfloat-equal -Wimplicit-atomic-properties -Wmissing-declarations -Woverlength-strings -Wshadow -Wstrict-selector-match -Wundeclared-selector -Wunreachable-code -std=c++11" cmake .. -DCLANG_TIDY_FIX=ON
-cmake --build .
-
-set -evx
-echo -en "travis_fold:end:script.build\\r"
-echo -en "travis_fold:start:script.compare\\r"
-echo "Checking git diff..."
-set -evx
-
-git diff --exit-code --color
-
-set +evx
-echo -en "travis_fold:end:script.compare\\r"
diff --git a/.editorconfig b/.editorconfig
index 35463abd0..979b04950 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -7,3 +7,5 @@ insert_final_newline = true
 end_of_line = lf
 trim_trailing_whitespace = true
 
+[*.yml]
+indent_size = 2
diff --git a/.travis.yml b/.travis.yml
index 78e1f02f5..fb7d17ff7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -23,15 +23,6 @@ matrix:
     - .ci/make_and_test.sh 14
     - .ci/make_and_test.sh 17
 
-    # Check style/tidy
-  - compiler: clang
-    env:
-    - CHECK_STYLE=yes
-    script:
-    - cd "${TRAVIS_BUILD_DIR}"
-    - scripts/check_style.sh
-    - .ci/check_tidy.sh
-
     # Docs and clang 3.5
   - compiler: clang
     env:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index bbdc1b39e..c5bd6b7b7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,8 @@ Set handling has been completely replaced by a new backend that works as a Valid
 * Cleanup for shadow warnings [#232]
 * Better alignment on multiline descriptions [#269]
 * Better support for aarch64 [#266]
+* Respect `BUILD_TESTING` only if CLI11 is the main project; otherwise, `CLI11_TESTING` must be used [#277]
+* Drop auto-detection of experimental optional; must be enabled explicitly (too fragile) [#277]
 
 > ### Converting from CLI11 1.7:
 >
@@ -54,6 +56,7 @@ Set handling has been completely replaced by a new backend that works as a Valid
 [#265]: https://github.com/CLIUtils/CLI11/pull/265
 [#266]: https://github.com/CLIUtils/CLI11/pull/266
 [#269]: https://github.com/CLIUtils/CLI11/pull/269
+[#277]: https://github.com/CLIUtils/CLI11/pull/277
 
 
 ## Version 1.7.1: Quick patch
@@ -85,7 +88,7 @@ Passing the same subcommand multiple times is better supported. Several new feat
 * Parsing is now done in phases: `shortcurcuits`, `ini`, `env`, `callbacks`, and `requirements`; all subcommands complete a phase before moving on. [#179]
 * Calling parse multiple times is now officially supported without `clear` (automatic). [#179]
 * Dropped the mostly undocumented `short_circuit` property, as help flag parsing is a bit more complex, and the default callback behavior of options now works properly. [#179]
-* Use the standard `BUILD_TESTING` over `CLI11_TESTING` if defined (`CLI11_TESTING` may eventually be removed) [#183]
+* Use the standard `BUILD_TESTING` over `CLI11_TESTING` if defined [#183]
 * Cleanup warnings [#191]
 * Remove deprecated names: `set_footer`, `set_name`, `set_callback`, and `set_type_name`. Use without the `set_` instead. [#192]
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6dc6df558..8b950705b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2,12 +2,13 @@ cmake_minimum_required(VERSION 3.4)
 # Note: this is a header only library. If you have an older CMake than 3.4,
 # just add the CLI11/include directory and that's all you need to do.
 
-# Make sure users don't get warnings on a tested (3.4 to 3.13) version
+# Make sure users don't get warnings on a tested (3.4 to 3.14) version
 # of CMake. For most of the policies, the new version is better (hence the change).
-if(${CMAKE_VERSION} VERSION_LESS 3.13)
+# We don't use the 3.4...3.14 syntax because of a bug in a version of MSVC
+if(${CMAKE_VERSION} VERSION_LESS 3.14)
     cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-    cmake_policy(VERSION 3.13)
+    cmake_policy(VERSION 3.14)
 endif()
 
 set(VERSION_REGEX "#define CLI11_VERSION[ \t]+\"(.+)\"")
@@ -27,6 +28,15 @@ if(CMAKE_PROJECT_NAME STREQUAL PROJECT_NAME)
     # User settable
     set(CLI11_CXX_STD "11"  CACHE STRING "The CMake standard to require")
 
+    # Special override for Clang on Linux (useful with an old stdlibc++ and a newer clang)
+    if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+        option(CLI11_FORCE_LIBCXX "Force Clang to use libc++ instead of libstdc++ (Linux only)" OFF)
+        if(CLI11_FORCE_LIBCXX)
+            set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++")
+            set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -stdlib=libc++")
+        endif()
+    endif()
+
     set(CUR_PROJ ON)
     set(CMAKE_CXX_STANDARD ${CLI11_CXX_STD})
     set(CMAKE_CXX_EXTENSIONS OFF)
@@ -149,14 +159,23 @@ if(CLI11_SINGLE_FILE)
     target_include_directories(CLI11_SINGLE INTERFACE "${CMAKE_CURRENT_BINARY_DIR}/include/")
 endif()
 
-cmake_dependent_option(CLI11_SINGLE_FILE_TESTS "Duplicate all the tests for a single file build" OFF "CLI11_SINGLE_FILE" OFF)
+cmake_dependent_option(CLI11_SINGLE_FILE_TESTS
+    "Duplicate all the tests for a single file build"
+    OFF
+    "CLI11_SINGLE_FILE"
+    OFF)
 
-cmake_dependent_option(CLI11_TESTING "Build the tests and add them" ON "CUR_PROJ" OFF)
-if(DEFINED BUILD_TESTING)
-    cmake_dependent_option(CLI11_TESTING "" ON "BUILD_TESTING" OFF)
-    message(STATUS "BUILD_TESTING is defined and it supersedes CLI11_TESTING. Has forced to ${CLI11_TESTING}")
+
+if(DEFINED CLI11_TESTING)
+    set(CLI11_TESTING_INTERNAL "${CLI11_TESTING}")
+elseif(CUR_PROJ)
+    option(BUILD_TESTING "Build the tests" ON)
+    set(CLI11_TESTING_INTERNAL "${BUILD_TESTING}")
+else()
+    set(CLI11_TESTING_INTERNAL OFF)
 endif()
-if(CLI11_TESTING)
+
+if(CLI11_TESTING_INTERNAL)
     enable_testing()
     add_subdirectory(tests)
 endif()
diff --git a/README.md b/README.md
index 3e4d22f14..dd7173009 100644
--- a/README.md
+++ b/README.md
@@ -73,7 +73,7 @@ An acceptable CLI parser library should be all of the following:
 
 -   Easy to include (i.e., header only, one file if possible, **no external requirements**).
 -   Short, simple syntax: This is one of the main reasons to use a CLI parser, it should make variables from the command line nearly as easy to define as any other variables. If most of your program is hidden in CLI parsing, this is a problem for readability.
--   C++11 or better: Should work with GCC 4.8+ (default on CentOS/RHEL 7), Clang 3.5+, AppleClang 7+, NVCC 7.0+, or MSVC 2015+.
+-   C++11 or better: Should work with GCC 4.8+ (default on CentOS/RHEL 7), Clang 3.4+, AppleClang 7+, NVCC 7.0+, or MSVC 2015+.
 -   Work on Linux, macOS, and Windows.
 -   Well tested using [Travis][] (Linux) and [AppVeyor][] (Windows) or [Azure][] (all three). "Well" is defined as having good coverage measured by [CodeCov][].
 -   Clear help printing.
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 328bbc3e3..0c2f5bafb 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -6,21 +6,71 @@
 trigger:
 - master
 
+variables:
+  cli11.single: ON
+  cli11.std: 14
+  cli11.build_type: Debug
+  cli11.options:
+  cli11.threadopt: -j
+
 jobs:
-- job: Linux
+
+- job: ClangFormatTidy
+  variables:
+    CXX_FLAGS: "-Werror -Wcast-align -Wfloat-equal -Wimplicit-atomic-properties -Wmissing-declarations -Woverlength-strings -Wshadow -Wstrict-selector-match -Wundeclared-selector -Wunreachable-code -std=c++11"
+    cli11.options: -DCLANG_TIDY_FIX=ON
+    cli11.std: 11
+    cli11.single: OFF
+    cli11.threadopt:
   pool:
     vmImage: 'ubuntu-16.04'
+  container: silkeh/clang:5
   steps:
-    - template: .ci/azure-steps.yml
+    - script: scripts/check_style.sh
+      displayName: Check format
+    - template: .ci/azure-cmake.yml
+    - template: .ci/azure-build.yml
+    - script: git diff --exit-code --color
+      displayName: Check tidy
 
-- job: macOS
+- job: Native
+  strategy:
+    matrix:
+      Linux:
+        vmImage: 'ubuntu-16.04'
+      macOS:
+        vmImage: 'macOS-10.14'
+      Windows:
+        vmImage: 'vs2017-win2016'
   pool:
-    vmImage: 'macOS-10.13'
+    vmImage: $(vmImage)
   steps:
-    - template: .ci/azure-steps.yml
+    - template: .ci/azure-build.yml
+    - template: .ci/azure-test.yml
 
-- job: Windows
+- job: Docker
+  variables:
+    cli11.single: OFF
   pool:
-    vmImage: 'vs2017-win2016'
+    vmImage: 'ubuntu-16.04'
+  strategy:
+    matrix:
+      gcc9:
+        containerImage: gcc:9
+        cli11.std: 17
+      gcc4.7:
+        containerImage: gcc:4.7
+        cli11.std: 11
+      clang3.4:
+        containerImage: silkeh/clang:3.4
+        cli11.std: 11
+      clang8:
+        containerImage: silkeh/clang:8
+        cli11.std: 14
+        cli11.options: -DCLI11_FORCE_LIBCXX=ON
+  container: $[ variables['containerImage'] ]
   steps:
-    - template: .ci/azure-steps.yml
+    - template: .ci/azure-cmake.yml
+    - template: .ci/azure-build.yml
+    - template: .ci/azure-test.yml
+
diff --git a/include/CLI/Optional.hpp b/include/CLI/Optional.hpp
index f3212671e..6e60fb606 100644
--- a/include/CLI/Optional.hpp
+++ b/include/CLI/Optional.hpp
@@ -19,11 +19,7 @@
 #define CLI11_STD_OPTIONAL 0
 #endif
 
-#if defined(CLI11_CPP14) && __has_include(<experimental/optional>) && \
-    !defined(CLI11_EXPERIMENTAL_OPTIONAL) \
-    && (!defined(CLI11_STD_OPTIONAL) || CLI11_STD_OPTIONAL == 0)
-#define CLI11_EXPERIMENTAL_OPTIONAL 1
-#elif !defined(CLI11_EXPERIMENTAL_OPTIONAL)
+#if !defined(CLI11_EXPERIMENTAL_OPTIONAL)
 #define CLI11_EXPERIMENTAL_OPTIONAL 0
 #endif
 
diff --git a/include/CLI/Timer.hpp b/include/CLI/Timer.hpp
index 61039c2cd..0a82dbcff 100644
--- a/include/CLI/Timer.hpp
+++ b/include/CLI/Timer.hpp
@@ -9,6 +9,7 @@
 #define _GLIBCXX_USE_NANOSLEEP
 #endif
 
+#include <array>
 #include <chrono>
 #include <functional>
 #include <iostream>
@@ -86,9 +87,9 @@ class Timer {
     /// This prints out a time string from a time
     std::string make_time_str(double time) const {
         auto print_it = [](double x, std::string unit) {
-            char buffer[50];
-            std::snprintf(buffer, 50, "%.5g", x);
-            return buffer + std::string(" ") + unit;
+            std::array<char, 50> buffer;
+            std::snprintf(buffer.data(), 50, "%.5g", x);
+            return buffer.data() + std::string(" ") + unit;
         };
 
         if(time < .000001)
diff --git a/scripts/check_style_docker.sh b/scripts/check_style_docker.sh
index 9030dc51e..3defb2406 100755
--- a/scripts/check_style_docker.sh
+++ b/scripts/check_style_docker.sh
@@ -1,12 +1,13 @@
 #!/usr/bin/env sh
 
 # Also good but untagged: CLANG_FORMAT=unibeautify/clang-format
+# This might provide more control in the future: silkeh/clang:8 (etc)
 CLANG_FORMAT=saschpe/clang-format:5.0.1
 
 set -evx
 
-docker run --rm -it ${CLANG_FORMAT} --version
-docker run --rm -it -v "$(pwd)":/workdir -w /workdir ${CLANG_FORMAT} -style=file -sort-includes -i $(git ls-files -- '*.cpp' '*.hpp')
+docker run --rm ${CLANG_FORMAT} --version
+docker run --rm --user $(id -u):$(id -g) -v "$(pwd)":/workdir -w /workdir ${CLANG_FORMAT} -style=file -sort-includes -i $(git ls-files -- '*.cpp' '*.hpp')
 
 git diff --exit-code --color