build: revert back to C++11

There seem to be many poor souls stuck to C++11. Because we
don't really depend on C++14 features let's wait for a reason
to bump up the standard to C++17 or later.

Close: #619
Fix: #618
Fix: #615

Author: gjasny

.github/workflows/bazel-ci.yml

@@ -8,14 +8,6 @@ jobs:
     strategy:
       matrix:
         os: [macos-latest, ubuntu-latest, windows-latest]
-        include:
-          - os: macOS-latest
-            bazel_args: "--cxxopt=-std=c++14"
-          - os: ubuntu-latest
-            bazel_args: "--cxxopt=-std=c++14"
-          - os: windows-latest
-            bazel_args: "--cxxopt=/std:c++14"
-
     steps:
       - name: Checkout source
         uses: actions/checkout@v3
@@ -48,14 +40,14 @@ jobs:
         run: bazel test --config=ssl ${{ matrix.bazel_args }} --test_output=all //...
 
       - name: Build
-        run: bazel build ${{ matrix.bazel_args }} //...
+        run: bazel build //...
 
       - name: Test
         run: bazel test ${{ matrix.bazel_args }} --test_output=all //...
 
       - name: Scraping Test
         if: runner.os != 'Windows'
-        run: bazel test ${{ matrix.bazel_args }} --test_output=all //pull/tests/integration:scrape-test
+        run: bazel test --test_output=all //pull/tests/integration:scrape-test
 
       - name: Benchmark
-        run: bazel run ${{ matrix.bazel_args }} -c opt //core/benchmarks
+        run: bazel run -c opt //core/benchmarks

CMakeLists.txt

@@ -23,12 +23,12 @@ option(ENABLE_COMPRESSION "Enable gzip compression" ON)
 option(ENABLE_TESTING "Build tests" ON)
 option(USE_THIRDPARTY_LIBRARIES "Use 3rdParty submodules" ON)
 option(THIRDPARTY_CIVETWEB_WITH_SSL "Enable SSL support for embedded civetweb source code")
-option(OVERRIDE_CXX_STANDARD_FLAGS "Force building with -std=c++14 even if the CXXFLAGS are configured differently" ON)
+option(OVERRIDE_CXX_STANDARD_FLAGS "Force building with -std=c++11 even if the CXXFLAGS are configured differently" ON)
 option(GENERATE_PKGCONFIG "Generate and install pkg-config files" ${UNIX})
 option(RUN_IWYU "Run include-what-you-use" OFF)
 
 if(OVERRIDE_CXX_STANDARD_FLAGS)
-  set(CMAKE_CXX_STANDARD 14)
+  set(CMAKE_CXX_STANDARD 11)
   set(CMAKE_CXX_EXTENSIONS Off)
 endif()
 

README.md

@@ -92,7 +92,7 @@ int main() {
 
 ## Requirements
 
-Using `prometheus-cpp` requires a C++14 compliant compiler. It has been successfully tested with GNU GCC 7.4 on Ubuntu Bionic (18.04) and Visual Studio 2017.
+Using `prometheus-cpp` requires a C++11 compliant compiler. It has been successfully tested with GNU GCC 7.4 on Ubuntu Bionic (18.04) and Visual Studio 2017.
 
 ## Building
 
@@ -247,19 +247,19 @@ guidelines](https://chris.beams.io/posts/git-commit/).
 
 You can check out this repo and build the library using
 ``` bash
-bazel build --cxxopt=-std=c++14 //...
+bazel build //...
 ```
 
 Run the unit tests using
 ```
-bazel test --cxxopt=-std=c++14 //...
+bazel test //...
 ```
 
 There is also an integration test that
 uses [telegraf](https://github.com/influxdata/telegraf) to scrape a
 sample server. With telegraf installed, it can be run using
 ```
-bazel test --cxxopt=-std=c++14 //pull/tests/integration:scrape-test
+bazel test //pull/tests/integration:scrape-test
 ```
 
 ## Benchmarks

cmake/project-import-pkgconfig/CMakeLists.txt

@@ -2,7 +2,7 @@ cmake_minimum_required(VERSION 3.12 FATAL_ERROR)
 
 project(prometheus-cpp-import)
 
-set(CMAKE_CXX_STANDARD 14)
+set(CMAKE_CXX_STANDARD 11)
 
 find_package(PkgConfig REQUIRED)
 

core/CMakeLists.txt

@@ -20,7 +20,7 @@ add_library(${PROJECT_NAME}::core ALIAS core)
 
 target_compile_features(core
   PUBLIC
-    cxx_std_14
+    cxx_std_11
 )
 
 target_link_libraries(core

core/include/prometheus/detail/future_std.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#include <memory>
+#include <utility>
+
+namespace prometheus {
+namespace detail {
+
+// Remove as soon C++14 can be used.
+template <typename T, typename... Args>
+std::unique_ptr<T> make_unique(Args&&... args) {
+  return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
+}
+
+}  // namespace detail
+}  // namespace prometheus

core/include/prometheus/family.h

@@ -9,6 +9,7 @@
 #include "prometheus/client_metric.h"
 #include "prometheus/collectable.h"
 #include "prometheus/detail/core_export.h"
+#include "prometheus/detail/future_std.h"
 #include "prometheus/detail/utils.h"
 #include "prometheus/labels.h"
 #include "prometheus/metric_family.h"
@@ -110,7 +111,7 @@ class PROMETHEUS_CPP_CORE_EXPORT Family : public Collectable {
   /// \throw std::runtime_exception on invalid label names.
   template <typename... Args>
   T& Add(const Labels& labels, Args&&... args) {
-    return Add(labels, std::make_unique<T>(args...));
+    return Add(labels, detail::make_unique<T>(args...));
   }
 
   /// \brief Remove the given dimensional data.

core/src/family.cc

@@ -4,7 +4,6 @@
 #include <cassert>
 #include <map>
 #include <stdexcept>
-#include <type_traits>
 #include <utility>
 
 #include "prometheus/check_names.h"

core/src/registry.cc

@@ -2,11 +2,11 @@
 
 #include <algorithm>
 #include <iterator>
-#include <memory>
 #include <stdexcept>
 #include <tuple>
 
 #include "prometheus/counter.h"
+#include "prometheus/detail/future_std.h"
 #include "prometheus/gauge.h"
 #include "prometheus/histogram.h"
 #include "prometheus/info.h"
@@ -141,7 +141,7 @@ Family<T>& Registry::Add(const std::string& name, const std::string& help,
     throw std::invalid_argument("Family name already exists");
   }
 
-  auto family = std::make_unique<Family<T>>(name, help, labels);
+  auto family = detail::make_unique<Family<T>>(name, help, labels);
   auto& ref = *family;
   families.push_back(std::move(family));
   return ref;

core/tests/family_test.cc

@@ -7,6 +7,7 @@
 
 #include "prometheus/client_metric.h"
 #include "prometheus/counter.h"
+#include "prometheus/detail/future_std.h"
 #include "prometheus/histogram.h"
 #include "prometheus/labels.h"
 #include "prometheus/summary.h"
@@ -81,16 +82,16 @@ TEST(FamilyTest, add_twice) {
 
 TEST(FamilyTest, throw_on_invalid_metric_name) {
   auto create_family_with_invalid_name = []() {
-    return std::make_unique<Family<Counter>>("", "empty name", Labels{});
+    return detail::make_unique<Family<Counter>>("", "empty name", Labels{});
   };
   EXPECT_ANY_THROW(create_family_with_invalid_name());
 }
 
 TEST(FamilyTest, throw_on_invalid_constant_label_name) {
   auto create_family_with_invalid_labels = []() {
-    return std::make_unique<Family<Counter>>("total_requests",
-                                             "Counts all requests",
-                                             Labels{{"__invalid", "counter1"}});
+    return detail::make_unique<Family<Counter>>(
+        "total_requests", "Counts all requests",
+        Labels{{"__inavlid", "counter1"}});
   };
   EXPECT_ANY_THROW(create_family_with_invalid_labels());
 }
@@ -118,7 +119,8 @@ TEST(FamilyTest, query_family_if_metric_already_exists) {
 
 TEST(FamilyTest, reject_histogram_with_constant_le_label) {
   auto labels = Labels{{"le", "test"}};
-  EXPECT_ANY_THROW(std::make_unique<Family<Histogram>>("name", "help", labels));
+  EXPECT_ANY_THROW(
+      detail::make_unique<Family<Histogram>>("name", "help", labels));
 }
 
 TEST(FamilyTest, reject_histogram_with_le_label) {
@@ -129,7 +131,8 @@ TEST(FamilyTest, reject_histogram_with_le_label) {
 
 TEST(FamilyTest, reject_summary_with_constant_quantile_label) {
   auto labels = Labels{{"quantile", "test"}};
-  EXPECT_ANY_THROW(std::make_unique<Family<Summary>>("name", "help", labels));
+  EXPECT_ANY_THROW(
+      detail::make_unique<Family<Summary>>("name", "help", labels));
 }
 
 TEST(FamilyTest, reject_summary_with_quantile_label) {