[BUILD] Need fine-grained HAVE_CPP_STDLIB (#2304)

.github/workflows/ci.yml

@@ -316,6 +316,42 @@ jobs:
         CXX: /usr/bin/g++-4.8
       run: ./ci/do_ci.sh cmake.legacy.exporter.otprotocol.test
 
+  cmake_test_cxx14_gcc:
+    name: CMake C++14 test(GCC)
+    runs-on: ubuntu-20.04
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        submodules: 'recursive'
+    - name: setup
+      env:
+        CMAKE_VERSION: 3.20.6
+      run: |
+        sudo -E ./ci/setup_ci_environment.sh
+        sudo -E ./ci/setup_cmake.sh
+    - name: run tests (enable stl)
+      env:
+        CXX_STANDARD: '14'
+      run: ./ci/do_ci.sh cmake.c++14.stl.test
+
+  cmake_test_cxx17_gcc:
+    name: CMake C++17 test(GCC)
+    runs-on: ubuntu-20.04
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        submodules: 'recursive'
+    - name: setup
+      env:
+        CMAKE_VERSION: 3.20.6
+      run: |
+        sudo -E ./ci/setup_ci_environment.sh
+        sudo -E ./ci/setup_cmake.sh
+    - name: run tests (enable stl)
+      env:
+        CXX_STANDARD: '17'
+      run: ./ci/do_ci.sh cmake.c++17.stl.test
+
   cmake_test_cxx20_gcc:
     name: CMake C++20 test(GCC)
     runs-on: ubuntu-20.04

CHANGELOG.md

@@ -24,6 +24,29 @@ Increment the:
 * [EXPORTER] Replace colons with underscores when converting to Prometheus label
   [#2324](https://github.com/open-telemetry/opentelemetry-cpp/pull/2330)
 
+Breaking changes:
+
+* [BUILD] Need fine-grained HAVE_CPP_STDLIB
+  [#2304](https://github.com/open-telemetry/opentelemetry-cpp/pull/2304)
+  * In `CMAKE`, the boolean option `WITH_STL` as changed to an option
+    that accepts the values `OFF`, `ON`, `CXX11`, `CXX14`, `CXX17`,
+    `CXX20` and `CXX23`.
+  * Applications makefiles that did not set WITH_STL need to use
+    `WITH_STL=OFF` instead (this is the default).
+  * Applications makefiles that did set WITH_STL need to use
+    `WITH_STL=ON` instead, or may choose to pick a specific value.
+  * In the `API` header files, the preprocessor symbol `HAVE_CPP_STDLIB`
+    is no longer used.
+  * Applications that did set `HAVE_CPP_STDLIB` before, need to set
+    `OPENTELEMETRY_STL_VERSION=<version>` instead, to build with a
+    specific STL version (2011, 2014, 2017, 2020, 2023).
+  * The opentelemetry-cpp makefile no longer sets
+    CMAKE_CXX_STANDARD by itself.
+    Instead, the CMAKE_CXX_STANDARD and/or compiler options -stdc++ used
+    by the caller are honored.
+  * Applications that set neither CMAKE_CXX_STANDARD nor -stdc++
+    options may need to provide a C++ standard in their makefiles.
+
 ## [1.11.0] 2023-08-21
 
 * [BUILD] Fix more cases for symbol name for 32-bit win32 DLL build

CMakeLists.txt

@@ -154,7 +154,10 @@ message(STATUS "OPENTELEMETRY_VERSION=${OPENTELEMETRY_VERSION}")
 
 option(WITH_NO_DEPRECATED_CODE "Do not include deprecated code" OFF)
 
-option(WITH_STL "Whether to use Standard Library for C++ latest features" OFF)
+set(WITH_STL
+    "OFF"
+    CACHE STRING "Which version of the Standard Library for C++ to use")
+
 option(WITH_GSL
        "Whether to use Guidelines Support Library for C++ latest features" OFF)
 
@@ -169,22 +172,7 @@ option(OPENTELEMETRY_INSTALL "Whether to install opentelemetry targets"
 
 include("${PROJECT_SOURCE_DIR}/cmake/tools.cmake")
 
-if(NOT DEFINED CMAKE_CXX_STANDARD)
-  if(WITH_STL)
-    # Require at least C++17. C++20 is needed to avoid gsl::span
-    if(CMAKE_VERSION VERSION_GREATER 3.11.999)
-      # Ask for 20, may get anything below
-      set(CMAKE_CXX_STANDARD 20)
-    else()
-      # Ask for 17, may get anything below
-      set(CMAKE_CXX_STANDARD 17)
-    endif()
-  else()
-    set(CMAKE_CXX_STANDARD 11)
-  endif()
-endif()
-
-if(WITH_STL)
+if(NOT WITH_STL STREQUAL "OFF")
   # These definitions are needed for test projects that do not link against
   # opentelemetry-api library directly. We ensure that variant implementation
   # (absl::variant or std::variant) in variant unit test code is consistent with

api/CMakeLists.txt

@@ -51,11 +51,36 @@ if(WITH_ABSEIL)
        "absl_bits" "absl_city")
 endif()
 
-if(WITH_STL)
-  message("Building with standard library types...")
-  target_compile_definitions(opentelemetry_api INTERFACE HAVE_CPP_STDLIB)
+if(WITH_STL STREQUAL "OFF")
+  message(STATUS "Building WITH_STL=OFF")
+elseif(WITH_STL STREQUAL "CXX11")
+  message(STATUS "Building WITH_STL=CXX11")
+  target_compile_definitions(opentelemetry_api
+                             INTERFACE OPENTELEMETRY_STL_VERSION=2011)
+elseif(WITH_STL STREQUAL "CXX14")
+  message(STATUS "Building WITH_STL=CXX14")
+  target_compile_definitions(opentelemetry_api
+                             INTERFACE OPENTELEMETRY_STL_VERSION=2014)
+elseif(WITH_STL STREQUAL "CXX17")
+  message(STATUS "Building WITH_STL=CXX17")
+  target_compile_definitions(opentelemetry_api
+                             INTERFACE OPENTELEMETRY_STL_VERSION=2017)
+elseif(WITH_STL STREQUAL "CXX20")
+  message(STATUS "Building WITH_STL=CXX20")
+  target_compile_definitions(opentelemetry_api
+                             INTERFACE OPENTELEMETRY_STL_VERSION=2020)
+elseif(WITH_STL STREQUAL "CXX23")
+  message(STATUS "Building WITH_STL=CXX23")
+  target_compile_definitions(opentelemetry_api
+                             INTERFACE OPENTELEMETRY_STL_VERSION=2023)
+elseif(WITH_STL STREQUAL "ON")
+  message(STATUS "Building WITH_STL=ON")
+  # "ON" corresponds to "CXX23" at this time.
+  target_compile_definitions(opentelemetry_api
+                             INTERFACE OPENTELEMETRY_STL_VERSION=2023)
 else()
-  message("Building with nostd types...")
+  message(
+    FATAL_ERROR "WITH_STL must be ON, OFF, CXX11, CXX14, CXX17, CXX20 or CXX23")
 endif()
 
 if(WITH_GSL)

api/include/opentelemetry/nostd/shared_ptr.h

@@ -2,9 +2,15 @@
 // SPDX-License-Identifier: Apache-2.0
 
 #pragma once
-#ifdef HAVE_CPP_STDLIB
-#  include "opentelemetry/std/shared_ptr.h"
-#else
+
+#if defined(OPENTELEMETRY_STL_VERSION)
+#  if OPENTELEMETRY_STL_VERSION >= 2011
+#    include "opentelemetry/std/shared_ptr.h"
+#    define OPENTELEMETRY_HAVE_STD_SHARED_PTR
+#  endif
+#endif
+
+#if !defined(OPENTELEMETRY_HAVE_STD_SHARED_PTR)
 #  include <cstdlib>
 #  include <memory>
 #  include <utility>
@@ -201,4 +207,4 @@ inline bool operator!=(std::nullptr_t, const shared_ptr<T> &rhs) noexcept
 }
 }  // namespace nostd
 OPENTELEMETRY_END_NAMESPACE
-#endif
+#endif /* OPENTELEMETRY_HAVE_STD_SHARED_PTR */

api/include/opentelemetry/nostd/span.h

@@ -4,32 +4,34 @@
 #pragma once
 
 // Try to use either `std::span` or `gsl::span`
-#ifdef HAVE_CPP_STDLIB
-#  include <array>
-#  include <cstddef>
-#  include <iterator>
-#  include <type_traits>
+#if defined(OPENTELEMETRY_STL_VERSION)
+#  if OPENTELEMETRY_STL_VERSION >= 2020
+#    include <array>
+#    include <cstddef>
+#    include <iterator>
+#    include <type_traits>
 
 /**
  * @brief Clang 14.0.0 with libc++ do not support implicitly construct a span
  * for a range. We just use our fallback version.
  *
  */
-#  if !defined(OPENTELEMETRY_OPTION_USE_STD_SPAN) && defined(_LIBCPP_VERSION)
-#    if _LIBCPP_VERSION <= 14000
-#      define OPENTELEMETRY_OPTION_USE_STD_SPAN 0
+#    if !defined(OPENTELEMETRY_OPTION_USE_STD_SPAN) && defined(_LIBCPP_VERSION)
+#      if _LIBCPP_VERSION <= 14000
+#        define OPENTELEMETRY_OPTION_USE_STD_SPAN 0
+#      endif
 #    endif
-#  endif
-#  ifndef OPENTELEMETRY_OPTION_USE_STD_SPAN
-#    define OPENTELEMETRY_OPTION_USE_STD_SPAN 1
-#  endif
-#  if OPENTELEMETRY_OPTION_USE_STD_SPAN
-#    include "opentelemetry/std/span.h"
-#  endif
-#endif
+#    ifndef OPENTELEMETRY_OPTION_USE_STD_SPAN
+#      define OPENTELEMETRY_OPTION_USE_STD_SPAN 1
+#    endif
+#    if OPENTELEMETRY_OPTION_USE_STD_SPAN
+#      include "opentelemetry/std/span.h"
+#    endif
+#  endif /* OPENTELEMETRY_STL_VERSION >= 2020 */
+#endif   /* OPENTELEMETRY_STL_VERSION */
 
 // Fallback to `nostd::span` if necessary
-#if !defined(HAVE_SPAN)
+#if !defined(OPENTELEMETRY_HAVE_SPAN)
 #  include <array>
 #  include <cassert>
 #  include <cstddef>

api/include/opentelemetry/nostd/string_view.h

@@ -3,9 +3,14 @@
 
 #pragma once
 
-#ifdef HAVE_CPP_STDLIB
-#  include "opentelemetry/std/string_view.h"
-#else
+#if defined(OPENTELEMETRY_STL_VERSION)
+#  if OPENTELEMETRY_STL_VERSION >= 2017
+#    include "opentelemetry/std/string_view.h"
+#    define OPENTELEMETRY_HAVE_STD_STRING_VIEW
+#  endif
+#endif
+
+#if !defined(OPENTELEMETRY_HAVE_STD_STRING_VIEW)
 #  include <algorithm>
 #  include <cstddef>
 #  include <cstring>
@@ -216,4 +221,4 @@ struct hash<OPENTELEMETRY_NAMESPACE::nostd::string_view>
   }
 };
 }  // namespace std
-#endif
+#endif /* OPENTELEMETRY_HAVE_STD_STRING_VIEW */

api/include/opentelemetry/nostd/type_traits.h

@@ -3,9 +3,14 @@
 
 #pragma once
 
-#ifdef HAVE_CPP_STDLIB
-#  include "opentelemetry/std/type_traits.h"
-#else
+#if defined(OPENTELEMETRY_STL_VERSION)
+#  if OPENTELEMETRY_STL_VERSION >= 2011
+#    include "opentelemetry/std/type_traits.h"
+#    define OPENTELEMETRY_HAVE_STD_TYPE_TRAITS
+#  endif
+#endif
+
+#if !defined(OPENTELEMETRY_HAVE_STD_TYPE_TRAITS)
 #  include <array>
 #  include <type_traits>
 
@@ -154,4 +159,4 @@ struct is_trivially_move_assignable
 #  endif
 }  // namespace nostd
 OPENTELEMETRY_END_NAMESPACE
-#endif
+#endif /* OPENTELEMETRY_HAVE_STD_TYPE_TRAITS */

api/include/opentelemetry/nostd/unique_ptr.h

@@ -3,9 +3,14 @@
 
 #pragma once
 
-#ifdef HAVE_CPP_STDLIB
-#  include "opentelemetry/std/unique_ptr.h"
-#else
+#if defined(OPENTELEMETRY_STL_VERSION)
+#  if OPENTELEMETRY_STL_VERSION >= 2011
+#    include "opentelemetry/std/unique_ptr.h"
+#    define OPENTELEMETRY_HAVE_STD_UNIQUE_PTR
+#  endif
+#endif
+
+#if !defined(OPENTELEMETRY_HAVE_STD_UNIQUE_PTR)
 #  include <cstddef>
 #  include <memory>
 #  include <type_traits>
@@ -172,4 +177,4 @@ bool operator!=(std::nullptr_t, const unique_ptr<T> &rhs) noexcept
 }
 }  // namespace nostd
 OPENTELEMETRY_END_NAMESPACE
-#endif
+#endif /* OPENTELEMETRY_HAVE_STD_UNIQUE_PTR */

api/include/opentelemetry/nostd/utility.h

@@ -3,10 +3,14 @@
 
 #pragma once
 
-#ifdef HAVE_CPP_STDLIB
-#  include "opentelemetry/std/utility.h"
-#else
+#if defined(OPENTELEMETRY_STL_VERSION)
+#  if OPENTELEMETRY_STL_VERSION >= 2014
+#    include "opentelemetry/std/utility.h"
+#    define OPENTELEMETRY_HAVE_STD_UTILITY
+#  endif
+#endif
 
+#if !defined(OPENTELEMETRY_HAVE_STD_UTILITY)
 #  include <cstddef>
 #  include <initializer_list>
 #  include <type_traits>
@@ -153,4 +157,4 @@ struct in_place_type_t
 };
 }  // namespace nostd
 OPENTELEMETRY_END_NAMESPACE
-#endif
+#endif /* OPENTELEMETRY_HAVE_STD_UTILITY */

api/include/opentelemetry/nostd/variant.h

@@ -5,9 +5,14 @@
 
 #include "opentelemetry/version.h"
 
-#ifdef HAVE_CPP_STDLIB
-#  include "opentelemetry/std/variant.h"
-#else
+#if defined(OPENTELEMETRY_STL_VERSION)
+#  if OPENTELEMETRY_STL_VERSION >= 2017
+#    include "opentelemetry/std/variant.h"
+#    define OPENTELEMETRY_HAVE_STD_VARIANT
+#  endif
+#endif
+
+#if !defined(OPENTELEMETRY_HAVE_STD_VARIANT)
 
 #  ifndef HAVE_ABSEIL
 // We use a LOCAL snapshot of Abseil that is known to compile with Visual Studio 2015.
@@ -73,4 +78,4 @@ using absl::visit;
 }  // namespace nostd
 OPENTELEMETRY_END_NAMESPACE
 
-#endif
+#endif /* OPENTELEMETRY_HAVE_STD_VARIANT */

api/include/opentelemetry/std/span.h

@@ -12,26 +12,26 @@
 #  if __has_include(<version>)  // Check for __cpp_{feature}
 #    include <version>
 #    if defined(__cpp_lib_span) && __cplusplus > 201703L
-#      define HAVE_SPAN
+#      define OPENTELEMETRY_HAVE_SPAN
 #    endif
 #  endif
-#  if !defined(HAVE_SPAN)
+#  if !defined(OPENTELEMETRY_HAVE_SPAN)
 #    // Check for Visual Studio span
 #    if defined(_MSVC_LANG) && _HAS_CXX20
-#      define HAVE_SPAN
+#      define OPENTELEMETRY_HAVE_SPAN
 #    endif
 #    // Check for other compiler span implementation
 #    if !defined(_MSVC_LANG) && __has_include(<span>) && __cplusplus > 201703L
 // This works as long as compiler standard is set to C++20
-#      define HAVE_SPAN
+#      define OPENTELEMETRY_HAVE_SPAN
 #    endif
 #  endif
 #  if !__has_include(<gsl/gsl>)
 #    undef HAVE_GSL
 #  endif
 #endif
 
-#if !defined(HAVE_SPAN)
+#if !defined(OPENTELEMETRY_HAVE_SPAN)
 #  if defined(HAVE_GSL)
 #    include <type_traits>
 // Guidelines Support Library provides an implementation of std::span
@@ -44,12 +44,12 @@ template <class ElementType, std::size_t Extent = gsl::dynamic_extent>
 using span = gsl::span<ElementType, Extent>;
 }  // namespace nostd
 OPENTELEMETRY_END_NAMESPACE
-#    define HAVE_SPAN
+#    define OPENTELEMETRY_HAVE_SPAN
 #  else
 // No `gsl::span`, no `std::span`, fallback to `nostd::span`
 #  endif
 
-#else  // HAVE_SPAN
+#else  // OPENTELEMETRY_HAVE_SPAN
 // Using std::span (https://wg21.link/P0122R7) from Standard Library available in C++20 :
 // - GCC libstdc++ 10+
 // - Clang libc++ 7
@@ -66,4 +66,4 @@ template <class ElementType, std::size_t Extent = nostd::dynamic_extent>
 using span = std::span<ElementType, Extent>;
 }  // namespace nostd
 OPENTELEMETRY_END_NAMESPACE
-#endif  // of HAVE_SPAN
+#endif  // if OPENTELEMETRY_HAVE_SPAN