Require C++17 for compiling Thrust and CUB (#3255)

* Issue an unsuppressable warning when compiling with < C++17
* Remove C++11/14 presets
* Remove CCCL_IGNORE_DEPRECATED_CPP_DIALECT from headers
* Remove [CUB|THRUST|TCT]_IGNORE_DEPRECATED_CPP_[11|14]
* Remove CUB_ENABLE_DIALECT_CPP[11|14]
* Update CI runs
* Remove C++11/14 CI runs for CUB and Thrust
* Raise compiler minimum versions for C++17
* Update ReadMe
* Drop Thrust's cpp14_required.h
* Add escape hatch for C++17 removal

Fixes: #3252

Author: bernhardmgruber

CMakePresets.json

@@ -69,8 +69,6 @@
         "CUB_ENABLE_TESTING": true,
         "CUB_ENABLE_EXAMPLES": true,
         "CUB_SEPARATE_CATCH2": true,
-        "CUB_ENABLE_DIALECT_CPP11": true,
-        "CUB_ENABLE_DIALECT_CPP14": true,
         "CUB_ENABLE_DIALECT_CPP17": true,
         "CUB_ENABLE_DIALECT_CPP20": true,
         "THRUST_ENABLE_MULTICONFIG": true,
@@ -232,30 +230,10 @@
         "CUB_ENABLE_TESTING": true,
         "CUB_ENABLE_EXAMPLES": true,
         "CUB_SEPARATE_CATCH2": true,
-        "CUB_ENABLE_DIALECT_CPP11": false,
-        "CUB_ENABLE_DIALECT_CPP14": false,
         "CUB_ENABLE_DIALECT_CPP17": false,
         "CUB_ENABLE_DIALECT_CPP20": false
       }
     },
-    {
-      "name": "cub-cpp11",
-      "displayName": "CUB: C++11",
-      "inherits": "cub-base",
-      "cacheVariables": {
-        "CCCL_IGNORE_DEPRECATED_CPP_DIALECT": true,
-        "CUB_ENABLE_DIALECT_CPP11": true
-      }
-    },
-    {
-      "name": "cub-cpp14",
-      "displayName": "CUB: C++14",
-      "inherits": "cub-base",
-      "cacheVariables": {
-        "CCCL_IGNORE_DEPRECATED_CPP_DIALECT": true,
-        "CUB_ENABLE_DIALECT_CPP14": true
-      }
-    },
     {
       "name": "cub-cpp17",
       "displayName": "CUB: C++17",
@@ -289,24 +267,6 @@
         "THRUST_MULTICONFIG_ENABLE_DIALECT_CPP20": false
       }
     },
-    {
-      "name": "thrust-cpp11",
-      "displayName": "Thrust: C++11",
-      "inherits": "thrust-base",
-      "cacheVariables": {
-        "CCCL_IGNORE_DEPRECATED_CPP_DIALECT": true,
-        "THRUST_MULTICONFIG_ENABLE_DIALECT_CPP11": true
-      }
-    },
-    {
-      "name": "thrust-cpp14",
-      "displayName": "Thrust: C++14",
-      "inherits": "thrust-base",
-      "cacheVariables": {
-        "CCCL_IGNORE_DEPRECATED_CPP_DIALECT": true,
-        "THRUST_MULTICONFIG_ENABLE_DIALECT_CPP14": true
-      }
-    },
     {
       "name": "thrust-cpp17",
       "displayName": "Thrust: C++17",
@@ -520,14 +480,6 @@
         "libcudacxx-base"
       ]
     },
-    {
-      "name": "cub-cpp11",
-      "configurePreset": "cub-cpp11"
-    },
-    {
-      "name": "cub-cpp14",
-      "configurePreset": "cub-cpp14"
-    },
     {
       "name": "cub-cpp17",
       "configurePreset": "cub-cpp17"
@@ -536,14 +488,6 @@
       "name": "cub-cpp20",
       "configurePreset": "cub-cpp20"
     },
-    {
-      "name": "thrust-cpp11",
-      "configurePreset": "thrust-cpp11"
-    },
-    {
-      "name": "thrust-cpp14",
-      "configurePreset": "thrust-cpp14"
-    },
     {
       "name": "thrust-cpp17",
       "configurePreset": "thrust-cpp17"
@@ -736,16 +680,6 @@
         }
       }
     },
-    {
-      "name": "cub-nolid-cpp11",
-      "configurePreset": "cub-cpp11",
-      "inherits": "cub-nolid-base"
-    },
-    {
-      "name": "cub-nolid-cpp14",
-      "configurePreset": "cub-cpp14",
-      "inherits": "cub-nolid-base"
-    },
     {
       "name": "cub-nolid-cpp17",
       "configurePreset": "cub-cpp17",
@@ -756,16 +690,6 @@
       "configurePreset": "cub-cpp20",
       "inherits": "cub-nolid-base"
     },
-    {
-      "name": "cub-lid0-cpp11",
-      "configurePreset": "cub-cpp11",
-      "inherits": "cub-lid0-base"
-    },
-    {
-      "name": "cub-lid0-cpp14",
-      "configurePreset": "cub-cpp14",
-      "inherits": "cub-lid0-base"
-    },
     {
       "name": "cub-lid0-cpp17",
       "configurePreset": "cub-cpp17",
@@ -776,16 +700,6 @@
       "configurePreset": "cub-cpp20",
       "inherits": "cub-lid0-base"
     },
-    {
-      "name": "cub-lid1-cpp11",
-      "configurePreset": "cub-cpp11",
-      "inherits": "cub-lid1-base"
-    },
-    {
-      "name": "cub-lid1-cpp14",
-      "configurePreset": "cub-cpp14",
-      "inherits": "cub-lid1-base"
-    },
     {
       "name": "cub-lid1-cpp17",
       "configurePreset": "cub-cpp17",
@@ -796,16 +710,6 @@
       "configurePreset": "cub-cpp20",
       "inherits": "cub-lid1-base"
     },
-    {
-      "name": "cub-lid2-cpp11",
-      "configurePreset": "cub-cpp11",
-      "inherits": "cub-lid2-base"
-    },
-    {
-      "name": "cub-lid2-cpp14",
-      "configurePreset": "cub-cpp14",
-      "inherits": "cub-lid2-base"
-    },
     {
       "name": "cub-lid2-cpp17",
       "configurePreset": "cub-cpp17",
@@ -816,16 +720,6 @@
       "configurePreset": "cub-cpp20",
       "inherits": "cub-lid2-base"
     },
-    {
-      "name": "cub-cpp11",
-      "configurePreset": "cub-cpp11",
-      "inherits": "cub-base"
-    },
-    {
-      "name": "cub-cpp14",
-      "configurePreset": "cub-cpp14",
-      "inherits": "cub-base"
-    },
     {
       "name": "cub-cpp17",
       "configurePreset": "cub-cpp17",
@@ -866,16 +760,6 @@
         }
       }
     },
-    {
-      "name": "thrust-gpu-cpp11",
-      "configurePreset": "thrust-cpp11",
-      "inherits": "thrust-gpu-base"
-    },
-    {
-      "name": "thrust-gpu-cpp14",
-      "configurePreset": "thrust-cpp14",
-      "inherits": "thrust-gpu-base"
-    },
     {
       "name": "thrust-gpu-cpp17",
       "configurePreset": "thrust-cpp17",
@@ -886,16 +770,6 @@
       "configurePreset": "thrust-cpp20",
       "inherits": "thrust-gpu-base"
     },
-    {
-      "name": "thrust-cpu-cpp11",
-      "configurePreset": "thrust-cpp11",
-      "inherits": "thrust-cpu-base"
-    },
-    {
-      "name": "thrust-cpu-cpp14",
-      "configurePreset": "thrust-cpp14",
-      "inherits": "thrust-cpu-base"
-    },
     {
       "name": "thrust-cpu-cpp17",
       "configurePreset": "thrust-cpp17",
@@ -906,16 +780,6 @@
       "configurePreset": "thrust-cpp20",
       "inherits": "thrust-cpu-base"
     },
-    {
-      "name": "thrust-cpp11",
-      "configurePreset": "thrust-cpp11",
-      "inherits": "thrust-base"
-    },
-    {
-      "name": "thrust-cpp14",
-      "configurePreset": "thrust-cpp14",
-      "inherits": "thrust-base"
-    },
     {
       "name": "thrust-cpp17",
       "configurePreset": "thrust-cpp17",

README.md

@@ -269,8 +269,8 @@ But we will not invest significant time in triaging or fixing issues for older c
 In the spirit of "You only support what you test", see our [CI Overview](https://github.com/NVIDIA/cccl/blob/main/ci-overview.md) for more information on exactly what we test.
 
 ### C++ Dialects
-- C++11 (Deprecated in Thrust/CUB, to be removed in next major version)
-- C++14 (Deprecated in Thrust/CUB, to be removed in next major version)
+- C++11 (only libcu++)
+- C++14 (only libcu++)
 - C++17
 - C++20
 

ci/matrix.yaml

@@ -13,7 +13,8 @@ workflows:
     # Old CTK/compiler
     - {jobs: ['build'], std: 'minmax', ctk: '12.0', cxx: ['gcc7', 'gcc9', 'clang9', 'msvc2019']}
     # Current CTK build-only
-    - {jobs: ['build'], std: [11, 14], cxx: ['gcc7', 'clang9']}
+    - {jobs: ['build'], std: [11, 14], cxx: ['gcc7', 'clang9'], project: 'libcudacxx'}
+    - {jobs: ['build'], std: [17], cxx: ['gcc7', 'clang9']}
     - {jobs: ['build'], std: 'max', cxx: ['gcc8', 'gcc9', 'gcc10', 'gcc11', 'gcc12']}
     - {jobs: ['build'], std: 'max', cxx: ['clang10', 'clang11', 'clang12', 'clang13', 'clang14', 'clang15', 'clang16', 'clang17']}
     - {jobs: ['build'], std: 'max', cxx: ['msvc2019']}
@@ -246,11 +247,11 @@ projects:
     stds: [11, 14, 17, 20]
   cub:
     name: 'CUB'
-    stds: [11, 14, 17, 20]
+    stds: [17, 20]
     job_map: { test: ['test_nolid', 'test_lid0', 'test_lid1', 'test_lid2'] }
   thrust:
     name: 'Thrust'
-    stds: [11, 14, 17, 20]
+    stds: [17, 20]
     job_map: { test: ['test_cpu', 'test_gpu'] }
   cudax:
     stds: [17, 20]

cub/cmake/CubBuildTargetList.cmake

@@ -150,16 +150,6 @@ function(cub_build_target_list)
     cmake_minimum_required(VERSION 3.18.3)
   endif()
 
-  # Supported versions of MSVC do not distinguish between C++11 and C++14.
-  # Warn the user that they may be generating a ton of redundant targets.
-  if ("MSVC" STREQUAL "${CMAKE_CXX_COMPILER_ID}" AND
-      CUB_ENABLE_DIALECT_CPP11)
-    message(WARNING
-      "Supported versions of MSVC (2017+) do not distinguish between C++11 "
-      "and C++14. The requested C++11 targets will be built with C++14."
-    )
-  endif()
-
   # Generic config flags:
   macro(add_flag_option flag docstring default)
     set(opt "CCCL_${flag}")

cub/cub/util_cpp_dialect.cuh

@@ -44,17 +44,9 @@
 
 // Deprecation warnings may be silenced by defining the following macros. These
 // may be combined.
-// - CCCL_IGNORE_DEPRECATED_CPP_DIALECT:
-//   Ignore all deprecated C++ dialects and outdated compilers.
-// - CCCL_IGNORE_DEPRECATED_CPP_11:
-//   Ignore deprecation warnings when compiling with C++11. C++03 and outdated
-//   compilers will still issue warnings.
-// - CCCL_IGNORE_DEPRECATED_CPP_14:
-//   Ignore deprecation warnings when compiling with C++14. C++03 and outdated
-//   compilers will still issue warnings.
 // - CCCL_IGNORE_DEPRECATED_COMPILER
 //   Ignore deprecation warnings when using deprecated compilers. Compiling
-//   with C++03, C++11 and C++14 will still issue warnings.
+//   with deprecated C++ dialects will still issue warnings.
 
 #  define CUB_CPP_DIALECT _CCCL_STD_VER
 
@@ -65,19 +57,18 @@
 #    define CUB_COMP_DEPR_IMPL(msg) _CCCL_PRAGMA(GCC warning #msg)
 #  endif
 
+// Compiler checks:
 // clang-format off
 #  define CUB_COMPILER_DEPRECATION(REQ) \
     CUB_COMP_DEPR_IMPL(CUB requires at least REQ. Define CCCL_IGNORE_DEPRECATED_COMPILER to suppress this message.)
 
 #  define CUB_COMPILER_DEPRECATION_SOFT(REQ, CUR)                                                        \
     CUB_COMP_DEPR_IMPL(                                                                                  \
       CUB requires at least REQ. CUR is deprecated but still supported. CUR support will be removed in a \
-        future release. Define CCCL_IGNORE_DEPRECATED_CPP_DIALECT to suppress this message.)
+        future release. Define CCCL_IGNORE_DEPRECATED_COMPILER to suppress this message.)
 // clang-format on
 
 #  ifndef CCCL_IGNORE_DEPRECATED_COMPILER
-
-// Compiler checks:
 #    if _CCCL_COMPILER(GCC, <, 7)
 CUB_COMPILER_DEPRECATION(GCC 7.0);
 #    elif _CCCL_COMPILER(CLANG, <, 7)
@@ -89,24 +80,18 @@ CUB_COMPILER_DEPRECATION(MSVC 2019(19.20 / 16.0 / 14.20));
 // >=2017, <2019. Soft deprecation message:
 CUB_COMPILER_DEPRECATION_SOFT(MSVC 2019(19.20 / 16.0 / 14.20), MSVC 2017);
 #    endif
-
 #  endif // CCCL_IGNORE_DEPRECATED_COMPILER
 
-#  if _CCCL_STD_VER < 2011
-// <C++11. Hard upgrade message:
-CUB_COMPILER_DEPRECATION(C++ 17);
-#  elif _CCCL_STD_VER == 2011 && !defined(CCCL_IGNORE_DEPRECATED_CPP_11)
-// =C++11. Soft upgrade message:
-CUB_COMPILER_DEPRECATION_SOFT(C++ 17, C++ 11);
-#  elif _CCCL_STD_VER == 2014 && !defined(CCCL_IGNORE_DEPRECATED_CPP_14)
-// =C++14. Soft upgrade message:
-CUB_COMPILER_DEPRECATION_SOFT(C++ 17, C++ 14);
-#  endif // _CCCL_STD_VER >= 2017
-
 #  undef CUB_COMPILER_DEPRECATION_SOFT
 #  undef CUB_COMPILER_DEPRECATION
+
+// C++17 dialect check:
+#  ifndef CCCL_IGNORE_DEPRECATED_CPP_DIALECT
+#    if _CCCL_STD_VER < 2017
+CUB_COMP_DEPR_IMPL(CUB requires at least C++ 17. Define CCCL_IGNORE_DEPRECATED_CPP_DIALECT to suppress this message.)
+#    endif // _CCCL_STD_VER >= 2017
+#  endif
+
 #  undef CUB_COMP_DEPR_IMPL
-#  undef CUB_COMP_DEPR_IMPL0
-#  undef CUB_COMP_DEPR_IMPL1
 
 #endif // !_CCCL_DOXYGEN_INVOKED

lib/cmake/thrust/thrust-config.cmake

@@ -237,36 +237,10 @@ function(thrust_create_target target_name)
     target_compile_definitions(${target_name} INTERFACE "THRUST_FORCE_64_BIT_OFFSET_TYPE")
   endif()
 
-  # This would be nice to enforce, but breaks when using old cmake + new
-  # compiler, since cmake doesn't know what features the new compiler version
-  # supports.
-  # Leaving this here as a reminder not to add it back. Just let the
-  # compile-time checks in thrust/detail/config/cpp_dialect.h handle it.
-  #
-  #  if (NOT TCT_IGNORE_DEPRECATED_CPP_DIALECT)
-  #    if (TCT_IGNORE_DEPRECATED_CPP_11)
-  #      target_compile_features(${target_name} INTERFACE cxx_std_11)
-  #    else()
-  #      target_compile_features(${target_name} INTERFACE cxx_std_14)
-  #    endif()
-  #  endif()
-
-  if (TCT_IGNORE_DEPRECATED_CPP_DIALECT OR CCCL_IGNORE_DEPRECATED_CPP_DIALECT)
-    target_compile_definitions(${target_name} INTERFACE "CCCL_IGNORE_DEPRECATED_CPP_DIALECT")
-  endif()
-
   if (TCT_IGNORE_DEPRECATED_API OR CCCL_IGNORE_DEPRECATED_API)
     target_compile_definitions(${target_name} INTERFACE "CCCL_IGNORE_DEPRECATED_API")
   endif()
 
-  if (TCT_IGNORE_DEPRECATED_CPP_11 OR CCCL_IGNORE_DEPRECATED_CPP_11)
-    target_compile_definitions(${target_name} INTERFACE "CCCL_IGNORE_DEPRECATED_CPP_11")
-  endif()
-
-  if (TCT_IGNORE_DEPRECATED_CPP_14 OR CCCL_IGNORE_DEPRECATED_CPP_14)
-    target_compile_definitions(${target_name} INTERFACE "CCCL_IGNORE_DEPRECATED_CPP_14")
-  endif()
-
   if (TCT_IGNORE_DEPRECATED_COMPILER OR CCCL_IGNORE_DEPRECATED_COMPILER)
     target_compile_definitions(${target_name} INTERFACE "CCCL_IGNORE_DEPRECATED_COMPILER")
   endif()