PyTorch -> C++17 (pytorch#98209) (pytorch#100557)

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### <samp>🤖 Generated by Copilot at 4f0b524</samp>

This pull request updates the codebase and the documentation to use C++17 instead of C++14 as the minimum required C++ standard. This affects the `ATen`, `c10`, and `torch` libraries and their dependencies, as well as the CI system and the `conda` package metadata.

Pull Request resolved: pytorch#100557
Approved by: https://github.com/malfet

Author: r-barnes

aten/conda/meta.yaml

@@ -26,7 +26,7 @@ requirements:
 about:
   home: https://github.com/pytorch/pytorch
   license: BSD
-  summary: A TENsor library for C++14
+  summary: A TENsor library for C++17
 
 extra:
   recipe-maintainers:

aten/src/ATen/ATen.h

@@ -1,7 +1,7 @@
 #pragma once
 
-#if !defined(_MSC_VER) && __cplusplus < 201402L
-#error C++14 or later compatible compiler is required to use ATen.
+#if !defined(_MSC_VER) && __cplusplus < 201703L
+#error C++17 or later compatible compiler is required to use ATen.
 #endif
 
 #include <ATen/Context.h>

aten/src/ATen/cpu/tbb/CMakeLists.txt

@@ -121,9 +121,9 @@ endif()
 if(UNIX)
   add_definitions(-DUSE_PTHREAD)
 
-   check_cxx_compiler_flag("-std=c++14" SUPPORTS_STDCXX14)
-  if(SUPPORTS_STDCXX14)
-    set(CMAKE_CXX_FLAGS "-std=c++14 ${CMAKE_CXX_FLAGS}")
+   check_cxx_compiler_flag("-std=c++17" SUPPORTS_STDCXX17)
+  if(SUPPORTS_STDCXX17)
+    set(CMAKE_CXX_FLAGS "-std=c++17 ${CMAKE_CXX_FLAGS}")
   endif()
 
    check_cxx_compiler_flag("-mrtm -Werror" SUPPORTS_MRTM)

aten/src/ATen/test/test_install/CMakeLists.txt

@@ -2,9 +2,9 @@ cmake_minimum_required(VERSION 3.0)
 find_package(ATen REQUIRED)
 include_directories(${ATEN_INCLUDE_DIR})
 
-# C++14
+# C++17
 if(not MSVC)
-    set(CMAKE_CXX_FLAGS "--std=c++14 ${CMAKE_CXX_FLAGS}")
+    set(CMAKE_CXX_FLAGS "--std=c++17 ${CMAKE_CXX_FLAGS}")
 endif()
 add_executable(main main.cpp)
 target_link_libraries(main ${ATEN_LIBRARIES})

c10/util/C++17.h

@@ -22,9 +22,9 @@
     "You're trying to build PyTorch with a too old version of Clang. We need Clang 4 or later."
 #endif
 
-#if (defined(_MSC_VER) && (!defined(_MSVC_LANG) || _MSVC_LANG < 201402L)) || \
-    (!defined(_MSC_VER) && __cplusplus < 201402L)
-#error You need C++14 to compile PyTorch
+#if (defined(_MSC_VER) && (!defined(_MSVC_LANG) || _MSVC_LANG < 201703L)) || \
+    (!defined(_MSC_VER) && __cplusplus < 201703L)
+#error You need C++17 to compile PyTorch
 #endif
 
 #if defined(_WIN32) && (defined(min) || defined(max))

caffe2/contrib/aten/README.md

@@ -1,7 +1,7 @@
 # An ATen operator for Caffe2
 
 ATen is a simple tensor library thats exposes the Tensor operations in Torch
-and PyTorch directly in C++14. This library provides a generated wrapper around the ATen API
+and PyTorch directly in C++17. This library provides a generated wrapper around the ATen API
 that makes these functions available in Caffe2 as an operator. It also makes it accessible using the
 ToffeeIR.
 

torch/csrc/api/include/torch/all.h

@@ -1,7 +1,7 @@
 #pragma once
 
-#if !defined(_MSC_VER) && __cplusplus < 201402L
-#error C++14 or later compatible compiler is required to use PyTorch.
+#if !defined(_MSC_VER) && __cplusplus < 201703L
+#error C++17 or later compatible compiler is required to use PyTorch.
 #endif
 
 #include <torch/autograd.h>