[libc++] Implements the new version header generator. (llvm#97847)

The generator makes a few changes to the output
- removes the synopsis, it did not really show what was implemented
correctly.
- the output now is clang-format clean.

This code uses the new FTM data structure. Since the contents of this
structure are not up-to-date the code is only used in its tests.

libcxx/test/libcxx/feature_test_macro/ftm_metadata.sh.py

@@ -0,0 +1,51 @@
+# ===----------------------------------------------------------------------===##
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+# ===----------------------------------------------------------------------===##
+
+# RUN: %{python} %s %{libcxx-dir}/utils %{libcxx-dir}/test/libcxx/feature_test_macro/test_data.json
+
+import sys
+
+sys.path.append(sys.argv[1])
+from generate_feature_test_macro_components import FeatureTestMacros
+
+
+def test(output, expected):
+    assert output == expected, f"expected\n{expected}\n\noutput\n{output}"
+
+
+ftm = FeatureTestMacros(sys.argv[2])
+test(
+    ftm.ftm_metadata,
+    {
+        "__cpp_lib_any": {
+            "headers": ["any"],
+            "test_suite_guard": None,
+            "libcxx_guard": None,
+        },
+        "__cpp_lib_barrier": {
+            "headers": ["barrier"],
+            "test_suite_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && (!defined(_LIBCPP_VERSION) || _LIBCPP_AVAILABILITY_HAS_SYNC)",
+            "libcxx_guard": "!defined(_LIBCPP_HAS_NO_THREADS) && _LIBCPP_AVAILABILITY_HAS_SYNC",
+        },
+        "__cpp_lib_format": {
+            "headers": ["format"],
+            "test_suite_guard": None,
+            "libcxx_guard": None,
+        },
+        "__cpp_lib_parallel_algorithm": {
+            "headers": ["algorithm", "numeric"],
+            "test_suite_guard": None,
+            "libcxx_guard": None,
+        },
+        "__cpp_lib_variant": {
+            "headers": ["variant"],
+            "test_suite_guard": None,
+            "libcxx_guard": None,
+        },
+    },
+)

libcxx/test/libcxx/feature_test_macro/implemented_ftms.sh.py

@@ -31,7 +31,7 @@ def test(output, expected):
         "__cpp_lib_barrier": {
             "c++20": "201907L",
             "c++23": "201907L",
-            "c++26": "201907L",
+            "c++26": "299900L",
         },
         "__cpp_lib_format": {
             "c++20": None,

libcxx/test/libcxx/feature_test_macro/standard_ftms.sh.py

@@ -31,7 +31,7 @@ def test(output, expected):
         "__cpp_lib_barrier": {
             "c++20": "201907L",
             "c++23": "201907L",
-            "c++26": "201907L",
+            "c++26": "299900L",
         },
         "__cpp_lib_format": {
             "c++20": "202110L",

libcxx/test/libcxx/feature_test_macro/test_data.json

@@ -23,6 +23,13 @@
             "implemented": true
           }
         ]
+      },
+      "c++26": {
+        "299900": [
+          {
+            "implemented": true
+          }
+        ]
       }
     },
     "headers": [

libcxx/test/libcxx/feature_test_macro/version_header.sh.py

@@ -0,0 +1,73 @@
+# ===----------------------------------------------------------------------===##
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+# ===----------------------------------------------------------------------===##
+
+# RUN: %{python} %s %{libcxx-dir}/utils %{libcxx-dir}/test/libcxx/feature_test_macro/test_data.json
+
+import sys
+
+sys.path.append(sys.argv[1])
+from generate_feature_test_macro_components import FeatureTestMacros
+
+
+def test(output, expected):
+    assert output == expected, f"expected\n{expected}\n\noutput\n{output}"
+
+
+ftm = FeatureTestMacros(sys.argv[2])
+test(
+    ftm.version_header,
+    """// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_VERSION
+#define _LIBCPP_VERSION
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER >= 17
+#  define __cpp_lib_any 201606L
+#  define __cpp_lib_parallel_algorithm 201603L
+#  define __cpp_lib_variant 202102L
+#endif // _LIBCPP_STD_VER >= 17
+
+#if _LIBCPP_STD_VER >= 20
+#  if !defined(_LIBCPP_HAS_NO_THREADS) && _LIBCPP_AVAILABILITY_HAS_SYNC
+#    define __cpp_lib_barrier 201907L
+#  endif
+// define __cpp_lib_format 202110L
+#  undef __cpp_lib_variant
+#  define __cpp_lib_variant 202106L
+#endif // _LIBCPP_STD_VER >= 20
+
+#if _LIBCPP_STD_VER >= 23
+// define __cpp_lib_format 202207L
+#endif // _LIBCPP_STD_VER >= 23
+
+#if _LIBCPP_STD_VER >= 26
+#  if !defined(_LIBCPP_HAS_NO_THREADS) && _LIBCPP_AVAILABILITY_HAS_SYNC
+#    undef __cpp_lib_barrier
+#    define __cpp_lib_barrier 299900L
+#  endif
+// define __cpp_lib_format 202311L
+#  undef __cpp_lib_variant
+#  define __cpp_lib_variant 202306L
+#endif // _LIBCPP_STD_VER >= 26
+
+#endif // _LIBCPP_VERSION
+""",
+)

libcxx/test/libcxx/feature_test_macro/version_header_implementation.sh.py

@@ -0,0 +1,114 @@
+# ===----------------------------------------------------------------------===##
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+# ===----------------------------------------------------------------------===##
+
+# RUN: %{python} %s %{libcxx-dir}/utils %{libcxx-dir}/test/libcxx/feature_test_macro/test_data.json
+
+import sys
+
+sys.path.append(sys.argv[1])
+from generate_feature_test_macro_components import FeatureTestMacros
+
+
+def test(output, expected):
+    assert output == expected, f"expected\n{expected}\n\noutput\n{output}"
+
+
+ftm = FeatureTestMacros(sys.argv[2])
+test(
+    ftm.version_header_implementation,
+    {
+        "17": [
+            {
+                "__cpp_lib_any": {
+                    "value": "201606L",
+                    "implemented": True,
+                    "need_undef": False,
+                    "condition": None,
+                },
+            },
+            {
+                "__cpp_lib_parallel_algorithm": {
+                    "value": "201603L",
+                    "implemented": True,
+                    "need_undef": False,
+                    "condition": None,
+                },
+            },
+            {
+                "__cpp_lib_variant": {
+                    "value": "202102L",
+                    "implemented": True,
+                    "need_undef": False,
+                    "condition": None,
+                },
+            },
+        ],
+        "20": [
+            {
+                "__cpp_lib_barrier": {
+                    "value": "201907L",
+                    "implemented": True,
+                    "need_undef": False,
+                    "condition": "!defined(_LIBCPP_HAS_NO_THREADS) && _LIBCPP_AVAILABILITY_HAS_SYNC",
+                },
+            },
+            {
+                "__cpp_lib_format": {
+                    "value": "202110L",
+                    "implemented": False,
+                    "need_undef": False,
+                    "condition": None,
+                },
+            },
+            {
+                "__cpp_lib_variant": {
+                    "value": "202106L",
+                    "implemented": True,
+                    "need_undef": True,
+                    "condition": None,
+                },
+            },
+        ],
+        "23": [
+            {
+                "__cpp_lib_format": {
+                    "value": "202207L",
+                    "implemented": False,
+                    "need_undef": False,
+                    "condition": None,
+                },
+            },
+        ],
+        "26": [
+            {
+                "__cpp_lib_barrier": {
+                    "value": "299900L",
+                    "implemented": True,
+                    "need_undef": True,
+                    "condition": "!defined(_LIBCPP_HAS_NO_THREADS) && _LIBCPP_AVAILABILITY_HAS_SYNC",
+                },
+            },
+            {
+                "__cpp_lib_format": {
+                    "value": "202311L",
+                    "implemented": False,
+                    "need_undef": False,
+                    "condition": None,
+                },
+            },
+            {
+                "__cpp_lib_variant": {
+                    "value": "202306L",
+                    "implemented": True,
+                    "need_undef": True,
+                    "condition": None,
+                },
+            },
+        ],
+    },
+)