[libcxx-commits] [libcxx] [libcxx] Define _LIBCPP_HAS_C8RTOMB_MBRTOC8 for picolibc (PR #158648)

[Victor Campos via libcxx-commits]

https://github.com/vhscampos updated https://github.com/llvm/llvm-project/pull/158648

>From 02c37c15a06ab8b1a064f22acff18eed510383c0 Mon Sep 17 00:00:00 2001
From: Victor Campos <victor.campos at arm.com>
Date: Thu, 7 Aug 2025 16:03:44 +0100
Subject: [PATCH] [libcxx] Define _LIBCPP_HAS_C8RTOMB_MBRTOC8 for picolibc

Starting from picolibc 1.8.9, the `char8_t` related functions are
provided.

This patch adds logic to detect the underlying picolibc version and
define the `_LIBCPP_HAS_C8RTOMB_MBRTOC8 macro` accordingly.
---
 libcxx/include/__config                       |  4 ++-
 .../depr.c.headers/uchar_h.compile.pass.cpp   |  5 ----
 .../uchar_h_char8_t.compile.pass.cpp          | 27 +++++++++++++++++
 .../strings/c.strings/cuchar.compile.pass.cpp |  5 ----
 .../c.strings/cuchar_char8_t.compile.pass.cpp | 27 +++++++++++++++++
 .../c.strings/no_c8rtomb_mbrtoc8.verify.cpp   | 30 -------------------
 6 files changed, 57 insertions(+), 41 deletions(-)
 create mode 100644 libcxx/test/std/depr/depr.c.headers/uchar_h_char8_t.compile.pass.cpp
 create mode 100644 libcxx/test/std/strings/c.strings/cuchar_char8_t.compile.pass.cpp
 delete mode 100644 libcxx/test/std/strings/c.strings/no_c8rtomb_mbrtoc8.verify.cpp

diff --git a/libcxx/include/__config b/libcxx/include/__config
index b4c081dcdff1b..5971a3c5407b9 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -1021,7 +1021,9 @@ typedef __char32_t char32_t;
 // the latter depends on internal GNU libc details that are not appropriate
 // to depend on here, so any declarations present when __cpp_char8_t is not
 // defined are ignored.
-#  if defined(_LIBCPP_GLIBC_PREREQ)
+#  if defined(__clang__)
+#    define _LIBCPP_HAS_C8RTOMB_MBRTOC8 1
+#  elif defined(_LIBCPP_GLIBC_PREREQ)
 #    if _LIBCPP_GLIBC_PREREQ(2, 36) && defined(__cpp_char8_t)
 #      define _LIBCPP_HAS_C8RTOMB_MBRTOC8 1
 #    else
diff --git a/libcxx/test/std/depr/depr.c.headers/uchar_h.compile.pass.cpp b/libcxx/test/std/depr/depr.c.headers/uchar_h.compile.pass.cpp
index a1560c8ee5853..c448ba83f4b38 100644
--- a/libcxx/test/std/depr/depr.c.headers/uchar_h.compile.pass.cpp
+++ b/libcxx/test/std/depr/depr.c.headers/uchar_h.compile.pass.cpp
@@ -23,11 +23,6 @@
 // __STDC_UTF_16__ may or may not be defined by the C standard library
 // __STDC_UTF_32__ may or may not be defined by the C standard library
 
-#if !defined(TEST_HAS_NO_C8RTOMB_MBRTOC8)
-ASSERT_SAME_TYPE(size_t, decltype(mbrtoc8((char8_t*)0, (const char*)0, (size_t)0, (mbstate_t*)0)));
-ASSERT_SAME_TYPE(size_t, decltype(c8rtomb((char*)0, (char8_t)0, (mbstate_t*)0)));
-#endif
-
 ASSERT_SAME_TYPE(size_t, decltype(mbrtoc16((char16_t*)0, (const char*)0, (size_t)0, (mbstate_t*)0)));
 ASSERT_SAME_TYPE(size_t, decltype(c16rtomb((char*)0, (char16_t)0, (mbstate_t*)0)));
 
diff --git a/libcxx/test/std/depr/depr.c.headers/uchar_h_char8_t.compile.pass.cpp b/libcxx/test/std/depr/depr.c.headers/uchar_h_char8_t.compile.pass.cpp
new file mode 100644
index 0000000000000..1c204cbc3f68f
--- /dev/null
+++ b/libcxx/test/std/depr/depr.c.headers/uchar_h_char8_t.compile.pass.cpp
@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03
+
+// The following platforms do not provide mbrtoc8 and c8rtomb so the tests fail
+// XFAIL: target={{.+}}-aix{{.*}}
+// XFAIL: darwin
+// XFAIL: freebsd
+// XFAIL: windows
+// XFAIL: LIBCXX-PICOLIBC-FIXME
+
+// <uchar.h>
+
+#include <uchar.h>
+
+#include "test_macros.h"
+
+#if !defined(TEST_HAS_NO_C8RTOMB_MBRTOC8)
+ASSERT_SAME_TYPE(size_t, decltype(mbrtoc8((char8_t*)0, (const char*)0, (size_t)0, (mbstate_t*)0)));
+ASSERT_SAME_TYPE(size_t, decltype(c8rtomb((char*)0, (char8_t)0, (mbstate_t*)0)));
+#endif
diff --git a/libcxx/test/std/strings/c.strings/cuchar.compile.pass.cpp b/libcxx/test/std/strings/c.strings/cuchar.compile.pass.cpp
index 2076384deb2b2..96b394a9934f8 100644
--- a/libcxx/test/std/strings/c.strings/cuchar.compile.pass.cpp
+++ b/libcxx/test/std/strings/c.strings/cuchar.compile.pass.cpp
@@ -23,11 +23,6 @@
 // __STDC_UTF_16__ may or may not be defined by the C standard library
 // __STDC_UTF_32__ may or may not be defined by the C standard library
 
-#if !defined(TEST_HAS_NO_C8RTOMB_MBRTOC8)
-ASSERT_SAME_TYPE(std::size_t, decltype(std::mbrtoc8((char8_t*)0, (const char*)0, (size_t)0, (mbstate_t*)0)));
-ASSERT_SAME_TYPE(std::size_t, decltype(std::c8rtomb((char*)0, (char8_t)0, (mbstate_t*)0)));
-#endif
-
 ASSERT_SAME_TYPE(std::size_t, decltype(std::mbrtoc16((char16_t*)0, (const char*)0, (size_t)0, (mbstate_t*)0)));
 ASSERT_SAME_TYPE(std::size_t, decltype(std::c16rtomb((char*)0, (char16_t)0, (mbstate_t*)0)));
 
diff --git a/libcxx/test/std/strings/c.strings/cuchar_char8_t.compile.pass.cpp b/libcxx/test/std/strings/c.strings/cuchar_char8_t.compile.pass.cpp
new file mode 100644
index 0000000000000..b0694c2100524
--- /dev/null
+++ b/libcxx/test/std/strings/c.strings/cuchar_char8_t.compile.pass.cpp
@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03
+
+// The following platforms do not provide mbrtoc8 and c8rtomb so the tests fail
+// XFAIL: target={{.+}}-aix{{.*}}
+// XFAIL: darwin
+// XFAIL: freebsd
+// XFAIL: windows
+// XFAIL: LIBCXX-PICOLIBC-FIXME
+
+// <cuchar>
+
+#include <cuchar>
+
+#include "test_macros.h"
+
+#if !defined(TEST_HAS_NO_C8RTOMB_MBRTOC8)
+ASSERT_SAME_TYPE(std::size_t, decltype(std::mbrtoc8((char8_t*)0, (const char*)0, (size_t)0, (mbstate_t*)0)));
+ASSERT_SAME_TYPE(std::size_t, decltype(std::c8rtomb((char*)0, (char8_t)0, (mbstate_t*)0)));
+#endif
diff --git a/libcxx/test/std/strings/c.strings/no_c8rtomb_mbrtoc8.verify.cpp b/libcxx/test/std/strings/c.strings/no_c8rtomb_mbrtoc8.verify.cpp
deleted file mode 100644
index 1d4a225668d80..0000000000000
--- a/libcxx/test/std/strings/c.strings/no_c8rtomb_mbrtoc8.verify.cpp
+++ /dev/null
@@ -1,30 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-
-// UNSUPPORTED: c++03
-
-#include <uchar.h>
-
-#include "test_macros.h"
-
-// When C++ char8_t support is not enabled, definitions of these functions that
-// match the C2X declarations may still be present in the global namespace with
-// a char8_t typedef substituted for the C++ char8_t type. If so, these are not
-// the declarations we are looking for, so don't test for them.
-#if !defined(TEST_HAS_NO_CHAR8_T)
-using U = decltype(::c8rtomb);
-using V = decltype(::mbrtoc8);
-#  if !_LIBCPP_HAS_C8RTOMB_MBRTOC8
-// expected-error at -3 {{no member named 'c8rtomb' in the global namespace}}
-// expected-error at -3 {{no member named 'mbrtoc8' in the global namespace}}
-#  else
-// expected-no-diagnostics
-#  endif
-#else
-// expected-no-diagnostics
-#endif