[libcxx-commits] [libcxx] [libc++] Allow building libc++ using llvm-libc without locale support (PR #187603)
Jackson Stogel via libcxx-commits
libcxx-commits at lists.llvm.org
Wed Apr 29 08:31:43 PDT 2026
https://github.com/jtstogel updated https://github.com/llvm/llvm-project/pull/187603
>From ccf8240a5da1a595d26e873f64c4eb2b462c51b5 Mon Sep 17 00:00:00 2001
From: jtstogel <jtstogel at google.com>
Date: Tue, 17 Mar 2026 14:51:08 -0700
Subject: [PATCH 1/3] [libc++] Allow building libc++ using llvm-libc without
locale support
---
libcxx/include/CMakeLists.txt | 3 +
libcxx/include/__locale_dir/locale_base_api.h | 2 +
.../include/__locale_dir/support/llvm_libc.h | 62 +++++++++++++++
.../support/no_locale/characters.h | 1 +
.../support/no_locale/conversions.h | 78 +++++++++++++++++++
.../support/no_locale/formatting.h | 50 ++++++++++++
libcxx/include/module.modulemap.in | 3 +
7 files changed, 199 insertions(+)
create mode 100644 libcxx/include/__locale_dir/support/llvm_libc.h
create mode 100644 libcxx/include/__locale_dir/support/no_locale/conversions.h
create mode 100644 libcxx/include/__locale_dir/support/no_locale/formatting.h
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index 53165f0336b2d..a1345d40ef1f6 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -541,9 +541,12 @@ set(files
__locale_dir/support/freebsd.h
__locale_dir/support/fuchsia.h
__locale_dir/support/linux.h
+ __locale_dir/support/llvm_libc.h
__locale_dir/support/netbsd.h
__locale_dir/support/newlib.h
__locale_dir/support/no_locale/characters.h
+ __locale_dir/support/no_locale/conversions.h
+ __locale_dir/support/no_locale/formatting.h
__locale_dir/support/no_locale/strtonum.h
__locale_dir/support/windows.h
__locale_dir/time.h
diff --git a/libcxx/include/__locale_dir/locale_base_api.h b/libcxx/include/__locale_dir/locale_base_api.h
index 26a6069315b33..60d064cbd7bae 100644
--- a/libcxx/include/__locale_dir/locale_base_api.h
+++ b/libcxx/include/__locale_dir/locale_base_api.h
@@ -116,6 +116,8 @@
# include <__locale_dir/support/windows.h>
# elif defined(__Fuchsia__)
# include <__locale_dir/support/fuchsia.h>
+# elif _LIBCPP_LIBC_LLVM_LIBC
+# include <__locale_dir/support/llvm_libc.h>
# elif defined(__linux__)
# include <__locale_dir/support/linux.h>
# elif _LIBCPP_LIBC_NEWLIB
diff --git a/libcxx/include/__locale_dir/support/llvm_libc.h b/libcxx/include/__locale_dir/support/llvm_libc.h
new file mode 100644
index 0000000000000..e2763f03e75e5
--- /dev/null
+++ b/libcxx/include/__locale_dir/support/llvm_libc.h
@@ -0,0 +1,62 @@
+//===-----------------------------------------------------------------------===//
+//
+// 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___LOCALE_DIR_SUPPORT_LLVM_LIBC_H
+#define _LIBCPP___LOCALE_DIR_SUPPORT_LLVM_LIBC_H
+
+#include <__config>
+#include <clocale>
+#include <cstdio>
+#include <cstdlib>
+#include <ctype.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __locale {
+
+using __locale_t _LIBCPP_NODEBUG = ::locale_t;
+
+#define _LIBCPP_COLLATE_MASK LC_COLLATE_MASK
+#define _LIBCPP_CTYPE_MASK LC_CTYPE_MASK
+#define _LIBCPP_MONETARY_MASK LC_MONETARY_MASK
+#define _LIBCPP_NUMERIC_MASK LC_NUMERIC_MASK
+#define _LIBCPP_TIME_MASK LC_TIME_MASK
+#define _LIBCPP_MESSAGES_MASK LC_MESSAGES_MASK
+#define _LIBCPP_ALL_MASK LC_ALL_MASK
+#define _LIBCPP_LC_ALL LC_ALL
+
+#if defined(_LIBCPP_BUILDING_LIBRARY)
+using __lconv_t _LIBCPP_NODEBUG = std::lconv;
+
+inline _LIBCPP_HIDE_FROM_ABI __locale_t __newlocale(int __category_mask, const char* __locale, __locale_t __base) {
+ return ::newlocale(__category_mask, __locale, __base);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI void __freelocale(__locale_t __loc) { ::freelocale(__loc); }
+
+inline _LIBCPP_HIDE_FROM_ABI char* __setlocale(int __category, char const* __locale) {
+ return ::setlocale(__category, __locale);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI __lconv_t* __localeconv(__locale_t&) {
+ return std::localeconv();
+}
+#endif // _LIBCPP_BUILDING_LIBRARY
+
+} // namespace __locale
+_LIBCPP_END_NAMESPACE_STD
+
+#include <__locale_dir/support/no_locale/characters.h>
+#include <__locale_dir/support/no_locale/conversions.h>
+#include <__locale_dir/support/no_locale/formatting.h>
+#include <__locale_dir/support/no_locale/strtonum.h>
+
+#endif // _LIBCPP___LOCALE_DIR_SUPPORT_LLVM_LIBC_H
diff --git a/libcxx/include/__locale_dir/support/no_locale/characters.h b/libcxx/include/__locale_dir/support/no_locale/characters.h
index e0755d1a7152a..52e842d8f494f 100644
--- a/libcxx/include/__locale_dir/support/no_locale/characters.h
+++ b/libcxx/include/__locale_dir/support/no_locale/characters.h
@@ -16,6 +16,7 @@
#include <cstring>
#include <ctime>
#if _LIBCPP_HAS_WIDE_CHARACTERS
+# include <cwchar>
# include <cwctype>
#endif
diff --git a/libcxx/include/__locale_dir/support/no_locale/conversions.h b/libcxx/include/__locale_dir/support/no_locale/conversions.h
new file mode 100644
index 0000000000000..71b704409e9cf
--- /dev/null
+++ b/libcxx/include/__locale_dir/support/no_locale/conversions.h
@@ -0,0 +1,78 @@
+//===-----------------------------------------------------------------------===//
+//
+// 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___LOCALE_DIR_SUPPORT_NO_LOCALE_CONVERSIONS_H
+#define _LIBCPP___LOCALE_DIR_SUPPORT_NO_LOCALE_CONVERSIONS_H
+
+#include <__config>
+#include <__cstddef/size_t.h>
+#include <__std_mbstate_t.h>
+#include <cstdlib>
+#if _LIBCPP_HAS_WIDE_CHARACTERS
+# include <cwchar>
+#endif
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __locale {
+
+#if defined(_LIBCPP_BUILDING_LIBRARY)
+inline _LIBCPP_HIDE_FROM_ABI decltype(MB_CUR_MAX) __mb_len_max(__locale_t) {
+ return MB_CUR_MAX;
+}
+
+# if _LIBCPP_HAS_WIDE_CHARACTERS
+inline _LIBCPP_HIDE_FROM_ABI wint_t __btowc(int __c, __locale_t) {
+ return std::btowc(__c);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI int __wctob(wint_t __c, __locale_t) {
+ return std::wctob(__c);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI size_t
+__wcsnrtombs(char* __dest, const wchar_t** __src, size_t __nwc, size_t __len, mbstate_t* __ps, __locale_t) {
+ return ::wcsnrtombs(__dest, __src, __nwc, __len, __ps); // Non-standard
+}
+
+inline _LIBCPP_HIDE_FROM_ABI size_t __wcrtomb(char* __s, wchar_t __wc, mbstate_t* __ps, __locale_t) {
+ return std::wcrtomb(__s, __wc, __ps);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI size_t
+__mbsnrtowcs(wchar_t* __dest, const char** __src, size_t __nms, size_t __len, mbstate_t* __ps, __locale_t) {
+ return ::mbsnrtowcs(__dest, __src, __nms, __len, __ps); // Non-standard
+}
+
+inline _LIBCPP_HIDE_FROM_ABI size_t
+__mbrtowc(wchar_t* __pwc, const char* __s, size_t __n, mbstate_t* __ps, __locale_t) {
+ return std::mbrtowc(__pwc, __s, __n, __ps);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI int __mbtowc(wchar_t* __pwc, const char* __pmb, size_t __max, __locale_t) {
+ return std::mbtowc(__pwc, __pmb, __max);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI size_t __mbrlen(const char* __s, size_t __n, mbstate_t* __ps, __locale_t) {
+ return std::mbrlen(__s, __n, __ps);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI size_t
+__mbsrtowcs(wchar_t* __dest, const char** __src, size_t __len, mbstate_t* __ps, __locale_t) {
+ return std::mbsrtowcs(__dest, __src, __len, __ps);
+}
+# endif // _LIBCPP_HAS_WIDE_CHARACTERS
+#endif // _LIBCPP_BUILDING_LIBRARY
+
+} // namespace __locale
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___LOCALE_DIR_SUPPORT_NO_LOCALE_CONVERSIONS_H
diff --git a/libcxx/include/__locale_dir/support/no_locale/formatting.h b/libcxx/include/__locale_dir/support/no_locale/formatting.h
new file mode 100644
index 0000000000000..7185e9a4e6004
--- /dev/null
+++ b/libcxx/include/__locale_dir/support/no_locale/formatting.h
@@ -0,0 +1,50 @@
+//===-----------------------------------------------------------------------===//
+//
+// 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___LOCALE_DIR_SUPPORT_NO_LOCALE_FORMATTING_H
+#define _LIBCPP___LOCALE_DIR_SUPPORT_NO_LOCALE_FORMATTING_H
+
+#include <__config>
+#include <__utility/forward.h>
+#include <cstdio>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __locale {
+
+_LIBCPP_DIAGNOSTIC_PUSH
+_LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wgcc-compat")
+_LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wformat-nonliteral") // GCC doesn't support [[gnu::format]] on variadic templates
+#ifdef _LIBCPP_COMPILER_CLANG_BASED
+# define _LIBCPP_VARIADIC_ATTRIBUTE_FORMAT(...) _LIBCPP_ATTRIBUTE_FORMAT(__VA_ARGS__)
+#else
+# define _LIBCPP_VARIADIC_ATTRIBUTE_FORMAT(...) /* nothing */
+#endif
+
+template <class... _Args>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_VARIADIC_ATTRIBUTE_FORMAT(__printf__, 4, 5) int __snprintf(
+ char* __s, size_t __n, __locale_t, const char* __format, _Args&&... __args) {
+ return std::snprintf(__s, __n, __format, std::forward<_Args>(__args)...);
+}
+
+template <class... _Args>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_VARIADIC_ATTRIBUTE_FORMAT(__printf__, 3, 4) int __asprintf(
+ char** __s, __locale_t, const char* __format, _Args&&... __args) {
+ return ::asprintf(__s, __format, std::forward<_Args>(__args)...); // non-standard
+}
+
+_LIBCPP_DIAGNOSTIC_POP
+#undef _LIBCPP_VARIADIC_ATTRIBUTE_FORMAT
+
+} // namespace __locale
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___LOCALE_DIR_SUPPORT_NO_LOCALE_FORMATTING_H
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
index d6e8289b7c8b0..6bffb67bfb683 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -1604,7 +1604,10 @@ module std [system] {
textual header "__locale_dir/support/freebsd.h"
textual header "__locale_dir/support/fuchsia.h"
textual header "__locale_dir/support/linux.h"
+ textual header "__locale_dir/support/llvm_libc.h"
textual header "__locale_dir/support/netbsd.h"
+ textual header "__locale_dir/support/no_locale/conversions.h"
+ textual header "__locale_dir/support/no_locale/formatting.h"
textual header "__locale_dir/support/newlib.h"
textual header "__locale_dir/support/no_locale/characters.h"
textual header "__locale_dir/support/no_locale/strtonum.h"
>From 48e14869c35743024a7a7e51137f9ce61817f2fa Mon Sep 17 00:00:00 2001
From: jtstogel <jtstogel at google.com>
Date: Thu, 19 Mar 2026 09:54:13 -0700
Subject: [PATCH 2/3] Include LLVM-libc's mbstate_t.h
---
libcxx/include/__mbstate_t.h | 2 ++
1 file changed, 2 insertions(+)
diff --git a/libcxx/include/__mbstate_t.h b/libcxx/include/__mbstate_t.h
index c23ea7113ca70..3dae03e89ab68 100644
--- a/libcxx/include/__mbstate_t.h
+++ b/libcxx/include/__mbstate_t.h
@@ -39,6 +39,8 @@
# define __NEED_mbstate_t
# include <bits/alltypes.h>
# undef __NEED_mbstate_t
+#elif _LIBCPP_LIBC_LLVM_LIBC
+# include <llvm-libc-types/mbstate_t.h>
#elif __has_include(<bits/types/mbstate_t.h>)
# include <bits/types/mbstate_t.h> // works on most Unixes
#elif __has_include(<sys/_types/_mbstate_t.h>)
>From 4b9aad9e8c9b8d44821635a21110c9bc22137707 Mon Sep 17 00:00:00 2001
From: jtstogel <jtstogel at google.com>
Date: Thu, 19 Mar 2026 16:39:34 -0700
Subject: [PATCH 3/3] Format headers.
---
libcxx/include/__locale_dir/support/llvm_libc.h | 4 +---
.../__locale_dir/support/no_locale/conversions.h | 16 +++++-----------
2 files changed, 6 insertions(+), 14 deletions(-)
diff --git a/libcxx/include/__locale_dir/support/llvm_libc.h b/libcxx/include/__locale_dir/support/llvm_libc.h
index e2763f03e75e5..1ce1c443d87ed 100644
--- a/libcxx/include/__locale_dir/support/llvm_libc.h
+++ b/libcxx/include/__locale_dir/support/llvm_libc.h
@@ -46,9 +46,7 @@ inline _LIBCPP_HIDE_FROM_ABI char* __setlocale(int __category, char const* __loc
return ::setlocale(__category, __locale);
}
-inline _LIBCPP_HIDE_FROM_ABI __lconv_t* __localeconv(__locale_t&) {
- return std::localeconv();
-}
+inline _LIBCPP_HIDE_FROM_ABI __lconv_t* __localeconv(__locale_t&) { return std::localeconv(); }
#endif // _LIBCPP_BUILDING_LIBRARY
} // namespace __locale
diff --git a/libcxx/include/__locale_dir/support/no_locale/conversions.h b/libcxx/include/__locale_dir/support/no_locale/conversions.h
index 71b704409e9cf..64a50df4a50b9 100644
--- a/libcxx/include/__locale_dir/support/no_locale/conversions.h
+++ b/libcxx/include/__locale_dir/support/no_locale/conversions.h
@@ -25,22 +25,16 @@ _LIBCPP_BEGIN_NAMESPACE_STD
namespace __locale {
#if defined(_LIBCPP_BUILDING_LIBRARY)
-inline _LIBCPP_HIDE_FROM_ABI decltype(MB_CUR_MAX) __mb_len_max(__locale_t) {
- return MB_CUR_MAX;
-}
+inline _LIBCPP_HIDE_FROM_ABI decltype(MB_CUR_MAX) __mb_len_max(__locale_t) { return MB_CUR_MAX; }
# if _LIBCPP_HAS_WIDE_CHARACTERS
-inline _LIBCPP_HIDE_FROM_ABI wint_t __btowc(int __c, __locale_t) {
- return std::btowc(__c);
-}
+inline _LIBCPP_HIDE_FROM_ABI wint_t __btowc(int __c, __locale_t) { return std::btowc(__c); }
-inline _LIBCPP_HIDE_FROM_ABI int __wctob(wint_t __c, __locale_t) {
- return std::wctob(__c);
-}
+inline _LIBCPP_HIDE_FROM_ABI int __wctob(wint_t __c, __locale_t) { return std::wctob(__c); }
inline _LIBCPP_HIDE_FROM_ABI size_t
__wcsnrtombs(char* __dest, const wchar_t** __src, size_t __nwc, size_t __len, mbstate_t* __ps, __locale_t) {
- return ::wcsnrtombs(__dest, __src, __nwc, __len, __ps); // Non-standard
+ return ::wcsnrtombs(__dest, __src, __nwc, __len, __ps); // Non-standard
}
inline _LIBCPP_HIDE_FROM_ABI size_t __wcrtomb(char* __s, wchar_t __wc, mbstate_t* __ps, __locale_t) {
@@ -49,7 +43,7 @@ inline _LIBCPP_HIDE_FROM_ABI size_t __wcrtomb(char* __s, wchar_t __wc, mbstate_t
inline _LIBCPP_HIDE_FROM_ABI size_t
__mbsnrtowcs(wchar_t* __dest, const char** __src, size_t __nms, size_t __len, mbstate_t* __ps, __locale_t) {
- return ::mbsnrtowcs(__dest, __src, __nms, __len, __ps); // Non-standard
+ return ::mbsnrtowcs(__dest, __src, __nms, __len, __ps); // Non-standard
}
inline _LIBCPP_HIDE_FROM_ABI size_t
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