[libc++] Add a thread-safe version of std::lgamma in the dylib

libcxx/CMakeLists.txt

@@ -681,6 +681,10 @@ function(cxx_link_system_libraries target)
     target_link_libraries(${target} PRIVATE atomic)
   endif()
 
+  if (LIBCXX_HAS_MATH_LIB)
+    target_link_libraries(${target} PRIVATE m)
+  endif()
+
   if (MINGW)
     target_link_libraries(${target} PRIVATE "${MINGW_LIBRARIES}")
   endif()

libcxx/cmake/config-ix.cmake

@@ -110,24 +110,32 @@ if(WIN32 AND NOT MINGW)
   set(LIBCXX_HAS_PTHREAD_LIB NO)
   set(LIBCXX_HAS_RT_LIB NO)
   set(LIBCXX_HAS_ATOMIC_LIB NO)
+  set(LIBCXX_HAS_MATH_LIB NO)
 elseif(APPLE)
   set(LIBCXX_HAS_PTHREAD_LIB NO)
   set(LIBCXX_HAS_RT_LIB NO)
   set(LIBCXX_HAS_ATOMIC_LIB NO)
+  set(LIBCXX_HAS_MATH_LIB NO)
 elseif(FUCHSIA)
   set(LIBCXX_HAS_PTHREAD_LIB NO)
   set(LIBCXX_HAS_RT_LIB NO)
   check_library_exists(atomic __atomic_fetch_add_8 "" LIBCXX_HAS_ATOMIC_LIB)
+  set(LIBCXX_HAS_MATH_LIB NO)
 elseif(ANDROID)
   set(LIBCXX_HAS_PTHREAD_LIB NO)
   set(LIBCXX_HAS_RT_LIB NO)
   set(LIBCXX_HAS_ATOMIC_LIB NO)
+  set(LIBCXX_HAS_MATH_LIB NO)
 elseif(PICOLIBC)
   set(LIBCXX_HAS_PTHREAD_LIB NO)
   set(LIBCXX_HAS_RT_LIB NO)
   set(LIBCXX_HAS_ATOMIC_LIB NO)
+  set(LIBCXX_HAS_MATH_LIB NO)
 else()
   check_library_exists(pthread pthread_create "" LIBCXX_HAS_PTHREAD_LIB)
   check_library_exists(rt clock_gettime "" LIBCXX_HAS_RT_LIB)
   check_library_exists(atomic __atomic_fetch_add_8 "" LIBCXX_HAS_ATOMIC_LIB)
+  if (CMAKE_SYSTEM_NAME STREQUAL "Linux" AND CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+    set(LIBCXX_HAS_MATH_LIB ON)
+  endif()
 endif()

libcxx/include/__configuration/availability.h

@@ -84,6 +84,9 @@
 // in all versions of the library are available.
 #if !_LIBCPP_HAS_VENDOR_AVAILABILITY_ANNOTATIONS
 
+#  define _LIBCPP_INTRODUCED_IN_LLVM_22 1
+#  define _LIBCPP_INTRODUCED_IN_LLVM_22_ATTRIBUTE /* nothing */
+
 #  define _LIBCPP_INTRODUCED_IN_LLVM_21 1
 #  define _LIBCPP_INTRODUCED_IN_LLVM_21_ATTRIBUTE /* nothing */
 
@@ -112,6 +115,11 @@
 
 // clang-format off
 
+// LLVM 22
+// TODO: Fill this in
+#  define _LIBCPP_INTRODUCED_IN_LLVM_22 0
+#  define _LIBCPP_INTRODUCED_IN_LLVM_22_ATTRIBUTE __attribute__((unavailable))
+
 // LLVM 21
 // TODO: Fill this in
 #  define _LIBCPP_INTRODUCED_IN_LLVM_21 0
@@ -317,6 +325,11 @@
 #define _LIBCPP_AVAILABILITY_HAS_BAD_FUNCTION_CALL_GOOD_WHAT_MESSAGE _LIBCPP_INTRODUCED_IN_LLVM_21
 // No attribute, since we've had bad_function_call::what() in the headers before
 
+// This controls whether we provide an implementation of a thread safe variant of the `std::lgamma`
+// function in the dylib.
+#define _LIBCPP_AVAILABILITY_HAS_THREAD_SAFE_LGAMMA _LIBCPP_INTRODUCED_IN_LLVM_22
+// No attribute, since we call ::lgamma_r instead
+
 // Define availability attributes that depend on both
 // _LIBCPP_HAS_EXCEPTIONS and _LIBCPP_HAS_RTTI.
 #if !_LIBCPP_HAS_EXCEPTIONS || !_LIBCPP_HAS_RTTI

libcxx/include/__math/gamma.h

@@ -57,6 +57,31 @@ inline _LIBCPP_HIDE_FROM_ABI double tgamma(_A1 __x) _NOEXCEPT {
 
 } // namespace __math
 
+// __lgamma_r
+
+struct __lgamma_result {
+  double __result;
+  int __sign;
+};
+
+#if _LIBCPP_AVAILABILITY_HAS_THREAD_SAFE_LGAMMA
+_LIBCPP_EXPORTED_FROM_ABI __lgamma_result __lgamma_thread_safe_impl(double) _NOEXCEPT;
+
+inline _LIBCPP_HIDE_FROM_ABI __lgamma_result __lgamma_thread_safe(double __d) _NOEXCEPT {
+  return std::__lgamma_thread_safe_impl(__d);
+}
+#else
+// When deploying to older targets, call `lgamma_r` directly but avoid declaring the actual
+// function since different platforms declare the function slightly differently.
+double __lgamma_r_shim(double, int*) _NOEXCEPT __asm__("lgamma_r");
+
+inline _LIBCPP_HIDE_FROM_ABI __lgamma_result __lgamma_thread_safe(double __d) _NOEXCEPT {
+  int __sign;
+  double __res = std::__lgamma_r_shim(__d, &__sign);
+  return __lgamma_result{__res, __sign};
+}
+#endif
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___MATH_GAMMA_H

libcxx/include/__random/binomial_distribution.h

@@ -10,6 +10,7 @@
 #define _LIBCPP___RANDOM_BINOMIAL_DISTRIBUTION_H
 
 #include <__config>
+#include <__math/gamma.h>
 #include <__random/is_valid.h>
 #include <__random/uniform_real_distribution.h>
 #include <cmath>
@@ -97,39 +98,13 @@ class binomial_distribution {
   }
 };
 
-// Some libc declares the math functions to be `noexcept`.
-#if defined(_LIBCPP_GLIBC_PREREQ)
-#  if _LIBCPP_GLIBC_PREREQ(2, 8)
-#    define _LIBCPP_LGAMMA_R_NOEXCEPT _NOEXCEPT
-#  else
-#    define _LIBCPP_LGAMMA_R_NOEXCEPT
-#  endif
-#elif defined(__LLVM_LIBC__)
-#  define _LIBCPP_LGAMMA_R_NOEXCEPT _NOEXCEPT
-#else
-#  define _LIBCPP_LGAMMA_R_NOEXCEPT
-#endif
-
-#if !defined(_LIBCPP_MSVCRT_LIKE)
-extern "C" double lgamma_r(double, int*) _LIBCPP_LGAMMA_R_NOEXCEPT;
-#endif
-
-inline _LIBCPP_HIDE_FROM_ABI double __libcpp_lgamma(double __d) {
-#if defined(_LIBCPP_MSVCRT_LIKE)
-  return lgamma(__d);
-#else
-  int __sign;
-  return lgamma_r(__d, &__sign);
-#endif
-}
-
 template <class _IntType>
 binomial_distribution<_IntType>::param_type::param_type(result_type __t, double __p) : __t_(__t), __p_(__p) {
   if (0 < __p_ && __p_ < 1) {
     __r0_ = static_cast<result_type>((__t_ + 1) * __p_);
-    __pr_ = std::exp(
-        std::__libcpp_lgamma(__t_ + 1.) - std::__libcpp_lgamma(__r0_ + 1.) - std::__libcpp_lgamma(__t_ - __r0_ + 1.) +
-        __r0_ * std::log(__p_) + (__t_ - __r0_) * std::log(1 - __p_));
+    __pr_ = std::exp(std::__lgamma_thread_safe(__t_ + 1.).__result - std::__lgamma_thread_safe(__r0_ + 1.).__result -
+                     std::__lgamma_thread_safe(__t_ - __r0_ + 1.).__result + __r0_ * std::log(__p_) +
+                     (__t_ - __r0_) * std::log(1 - __p_));
     __odds_ratio_ = __p_ / (1 - __p_);
   }
 }

libcxx/lib/abi/CHANGELOG.TXT

@@ -16,6 +16,16 @@ New entries should be added directly below the "Version" header.
 Version 22.0
 ------------
 
+* [libc++] Add a thread-safe version of std::lgamma in the dylib
+
+  This patch adds a new function __lgamma_thread_safe in the dylib to avoid having to redeclare
+  ::lgamma_r within libc++'s own headers. This merely introduces a new symbol so it's not an ABI
+  break.
+
+  All platforms
+  -------------
+  Symbol added: _ZNSt3__125__lgamma_thread_safe_implEd
+
 * [libc++] Remove __time_get_storage::{__analyze,init} from the ABI
 
   These functions have never been used outside the dylib, so there is no point in exporting them.

libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist

@@ -1692,6 +1692,7 @@
 {'is_defined': True, 'name': '__ZNSt3__15wcoutE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__16__itoa8__u32toaEjPc', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__16__itoa8__u64toaEyPc', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__125__lgamma_thread_safe_implEd', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__16__sortIRNS_6__lessIaaEEPaEEvT0_S5_T_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__16__sortIRNS_6__lessIccEEPcEEvT0_S5_T_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__16__sortIRNS_6__lessIddEEPdEEvT0_S5_T_', 'type': 'FUNC'}

libcxx/lib/abi/i686-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist

@@ -1329,6 +1329,7 @@
 {'is_defined': True, 'name': '_ZNSt6__ndk16__clocEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk16__itoa8__u32toaEjPc', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk16__itoa8__u64toaEyPc', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt6__ndk16__math25__lgamma_thread_safe_implEd', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk16__sortIRNS_6__lessIaaEEPaEEvT0_S5_T_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk16__sortIRNS_6__lessIccEEPcEEvT0_S5_T_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk16__sortIRNS_6__lessIddEEPdEEvT0_S5_T_', 'type': 'FUNC'}

libcxx/lib/abi/powerpc-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist

@@ -677,6 +677,7 @@
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__16__clocEv', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__16__itoa8__u32toaEjPc', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__16__itoa8__u64toaEyPc', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
+{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__125__lgamma_thread_safe_implEd', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__16chrono12steady_clock3nowEv', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__16chrono12system_clock11from_time_tEi', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__16chrono12system_clock3nowEv', 'storage_mapping_class': 'DS', 'type': 'FUNC'}

libcxx/lib/abi/powerpc64-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist

@@ -677,6 +677,7 @@
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__16__clocEv', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__16__itoa8__u32toaEjPc', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__16__itoa8__u64toaEmPc', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
+{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__125__lgamma_thread_safe_implEd', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__16chrono12steady_clock3nowEv', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__16chrono12system_clock11from_time_tEl', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__16chrono12system_clock3nowEv', 'storage_mapping_class': 'DS', 'type': 'FUNC'}

libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist

@@ -1691,6 +1691,7 @@
 {'is_defined': True, 'name': '__ZNSt3__15wcoutE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__16__itoa8__u32toaEjPc', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__16__itoa8__u64toaEyPc', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__125__lgamma_thread_safe_implEd', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__16__sortIRNS_6__lessIaaEEPaEEvT0_S5_T_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__16__sortIRNS_6__lessIccEEPcEEvT0_S5_T_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__16__sortIRNS_6__lessIddEEPdEEvT0_S5_T_', 'type': 'FUNC'}

libcxx/lib/abi/x86_64-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist

@@ -1329,6 +1329,7 @@
 {'is_defined': True, 'name': '_ZNSt6__ndk16__clocEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk16__itoa8__u32toaEjPc', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk16__itoa8__u64toaEmPc', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt6__ndk16__math25__lgamma_thread_safe_implEd', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk16__sortIRNS_6__lessIaaEEPaEEvT0_S5_T_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk16__sortIRNS_6__lessIccEEPcEEvT0_S5_T_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk16__sortIRNS_6__lessIddEEPdEEvT0_S5_T_', 'type': 'FUNC'}

libcxx/lib/abi/x86_64-unknown-freebsd.libcxxabi.v1.stable.exceptions.nonew.abilist

@@ -1342,6 +1342,7 @@
 {'is_defined': True, 'name': '_ZNSt3__15wcoutE', 'size': 384, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZNSt3__16__itoa8__u32toaEjPc', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__16__itoa8__u64toaEmPc', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__125__lgamma_thread_safe_implEd', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__16__sortIRNS_6__lessIaaEEPaEEvT0_S5_T_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__16__sortIRNS_6__lessIccEEPcEEvT0_S5_T_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__16__sortIRNS_6__lessIddEEPdEEvT0_S5_T_', 'type': 'FUNC'}

libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.nonew.abilist

@@ -1341,6 +1341,7 @@
 {'is_defined': True, 'name': '_ZNSt3__16__clocEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__16__itoa8__u32toaEjPc', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__16__itoa8__u64toaEmPc', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__125__lgamma_thread_safe_implEd', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__16__sortIRNS_6__lessIaaEEPaEEvT0_S5_T_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__16__sortIRNS_6__lessIccEEPcEEvT0_S5_T_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__16__sortIRNS_6__lessIddEEPdEEvT0_S5_T_', 'type': 'FUNC'}

libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.noexceptions.nonew.abilist

@@ -1312,6 +1312,7 @@
 {'is_defined': True, 'name': '_ZNSt3__16__clocEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__16__itoa8__u32toaEjPc', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__16__itoa8__u64toaEmPc', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__125__lgamma_thread_safe_implEd', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__16__sortIRNS_6__lessIaaEEPaEEvT0_S5_T_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__16__sortIRNS_6__lessIccEEPcEEvT0_S5_T_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__16__sortIRNS_6__lessIddEEPdEEvT0_S5_T_', 'type': 'FUNC'}

libcxx/src/CMakeLists.txt

@@ -30,6 +30,7 @@ set(LIBCXX_SOURCES
   include/ryu/ryu.h
   include/to_chars_floating_point.h
   include/from_chars_floating_point.h
+  math.cpp
   memory.cpp
   memory_resource.cpp
   new_handler.cpp

libcxx/src/math.cpp

@@ -0,0 +1,24 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifdef __APPLE__
+#  define _REENTRANT
+#endif
+
+#include <cmath>
+#include <math.h> // for lgamma_r
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+__lgamma_result __lgamma_thread_safe_impl(double __d) noexcept {
+  int __sign;
+  double __result = ::lgamma_r(__d, &__sign);
+  return __lgamma_result{__result, __sign};
+}
+
+_LIBCPP_END_NAMESPACE_STD