From f00136016c245d43aec97a2770a6dc2c263d0467 Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser@berlin.de>
Date: Sat, 24 Feb 2024 14:47:48 +0100
Subject: [PATCH] [libc++] Remove unnecessary includes from <atomic>

---
 libcxx/include/__atomic/aliases.h                | 1 -
 libcxx/include/__config                          | 5 +++++
 libcxx/include/__thread/support/pthread.h        | 5 ++++-
 libcxx/include/atomic                            | 1 +
 libcxx/test/libcxx/transitive_includes/cxx23.csv | 1 -
 libcxx/test/libcxx/transitive_includes/cxx26.csv | 1 -
 6 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/libcxx/include/__atomic/aliases.h b/libcxx/include/__atomic/aliases.h
index 0fa289de54b0f1..a87099802737aa 100644
--- a/libcxx/include/__atomic/aliases.h
+++ b/libcxx/include/__atomic/aliases.h
@@ -18,7 +18,6 @@
 #include <__type_traits/make_unsigned.h>
 #include <cstddef>
 #include <cstdint>
-#include <cstdlib>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
diff --git a/libcxx/include/__config b/libcxx/include/__config
index 0797880cb2f5da..2035bb1ca61840 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -460,6 +460,11 @@ _LIBCPP_HARDENING_MODE_DEBUG
 #    define __has_constexpr_builtin(x) 0
 #  endif
 
+// This checks wheter a Clang module is built
+#  ifndef __building_module
+#    define __building_module(...) 0
+#  endif
+
 // '__is_identifier' returns '0' if '__x' is a reserved identifier provided by
 // the compiler and '1' otherwise.
 #  ifndef __is_identifier
diff --git a/libcxx/include/__thread/support/pthread.h b/libcxx/include/__thread/support/pthread.h
index d0b8367e448f48..d8e3f938ddf629 100644
--- a/libcxx/include/__thread/support/pthread.h
+++ b/libcxx/include/__thread/support/pthread.h
@@ -30,7 +30,10 @@
 // so libc++'s <math.h> usually absorbs atomic_wide_counter.h into the
 // module with <math.h> and makes atomic_wide_counter.h invisible.
 // Include <math.h> here to work around that.
-#include <math.h>
+// This checks wheter a Clang module is built
+#if __building_module(std)
+#  include <math.h>
+#endif
 
 #ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
 #  pragma GCC system_header
diff --git a/libcxx/include/atomic b/libcxx/include/atomic
index 2e8f5b521a55eb..2dac69377b77f0 100644
--- a/libcxx/include/atomic
+++ b/libcxx/include/atomic
@@ -620,6 +620,7 @@ template <class T>
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
 #  include <cmath>
 #  include <compare>
+#  include <cstdlib>
 #  include <cstring>
 #  include <type_traits>
 #endif
diff --git a/libcxx/test/libcxx/transitive_includes/cxx23.csv b/libcxx/test/libcxx/transitive_includes/cxx23.csv
index 44b5f78beea48b..49b3ac265487d7 100644
--- a/libcxx/test/libcxx/transitive_includes/cxx23.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx23.csv
@@ -30,7 +30,6 @@ array stdexcept
 array version
 atomic cstddef
 atomic cstdint
-atomic cstdlib
 atomic cstring
 atomic ctime
 atomic limits
diff --git a/libcxx/test/libcxx/transitive_includes/cxx26.csv b/libcxx/test/libcxx/transitive_includes/cxx26.csv
index 44b5f78beea48b..49b3ac265487d7 100644
--- a/libcxx/test/libcxx/transitive_includes/cxx26.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx26.csv
@@ -30,7 +30,6 @@ array stdexcept
 array version
 atomic cstddef
 atomic cstdint
-atomic cstdlib
 atomic cstring
 atomic ctime
 atomic limits