[llvm-branch-commits] [libcxx] release/18.x: [libc++] Only include <setjmp.h> from the C library if it exists (#81887) (PR #82045)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/82045

Backport d8278b6

Requested by: @ldionne

>From 74fe0854bc9cb159e5a182f511966dd5ddb33915 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2 at gmail.com>
Date: Fri, 16 Feb 2024 16:45:00 -0500
Subject: [PATCH] [libc++] Only include <setjmp.h> from the C library if it
 exists (#81887)

In 2cea1babefbb, we removed the <setjmp.h> header provided by libc++. However, we did not conditionally include the underlying <setjmp.h>
header only if the C library provides one, which we otherwise do consistently (see e.g. 647ddc08f43c).

rdar://122978778
(cherry picked from commit d8278b682386f51dfba204849c624672a3df40c7)
---
 libcxx/include/csetjmp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/libcxx/include/csetjmp b/libcxx/include/csetjmp
index d219c8e6cb2250..9012cad22ebe74 100644
--- a/libcxx/include/csetjmp
+++ b/libcxx/include/csetjmp
@@ -33,7 +33,13 @@ void longjmp(jmp_buf env, int val);
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__config>
 
-#include <setjmp.h>
+// <setjmp.h> is not provided by libc++
+#if __has_include(<setjmp.h>)
+#  include <setjmp.h>
+#  ifdef _LIBCPP_SETJMP_H
+#    error "If libc++ starts defining <setjmp.h>, the __has_include check should move to libc++'s <setjmp.h>"
+#  endif
+#endif
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header