[llvm-branch-commits] [libcxx] release/20.x: [libc++] Avoid including <features.h> on arbitrary platforms (#125587) (PR #127310)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/127310

Backport cffc1ac3491c891ef4f80bcbfa685710e477eeac

Requested by: @ldionne

>From 49edc61061abd15b7b6a240463c3a296e4286569 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2 at gmail.com>
Date: Sat, 15 Feb 2025 10:54:00 +0100
Subject: [PATCH] [libc++] Avoid including <features.h> on arbitrary platforms
 (#125587)

This partially reverts commit 5f2389d4. That commit started checking
whether <features.h> was a valid include unconditionally, however codebases
are free to have such a header on their search path, which breaks compilation.
LLVM libc now provides a more standard way of getting configuration macros
like __LLVM_LIBC__.

After this patch, we only include <features.h> when we're on Linux or
when we're compiling for GPUs.

(cherry picked from commit cffc1ac3491c891ef4f80bcbfa685710e477eeac)
---
 libcxx/include/__configuration/platform.h | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/libcxx/include/__configuration/platform.h b/libcxx/include/__configuration/platform.h
index 2a92ce209b91f..cff99376ee24b 100644
--- a/libcxx/include/__configuration/platform.h
+++ b/libcxx/include/__configuration/platform.h
@@ -30,12 +30,9 @@
 // ... add new file formats here ...
 #endif
 
-// To detect which libc we're using
-#if __has_include(<features.h>)
+// Need to detect which libc we're using if we're on Linux.
+#if defined(__linux__) || defined(__AMDGPU__) || defined(__NVPTX__)
 #  include <features.h>
-#endif
-
-#if defined(__linux__)
 #  if defined(__GLIBC_PREREQ)
 #    define _LIBCPP_GLIBC_PREREQ(a, b) __GLIBC_PREREQ(a, b)
 #  else