[llvm-branch-commits] [libc] release/20.x: [libc] Move __LLVM_LIBC__ define to __llvm-libc-common.h (#126877) (PR #126960)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/126960

Backport b0d782080529cf5d422847e1f91f29bd7c62f691

Requested by: @petrhosek

>From 87587f925442d6369a7d511426a55ad50f3141ea Mon Sep 17 00:00:00 2001
From: Petr Hosek <phosek at google.com>
Date: Wed, 12 Feb 2025 11:37:07 -0800
Subject: [PATCH] [libc] Move __LLVM_LIBC__ define to __llvm-libc-common.h
 (#126877)

Relying on features.h is problematic since codebases are free to have
such a header on their search path, which breaks compilation. libc
should instead provide a more standard way of getting __LLVM_LIBC__.
Since __llvm-libc-common.h is included from all libc headers, defining
__LLVM_LIBC__ there ensures that this define is available whenever any
of the standard header is included.

(cherry picked from commit b0d782080529cf5d422847e1f91f29bd7c62f691)
---
 libc/include/__llvm-libc-common.h               | 2 ++
 libc/include/llvm-libc-macros/features-macros.h | 2 --
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/libc/include/__llvm-libc-common.h b/libc/include/__llvm-libc-common.h
index b5a23c5765f4d..9112d1ebe302c 100644
--- a/libc/include/__llvm-libc-common.h
+++ b/libc/include/__llvm-libc-common.h
@@ -9,6 +9,8 @@
 #ifndef LLVM_LIBC_COMMON_H
 #define LLVM_LIBC_COMMON_H
 
+#define __LLVM_LIBC__ 1
+
 #ifdef __cplusplus
 
 #undef __BEGIN_C_DECLS
diff --git a/libc/include/llvm-libc-macros/features-macros.h b/libc/include/llvm-libc-macros/features-macros.h
index 5bc87a68fc0ba..f87ae4ad12408 100644
--- a/libc/include/llvm-libc-macros/features-macros.h
+++ b/libc/include/llvm-libc-macros/features-macros.h
@@ -9,6 +9,4 @@
 #ifndef LLVM_LIBC_MACROS_FEATURES_MACROS_H
 #define LLVM_LIBC_MACROS_FEATURES_MACROS_H
 
-#define __LLVM_LIBC__ 1
-
 #endif // LLVM_LIBC_MACROS_FEATURES_MACROS_H