[libc-commits] [libc] [libc] Add simple features.h with implementation macro (PR #69402)

[via libc-commits]

https://github.com/alfredfo created https://github.com/llvm/llvm-project/pull/69402

In the future this should probably be autogenerated so it defines library version.

Only added config/linux/* at the moment with an
if(LLVM_LIBC_FULL_BUILD statement as I don't think this makes sense for overlay builds.

See: Discussion in #libc https://discord.com/channels/636084430946959380/636732994891284500/1163979080979460176

@michaelrj-google

>From c699b1c868196359bff14b2fc782083b24586d18 Mon Sep 17 00:00:00 2001
From: Alfred Persson Forsberg <cat at catcream.org>
Date: Wed, 18 Oct 2023 02:30:09 +0200
Subject: [PATCH] [libc] Add simple features.h with implementation macro

In the future this should probably be autogenerated so it defines
library version.

Only added config/linux/* at the moment with an
if(LLVM_LIBC_FULL_BUILD statement as I don't think this makes sense
for overlay builds.
---
 libc/config/linux/aarch64/headers.txt           |  6 ++++++
 libc/config/linux/riscv/headers.txt             |  6 ++++++
 libc/config/linux/x86_64/headers.txt            |  6 ++++++
 libc/include/CMakeLists.txt                     |  9 +++++++++
 libc/include/features.h.def                     | 17 +++++++++++++++++
 libc/include/llvm-libc-macros/CMakeLists.txt    |  6 ++++++
 libc/include/llvm-libc-macros/features-macros.h | 14 ++++++++++++++
 7 files changed, 64 insertions(+)
 create mode 100644 libc/include/features.h.def
 create mode 100644 libc/include/llvm-libc-macros/features-macros.h

diff --git a/libc/config/linux/aarch64/headers.txt b/libc/config/linux/aarch64/headers.txt
index 6e30c7c29b2c4bf..75016344aba1d46 100644
--- a/libc/config/linux/aarch64/headers.txt
+++ b/libc/config/linux/aarch64/headers.txt
@@ -19,3 +19,9 @@ set(TARGET_PUBLIC_HEADERS
     libc.include.time
     libc.include.unistd
 )
+
+if(LLVM_LIBC_FULL_BUILD)
+  list(APPEND TARGET_PUBLIC_HEADERS
+    libc.include.features
+  )
+endif()
diff --git a/libc/config/linux/riscv/headers.txt b/libc/config/linux/riscv/headers.txt
index aaa75a9dd08cbd7..b9b1ee32fa8be07 100644
--- a/libc/config/linux/riscv/headers.txt
+++ b/libc/config/linux/riscv/headers.txt
@@ -39,3 +39,9 @@ set(TARGET_PUBLIC_HEADERS
     libc.include.sys_utsname
     libc.include.sys_wait
 )
+
+if(LLVM_LIBC_FULL_BUILD)
+  list(APPEND TARGET_PUBLIC_HEADERS
+    libc.include.features
+  )
+endif()
diff --git a/libc/config/linux/x86_64/headers.txt b/libc/config/linux/x86_64/headers.txt
index aaa75a9dd08cbd7..b9b1ee32fa8be07 100644
--- a/libc/config/linux/x86_64/headers.txt
+++ b/libc/config/linux/x86_64/headers.txt
@@ -39,3 +39,9 @@ set(TARGET_PUBLIC_HEADERS
     libc.include.sys_utsname
     libc.include.sys_wait
 )
+
+if(LLVM_LIBC_FULL_BUILD)
+  list(APPEND TARGET_PUBLIC_HEADERS
+    libc.include.features
+  )
+endif()
diff --git a/libc/include/CMakeLists.txt b/libc/include/CMakeLists.txt
index fd2cb9351419ca8..9d170603ffa45cd 100644
--- a/libc/include/CMakeLists.txt
+++ b/libc/include/CMakeLists.txt
@@ -46,6 +46,15 @@ add_gen_header(
     .llvm-libc-types.mode_t
 )
 
+add_gen_header(
+  features
+  DEF_FILE features.h.def
+  GEN_HDR features.h
+  DEPENDS
+    .llvm_libc_common_h
+    .llvm-libc-macros.features_macros
+)
+
 add_gen_header(
   fenv
   DEF_FILE fenv.h.def
diff --git a/libc/include/features.h.def b/libc/include/features.h.def
new file mode 100644
index 000000000000000..444a7da3db18f06
--- /dev/null
+++ b/libc/include/features.h.def
@@ -0,0 +1,17 @@
+//===-- C standard library header features.h ---------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_FEATURES_H
+#define LLVM_LIBC_FEATURES_H
+
+#include <__llvm-libc-common.h>
+#include <llvm-libc-macros/features-macros.h>
+
+%%public_api()
+
+#endif // LLVM_LIBC_FEATURES_H
diff --git a/libc/include/llvm-libc-macros/CMakeLists.txt b/libc/include/llvm-libc-macros/CMakeLists.txt
index 8a225889a6f1f87..9c9e6bfd1256453 100644
--- a/libc/include/llvm-libc-macros/CMakeLists.txt
+++ b/libc/include/llvm-libc-macros/CMakeLists.txt
@@ -46,6 +46,12 @@ add_macro_header(
     fcntl-macros.h
 )
 
+add_macro_header(
+  features_macros
+  HDR
+    features-macros.h
+)
+
 add_macro_header(
   fenv_macros
   HDR
diff --git a/libc/include/llvm-libc-macros/features-macros.h b/libc/include/llvm-libc-macros/features-macros.h
new file mode 100644
index 000000000000000..b6941c9547286c0
--- /dev/null
+++ b/libc/include/llvm-libc-macros/features-macros.h
@@ -0,0 +1,14 @@
+//===-- Definition of macros from features.h ----------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __LLVM_LIBC_MACROS_FEATURES_MACROS_H
+#define __LLVM_LIBC_MACROS_FEATURES_MACROS_H
+
+#define __LLVMLIBC__ 1
+
+#endif // __LLVM_LIBC_MACROS_FEATURES_MACROS_H