[libc] Add the <endian.h> header.

[c8ef]

Closes #124631.
ref: https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/endian.h.html

This patch adds the implementation of endian.h, which includes the header itself and three related macros. These macros in the header rely on the compiler preprocessor, similar to how https://github.com/llvm/llvm-project/blob/main/libc/src/__support/endian_internal.h does. Hopefully this will meet the requirements for compiling llvm with llvm-libc.

[llvmbot]

@llvm/pr-subscribers-libc

Author: None (c8ef)

Changes

Closes #124631.
ref: https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/endian.h.html

This patch adds the implementation of endian.h, which includes the header itself and three related macros. These macros in the header rely on the compiler preprocessor, similar to how https://github.com/llvm/llvm-project/blob/main/libc/src/__support/endian_internal.h does. Hopefully this will meet the requirements for compiling llvm with llvm-libc.

---

Full diff: https://github.com/llvm/llvm-project/pull/125168.diff

7 Files Affected:

• (modified) libc/config/linux/aarch64/headers.txt (+1)
• (modified) libc/config/linux/x86_64/headers.txt (+1)
• (modified) libc/include/CMakeLists.txt (+9)
• (added) libc/include/endian.h.def (+17)
• (added) libc/include/endian.yaml (+9)
• (modified) libc/include/llvm-libc-macros/CMakeLists.txt (+6)
• (added) libc/include/llvm-libc-macros/endian-macros.h (+16)

diff --git a/libc/config/linux/aarch64/headers.txt b/libc/config/linux/aarch64/headers.txt
index 05f15a0e4e5cbb..7ff55899805508 100644
--- a/libc/config/linux/aarch64/headers.txt
+++ b/libc/config/linux/aarch64/headers.txt
@@ -4,6 +4,7 @@ set(TARGET_PUBLIC_HEADERS
     libc.include.ctype
     libc.include.dlfcn
     libc.include.elf
+    libc.include.endian
     libc.include.errno
     libc.include.features
     libc.include.fenv
diff --git a/libc/config/linux/x86_64/headers.txt b/libc/config/linux/x86_64/headers.txt
index 8750100302ea7e..fe1fd596960dd3 100644
--- a/libc/config/linux/x86_64/headers.txt
+++ b/libc/config/linux/x86_64/headers.txt
@@ -5,6 +5,7 @@ set(TARGET_PUBLIC_HEADERS
     libc.include.dirent
     libc.include.dlfcn
     libc.include.elf
+    libc.include.endian
     libc.include.errno
     libc.include.fcntl
     libc.include.features
diff --git a/libc/include/CMakeLists.txt b/libc/include/CMakeLists.txt
index e5ceea360d3965..96d715cde9de9d 100644
--- a/libc/include/CMakeLists.txt
+++ b/libc/include/CMakeLists.txt
@@ -73,6 +73,15 @@ add_header_macro(
     .llvm_libc_common_h
 )
 
+add_header_macro(
+  endian
+  ../libc/include/endian.yaml
+  endian.h
+  DEPENDS
+    .llvm-libc-macros.endian_macros
+    .llvm_libc_common_h
+)
+
 add_header_macro(
   features
   ../libc/include/features.yaml
diff --git a/libc/include/endian.h.def b/libc/include/endian.h.def
new file mode 100644
index 00000000000000..8448d93a86acc3
--- /dev/null
+++ b/libc/include/endian.h.def
@@ -0,0 +1,17 @@
+//===-- System V header endian.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_ENDIAN_H
+#define LLVM_LIBC_ENDIAN_H
+
+#include "__llvm-libc-common.h"
+#include "llvm-libc-macros/endian-macros.h"
+
+%%public_api()
+
+#endif // LLVM_LIBC_ENDIAN_H
diff --git a/libc/include/endian.yaml b/libc/include/endian.yaml
new file mode 100644
index 00000000000000..6497f897b63933
--- /dev/null
+++ b/libc/include/endian.yaml
@@ -0,0 +1,9 @@
+header: endian.h
+header_template: endian.h.def
+standards:
+  - POSIX
+macros: []
+types: []
+enums: []
+objects: []
+functions: []
diff --git a/libc/include/llvm-libc-macros/CMakeLists.txt b/libc/include/llvm-libc-macros/CMakeLists.txt
index 9d5d9f65442889..d165ada6612c84 100644
--- a/libc/include/llvm-libc-macros/CMakeLists.txt
+++ b/libc/include/llvm-libc-macros/CMakeLists.txt
@@ -310,6 +310,12 @@ add_macro_header(
     elf-macros.h
 )
 
+add_macro_header(
+  endian_macros
+  HDR
+    endian-macros.h
+)
+
 add_macro_header(
   locale_macros
   HDR
diff --git a/libc/include/llvm-libc-macros/endian-macros.h b/libc/include/llvm-libc-macros/endian-macros.h
new file mode 100644
index 00000000000000..94e1d60f8ff404
--- /dev/null
+++ b/libc/include/llvm-libc-macros/endian-macros.h
@@ -0,0 +1,16 @@
+//===-- Definition of macros from endian.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_ENDIAN_MACROS_H
+#define LLVM_LIBC_MACROS_ENDIAN_MACROS_H
+
+#define LITTLE_ENDIAN __ORDER_LITTLE_ENDIAN__
+#define BIG_ENDIAN __ORDER_BIG_ENDIAN__
+#define BYTE_ORDER __BYTE_ORDER__
+
+#endif // LLVM_LIBC_MACROS_ENDIAN_MACROS_H