[libc] Move libc_errno.h to libc/src/__support and make LIBC_ERRNO_MODE_SYSTEM to be header-only.

libc/cmake/modules/LLVMLibCCompileOptionRules.cmake

@@ -106,6 +106,10 @@ function(_get_compile_options_from_config output_var)
     list(APPEND config_options "-DLIBC_MATH=${LIBC_CONF_MATH_OPTIMIZATIONS}")
   endif()
 
+  if(LIBC_CONF_ERRNO_MODE)
+    set(APPEND config_options "-DLIBC_ERRNO_MODE=${LIBC_CONF_ERRNO_MODE}")
+  endif()
+
   set(${output_var} ${config_options} PARENT_SCOPE)
 endfunction(_get_compile_options_from_config)
 

libc/config/config.json

@@ -2,7 +2,7 @@
   "errno": {
     "LIBC_CONF_ERRNO_MODE": {
       "value": "LIBC_ERRNO_MODE_DEFAULT",
-      "doc": "The implementation used for errno, acceptable values are LIBC_ERRNO_MODE_DEFAULT, LIBC_ERRNO_MODE_UNDEFINED, LIBC_ERRNO_MODE_THREAD_LOCAL, LIBC_ERRNO_MODE_SHARED, LIBC_ERRNO_MODE_EXTERNAL, and LIBC_ERRNO_MODE_SYSTEM."
+      "doc": "The implementation used for errno, acceptable values are LIBC_ERRNO_MODE_DEFAULT, LIBC_ERRNO_MODE_UNDEFINED, LIBC_ERRNO_MODE_THREAD_LOCAL, LIBC_ERRNO_MODE_SHARED, LIBC_ERRNO_MODE_EXTERNAL, LIBC_ERRNO_MODE_SYSTEM, and LIBC_ERRNO_MODE_SYSTEM_INLINE."
     }
   },
   "printf": {

libc/docs/dev/code_style.rst

@@ -101,7 +101,7 @@ test infrastructure itself can be affected. To avoid perturbing the unit test
 infrastructure around the setting of ``errno``, the following rules are to be
 followed:
 
-#. A special macro named ``libc_errno`` defined in ``src/errno/libc_errno.h``
+#. A special macro named ``libc_errno`` defined in ``src/__support/libc_errno.h``
    should be used when setting ``errno`` from libc runtime code. For example,
    code to set ``errno`` to ``EINVAL`` should be:
 
@@ -117,7 +117,7 @@ followed:
    `ErrorOr <https://github.com/llvm/llvm-project/blob/main/libc/src/__support/error_or.h>`_
    to return error values.
 
-#. The header file ``src/errno/libc_errno.h`` is shipped as part of the target
+#. The header file ``src/__support/libc_errno.h`` is shipped as part of the target
    corresponding to the ``errno`` entrypoint ``libc.src.errno.errno``. We do
    not in general allow dependencies between entrypoints. However, the ``errno``
    entrypoint is the only exceptional entrypoint on which other entrypoints

libc/shared/fp_bits.h

@@ -9,6 +9,7 @@
 #ifndef LLVM_LIBC_SHARED_FP_BITS_H
 #define LLVM_LIBC_SHARED_FP_BITS_H
 
+#include "libc_common.h"
 #include "src/__support/FPUtil/FPBits.h"
 
 namespace LIBC_NAMESPACE_DECL {

libc/shared/libc_common.h

@@ -0,0 +1,26 @@
+//===-- Common defines for sharing LLVM libc with LLVM projects -*- C++ -*-===//
+//
+// 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_SHARED_LIBC_COMMON_H
+#define LLVM_LIBC_SHARED_LIBC_COMMON_H
+
+// Use system errno.
+#ifdef LIBC_ERRNO_MODE
+#if LIBC_ERRNO_MODE != LIBC_ERRNO_MODE_SYSTEM_INLINE
+#error                                                                         \
+    "LIBC_ERRNO_MODE was set to something different from LIBC_ERRNO_MODE_SYSTEM_INLINE."
+#endif // LIBC_ERRNO_MODE != LIBC_ERRNO_MODE_SYSTEM_INLINE
+#else
+#define LIBC_ERRNO_MODE LIBC_ERRNO_MODE_SYSTEM_INLINE
+#endif // LIBC_ERRNO_MODE
+
+#ifndef LIBC_NAMESPACE
+#define LIBC_NAMESPACE __llvm_libc
+#endif // LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SHARED_LIBC_COMMON_H

libc/shared/rpc_server.h

@@ -9,6 +9,7 @@
 #ifndef LLVM_LIBC_SHARED_RPC_SERVER_H
 #define LLVM_LIBC_SHARED_RPC_SERVER_H
 
+#include "libc_common.h"
 #include "src/__support/RPC/rpc_server.h"
 
 namespace LIBC_NAMESPACE_DECL {

libc/shared/str_to_float.h

@@ -9,6 +9,7 @@
 #ifndef LLVM_LIBC_SHARED_STR_TO_FLOAT_H
 #define LLVM_LIBC_SHARED_STR_TO_FLOAT_H
 
+#include "libc_common.h"
 #include "src/__support/str_to_float.h"
 
 namespace LIBC_NAMESPACE_DECL {

libc/shared/str_to_integer.h

@@ -9,6 +9,7 @@
 #ifndef LLVM_LIBC_SHARED_STR_TO_INTEGER_H
 #define LLVM_LIBC_SHARED_STR_TO_INTEGER_H
 
+#include "libc_common.h"
 #include "src/__support/str_to_integer.h"
 
 namespace LIBC_NAMESPACE_DECL {

libc/src/__support/CMakeLists.txt

@@ -1,6 +1,15 @@
 add_subdirectory(CPP)
 add_subdirectory(macros)
 
+add_header_library(
+  libc_errno
+  HDRS
+    libc_errno.h
+  DEPENDS
+    libc.hdr.errno_macros
+    libc.src.__support.macros.config
+)
+
 add_header_library(
   block
   HDRS

libc/src/__support/FPUtil/FEnvImpl.h

@@ -12,10 +12,10 @@
 #include "hdr/fenv_macros.h"
 #include "hdr/math_macros.h"
 #include "hdr/types/fenv_t.h"
+#include "src/__support/libc_errno.h"
 #include "src/__support/macros/attributes.h" // LIBC_INLINE
 #include "src/__support/macros/config.h"
 #include "src/__support/macros/properties/architectures.h"
-#include "src/errno/libc_errno.h"
 
 #if defined(LIBC_TARGET_ARCH_IS_AARCH64) && defined(__ARM_FP)
 #if defined(__APPLE__)

libc/src/__support/File/dir.cpp

@@ -11,8 +11,8 @@
 #include "src/__support/CPP/mutex.h" // lock_guard
 #include "src/__support/CPP/new.h"
 #include "src/__support/error_or.h"
+#include "src/__support/libc_errno.h" // For error macros
 #include "src/__support/macros/config.h"
-#include "src/errno/libc_errno.h" // For error macros
 
 namespace LIBC_NAMESPACE_DECL {
 

libc/src/__support/File/file.cpp

@@ -13,8 +13,8 @@
 #include "hdr/types/off_t.h"
 #include "src/__support/CPP/new.h"
 #include "src/__support/CPP/span.h"
+#include "src/__support/libc_errno.h" // For error macros
 #include "src/__support/macros/config.h"
-#include "src/errno/libc_errno.h" // For error macros
 
 namespace LIBC_NAMESPACE_DECL {
 

libc/src/__support/File/linux/file.cpp

@@ -15,8 +15,8 @@
 #include "src/__support/File/linux/lseekImpl.h"
 #include "src/__support/OSUtil/fcntl.h"
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/libc_errno.h"     // For error macros
 #include "src/__support/macros/config.h"
-#include "src/errno/libc_errno.h" // For error macros
 
 #include "hdr/fcntl_macros.h" // For mode_t and other flags to the open syscall
 #include <sys/stat.h>    // For S_IS*, S_IF*, and S_IR* flags.

libc/src/__support/File/linux/lseekImpl.h

@@ -13,8 +13,8 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 #include "src/__support/error_or.h"
+#include "src/__support/libc_errno.h"
 #include "src/__support/macros/config.h"
-#include "src/errno/libc_errno.h"
 
 #include <stdint.h>      // For uint64_t.
 #include <sys/syscall.h> // For syscall numbers.

libc/src/__support/HashTable/randomness.h

@@ -14,7 +14,7 @@
 #include "src/__support/macros/attributes.h"
 #include "src/__support/macros/config.h"
 #if defined(LIBC_HASHTABLE_USE_GETRANDOM)
-#include "src/errno/libc_errno.h"
+#include "src/__support/libc_errno.h"
 #include "src/sys/random/getrandom.h"
 #endif
 

libc/src/__support/OSUtil/linux/fcntl.cpp

@@ -15,8 +15,8 @@
 #include "hdr/types/struct_flock64.h"
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
 #include "src/__support/macros/config.h"
-#include "src/errno/libc_errno.h"
 
 #include <stdarg.h>
 #include <sys/syscall.h> // For syscall numbers.

libc/src/__support/OSUtil/linux/vdso.cpp

@@ -11,9 +11,9 @@
 #include "src/__support/CPP/array.h"
 #include "src/__support/CPP/optional.h"
 #include "src/__support/CPP/string_view.h"
+#include "src/__support/libc_errno.h"
 #include "src/__support/threads/callonce.h"
 #include "src/__support/threads/linux/futex_word.h"
-#include "src/errno/libc_errno.h"
 #include "src/sys/auxv/getauxval.h"
 #include <linux/auxvec.h>
 

libc/src/__support/StringUtil/tables/linux_extension_errors.h

@@ -10,8 +10,8 @@
 #define LLVM_LIBC_SRC___SUPPORT_STRINGUTIL_TABLES_LINUX_EXTENSION_ERRORS_H
 
 #include "src/__support/StringUtil/message_mapper.h"
+#include "src/__support/libc_errno.h"
 #include "src/__support/macros/config.h"
-#include "src/errno/libc_errno.h"
 
 namespace LIBC_NAMESPACE_DECL {
 

libc/src/__support/libc_errno.h

@@ -0,0 +1,108 @@
+//===-- Implementation header for libc_errno --------------------*- C++ -*-===//
+//
+// 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_SRC___SUPPORT_LIBC_ERRNO_H
+#define LLVM_LIBC_SRC___SUPPORT_LIBC_ERRNO_H
+
+// This header is to be consumed by internal implementations, in which all of
+// them should refer to `libc_errno` instead of using `errno` directly from
+// <errno.h> header.
+
+// Unit and hermetic tests should:
+// - #include "src/__support/libc_errno.h"
+// - NOT #include <errno.h>
+// - Only use `libc_errno` in the code
+// - Depend on libc.src.errno.errno
+
+// Integration tests should:
+// - NOT #include "src/__support/libc_errno.h"
+// - #include <errno.h>
+// - Use regular `errno` in the code
+// - Still depend on libc.src.errno.errno
+
+// libc uses a fallback default value, either system or thread local.
+#define LIBC_ERRNO_MODE_DEFAULT 0
+// libc never stores a value; `errno` macro uses get link-time failure.
+#define LIBC_ERRNO_MODE_UNDEFINED 1
+// libc maintains per-thread state (requires C++ `thread_local` support).
+#define LIBC_ERRNO_MODE_THREAD_LOCAL 2
+// libc maintains shared state used by all threads, contrary to standard C
+// semantics unless always single-threaded; nothing prevents data races.
+#define LIBC_ERRNO_MODE_SHARED 3
+// libc doesn't maintain any internal state, instead the embedder must define
+// `int *__llvm_libc_errno(void);` C function.
+#define LIBC_ERRNO_MODE_EXTERNAL 4
+// libc uses system `<errno.h>` `errno` macro directly in the overlay mode; in
+// fullbuild mode, effectively the same as `LIBC_ERRNO_MODE_EXTERNAL`.
+// In this mode, the public C++ symbol `LIBC_NAMESPACE::libc_errno ` is still
+// exported and get redirected to the system `errno` inside its implementation.
+
+// TODO: Investigate deprecating LIBC_ERRNO_MODE_SYSTEM in favor of
+//       LIBC_ERRNO_MODE_SYSTEM_INLINE.
+//       https://github.com/llvm/llvm-project/issues/143454
+#define LIBC_ERRNO_MODE_SYSTEM 5
+// In this mode, the libc_errno is simply a macro resolved to `errno` from the
+// system header <errno.h>.  There is no need to link against the
+// `libc.src.errno.errno` object.
+#define LIBC_ERRNO_MODE_SYSTEM_INLINE 6
+
+#if !defined(LIBC_ERRNO_MODE) || LIBC_ERRNO_MODE == LIBC_ERRNO_MODE_DEFAULT
+#undef LIBC_ERRNO_MODE
+#if defined(LIBC_FULL_BUILD) || !defined(LIBC_COPT_PUBLIC_PACKAGING)
+#define LIBC_ERRNO_MODE LIBC_ERRNO_MODE_THREAD_LOCAL
+#else
+#define LIBC_ERRNO_MODE LIBC_ERRNO_MODE_SYSTEM
+#endif
+#endif // LIBC_ERRNO_MODE
+
+#if LIBC_ERRNO_MODE != LIBC_ERRNO_MODE_DEFAULT &&                              \
+    LIBC_ERRNO_MODE != LIBC_ERRNO_MODE_UNDEFINED &&                            \
+    LIBC_ERRNO_MODE != LIBC_ERRNO_MODE_THREAD_LOCAL &&                         \
+    LIBC_ERRNO_MODE != LIBC_ERRNO_MODE_SHARED &&                               \
+    LIBC_ERRNO_MODE != LIBC_ERRNO_MODE_EXTERNAL &&                             \
+    LIBC_ERRNO_MODE != LIBC_ERRNO_MODE_SYSTEM &&                               \
+    LIBC_ERRNO_MODE != LIBC_ERRNO_MODE_SYSTEM_INLINE
+#error LIBC_ERRNO_MODE must be one of the following values: \
+LIBC_ERRNO_MODE_DEFAULT, \
+LIBC_ERRNO_MODE_UNDEFINED, \
+LIBC_ERRNO_MODE_THREAD_LOCAL, \
+LIBC_ERRNO_MODE_SHARED, \
+LIBC_ERRNO_MODE_EXTERNAL, \
+LIBC_ERRNO_MODE_SYSTEM, \
+LIBC_ERRNO_MODE_SYSTEM_INLINE.
+#endif
+
+#if LIBC_ERRNO_MODE == LIBC_ERRNO_MODE_SYSTEM_INLINE
+
+#include <errno.h>
+
+#define libc_errno errno
+
+#else // !LIBC_ERRNO_MODE_SYSTEM_INLINE
+
+#include "hdr/errno_macros.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+extern "C" int *__llvm_libc_errno() noexcept;
+
+struct Errno {
+  void operator=(int);
+  operator int();
+};
+
+extern Errno libc_errno;
+
+} // namespace LIBC_NAMESPACE_DECL
+
+using LIBC_NAMESPACE::libc_errno;
+
+#endif // LIBC_ERRNO_MODE_SYSTEM_INLINE
+
+#endif // LLVM_LIBC_SRC___SUPPORT_LIBC_ERRNO_H

libc/src/__support/threads/linux/thread.cpp

@@ -14,9 +14,9 @@
 #include "src/__support/OSUtil/syscall.h" // For syscall functions.
 #include "src/__support/common.h"
 #include "src/__support/error_or.h"
+#include "src/__support/libc_errno.h" // For error macros
 #include "src/__support/macros/config.h"
 #include "src/__support/threads/linux/futex_utils.h" // For FutexWordType
-#include "src/errno/libc_errno.h"                    // For error macros
 
 #ifdef LIBC_TARGET_ARCH_IS_AARCH64
 #include <arm_acle.h>

libc/src/dirent/closedir.cpp

@@ -10,8 +10,8 @@
 
 #include "src/__support/File/dir.h"
 #include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
 #include "src/__support/macros/config.h"
-#include "src/errno/libc_errno.h"
 
 #include <dirent.h>
 

libc/src/dirent/opendir.cpp

@@ -10,8 +10,8 @@
 
 #include "src/__support/File/dir.h"
 #include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
 #include "src/__support/macros/config.h"
-#include "src/errno/libc_errno.h"
 
 #include <dirent.h>
 

libc/src/dirent/readdir.cpp

@@ -10,8 +10,8 @@
 
 #include "src/__support/File/dir.h"
 #include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
 #include "src/__support/macros/config.h"
-#include "src/errno/libc_errno.h"
 
 #include <dirent.h>
 

libc/src/errno/CMakeLists.txt

@@ -1,28 +1,16 @@
 # If we are in full build mode, we will provide the errno definition ourselves,
 # and if we are in overlay mode, we will just re-use the system's errno.
-# We are passing LIBC_FULL_BUILD flag in full build mode so that the
-# implementation of libc_errno will know if we are in full build mode or not.
-
-# TODO: Move LIBC_FULL_BUILD flag to _get_common_compile_options.
-set(full_build_flag "")
-if(LLVM_LIBC_FULL_BUILD)
-  set(full_build_flag "-DLIBC_FULL_BUILD")
-endif()
-
-if(LIBC_CONF_ERRNO_MODE)
-  set(errno_config_copts "-DLIBC_ERRNO_MODE=${LIBC_CONF_ERRNO_MODE}")
-endif()
 
 add_entrypoint_object(
   errno
   SRCS
     libc_errno.cpp
   HDRS
-    libc_errno.h     # Include this
-  COMPILE_OPTIONS
-    ${full_build_flag}
-    ${errno_config_copts}
+    ../__support/libc_errno.h
   DEPENDS
     libc.hdr.errno_macros
     libc.src.__support.common
+    libc.src.__support.libc_errno
+    libc.src.__support.macros.attributes
+    libc.src.__support.macros.config
 )