[libc] Add osutils for Windows and make libc and its tests build on Windows target (#104676)

This PR first adds osutils for Windows, and changes some libc code to
make libc and its tests build on the Windows target. It then temporarily
disables some libc tests that are currently problematic on Windows.

Specifically, the changes besides the addition of osutils include:

- Macro `LIBC_TYPES_HAS_FLOAT16` is disabled on Windows. `clang-cl`
generates calls to functions in `compiler-rt` to handle float16
arithmetic and these functions are currently not linked in on Windows.
- Macro `LIBC_TYPES_HAS_INT128` is disabled on Windows.
- The invocation to `::aligned_malloc` is changed to an invocation to
`::_aligned_malloc`.
- The following unit tests are temporarily disabled because they
currently fail on Windows:
  - `test.src.__support.big_int_test`
  - `test.src.__support.arg_list_test`
  - `test.src.fenv.getenv_and_setenv_test`
- Tests involving `__m128i`, `__m256i`, and `__m512i` in
`test.src.string.memory_utils.op_tests.cpp`
- `test_range_errors` in `libc/test/src/math/smoke/AddTest.h` and
`libc/test/src/math/smoke/SubTest.h`

Author: Lancern

libc/cmake/modules/LLVMLibCArchitectures.cmake

@@ -206,6 +206,13 @@ if(explicit_target_triple AND
   endif()
 endif()
 
+
+# Windows does not support full mode build.
+if (LIBC_TARGET_OS_IS_WINDOWS AND LLVM_LIBC_FULL_BUILD)
+  message(FATAL_ERROR "Windows does not support full mode build.")
+endif ()
+
+
 message(STATUS
         "Building libc for ${LIBC_TARGET_ARCHITECTURE} on ${LIBC_TARGET_OS} with
         LIBC_COMPILE_OPTIONS_DEFAULT: ${LIBC_COMPILE_OPTIONS_DEFAULT}")

libc/include/llvm-libc-macros/float16-macros.h

@@ -13,7 +13,8 @@
 
 #if defined(__FLT16_MANT_DIG__) &&                                             \
     (!defined(__GNUC__) || __GNUC__ >= 13 || defined(__clang__)) &&            \
-    !defined(__arm__) && !defined(_M_ARM) && !defined(__riscv)
+    !defined(__arm__) && !defined(_M_ARM) && !defined(__riscv) &&              \
+    !defined(_WIN32)
 #define LIBC_TYPES_HAS_FLOAT16
 
 // TODO: This would no longer be required if HdrGen let us guard function

libc/include/llvm-libc-macros/stdckdint-macros.h

@@ -10,8 +10,10 @@
 #define LLVM_LIBC_MACROS_STDCKDINT_MACROS_H
 
 // We need to use __builtin_*_overflow from GCC/Clang to implement the overflow
-// macros. Check __GNUC__ for availability of such builtins.
-#ifdef __GNUC__
+// macros. Check __GNUC__ or __clang__ for availability of such builtins.
+// Note that clang-cl defines __clang__ only and does not define __GNUC__ so we
+// have to check for both.
+#if defined(__GNUC__) || defined(__clang__)
 // clang/gcc overlay may provides similar macros, we need to avoid redefining
 // them.
 #ifndef __STDC_VERSION_STDCKDINT_H__

libc/src/__support/CPP/CMakeLists.txt

@@ -199,4 +199,5 @@ add_object_library(
   DEPENDS
     libc.include.stdlib
     libc.src.__support.common
+    libc.src.__support.macros.properties.os
 )

libc/src/__support/CPP/new.cpp

@@ -16,15 +16,29 @@ void operator delete(void *mem, std::align_val_t) noexcept { ::free(mem); }
 void operator delete(void *mem, size_t) noexcept { ::free(mem); }
 
 void operator delete(void *mem, size_t, std::align_val_t) noexcept {
+#ifdef LIBC_TARGET_OS_IS_WINDOWS
+  ::_aligned_free(mem);
+#else
   ::free(mem);
+#endif
 }
 
 void operator delete[](void *mem) noexcept { ::free(mem); }
 
-void operator delete[](void *mem, std::align_val_t) noexcept { ::free(mem); }
+void operator delete[](void *mem, std::align_val_t) noexcept {
+#ifdef LIBC_TARGET_OS_IS_WINDOWS
+  ::_aligned_free(mem);
+#else
+  ::free(mem);
+#endif
+}
 
 void operator delete[](void *mem, size_t) noexcept { ::free(mem); }
 
 void operator delete[](void *mem, size_t, std::align_val_t) noexcept {
+#ifdef LIBC_TARGET_OS_IS_WINDOWS
+  ::_aligned_free(mem);
+#else
   ::free(mem);
+#endif
 }

libc/src/__support/CPP/new.h

@@ -11,6 +11,7 @@
 
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/os.h"
 
 #include <stddef.h> // For size_t
 #include <stdlib.h> // For malloc, free etc.
@@ -47,7 +48,15 @@ class AllocChecker {
 
   LIBC_INLINE static void *aligned_alloc(size_t s, std::align_val_t align,
                                          AllocChecker &ac) {
+#ifdef LIBC_TARGET_OS_IS_WINDOWS
+    // std::aligned_alloc is not available on Windows because std::free on
+    // Windows cannot deallocate any over-aligned memory. Microsoft provides an
+    // alternative for std::aligned_alloc named _aligned_malloc, but it must be
+    // paired with _aligned_free instead of std::free.
+    void *mem = ::_aligned_malloc(static_cast<size_t>(align), s);
+#else
     void *mem = ::aligned_alloc(static_cast<size_t>(align), s);
+#endif
     ac = (mem != nullptr);
     return mem;
   }

libc/src/__support/OSUtil/io.h

@@ -19,6 +19,8 @@
 #include "linux/io.h"
 #elif defined(__Fuchsia__)
 #include "fuchsia/io.h"
+#elif defined(_WIN32)
+#include "windows/io.h"
 #elif defined(__ELF__)
 // TODO: Ideally we would have LIBC_TARGET_OS_IS_BAREMETAL.
 #include "baremetal/io.h"

libc/src/__support/OSUtil/windows/CMakeLists.txt

@@ -0,0 +1,10 @@
+add_object_library(
+  windows_util
+  SRCS
+    exit.cpp
+    io.cpp
+  HDRS
+    io.h
+  DEPENDS
+    libc.src.__support.macros.config
+)

libc/src/__support/OSUtil/windows/exit.cpp

@@ -0,0 +1,23 @@
+//===-- Windows implementation of an exit function ------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/macros/config.h"
+
+// On Windows we cannot make direct syscalls since Microsoft changes system call
+// IDs periodically. We must rely on functions exported from ntdll.dll or
+// kernel32.dll to invoke system service procedures.
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+
+namespace LIBC_NAMESPACE_DECL {
+namespace internal {
+
+[[noreturn]] void exit(int status) { ::ExitProcess(status); }
+
+} // namespace internal
+} // namespace LIBC_NAMESPACE_DECL

libc/src/__support/OSUtil/windows/io.cpp

@@ -0,0 +1,25 @@
+//===------------- Windows implementation of IO utils -----------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "io.h"
+#include "src/__support/macros/config.h"
+
+// On Windows we cannot make direct syscalls since Microsoft changes system call
+// IDs periodically. We must rely on functions exported from ntdll.dll or
+// kernel32.dll to invoke system service procedures.
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+
+namespace LIBC_NAMESPACE_DECL {
+
+void write_to_stderr(cpp::string_view msg) {
+  ::HANDLE stream = ::GetStdHandle(STD_ERROR_HANDLE);
+  ::WriteFile(stream, msg.data(), msg.size(), nullptr, nullptr);
+}
+
+} // namespace LIBC_NAMESPACE_DECL