diff --git a/libc/cmake/modules/LLVMLibCArchitectures.cmake b/libc/cmake/modules/LLVMLibCArchitectures.cmake
index dacb4db75d337..22ce9f02e2e52 100644
--- a/libc/cmake/modules/LLVMLibCArchitectures.cmake
+++ b/libc/cmake/modules/LLVMLibCArchitectures.cmake
@@ -206,5 +206,12 @@ 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}")
diff --git a/libc/include/llvm-libc-macros/float16-macros.h b/libc/include/llvm-libc-macros/float16-macros.h
index 9a11ecc49307e..229e3e62f2aed 100644
--- a/libc/include/llvm-libc-macros/float16-macros.h
+++ b/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
diff --git a/libc/include/llvm-libc-macros/stdckdint-macros.h b/libc/include/llvm-libc-macros/stdckdint-macros.h
index 694412290bbca..17e4ccdc2d5f8 100644
--- a/libc/include/llvm-libc-macros/stdckdint-macros.h
+++ b/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__
diff --git a/libc/src/__support/CPP/CMakeLists.txt b/libc/src/__support/CPP/CMakeLists.txt
index f2e774f166f66..c1981b827042c 100644
--- a/libc/src/__support/CPP/CMakeLists.txt
+++ b/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
 )
diff --git a/libc/src/__support/CPP/new.cpp b/libc/src/__support/CPP/new.cpp
index 5a40d4a6d3b27..88db8377b2fac 100644
--- a/libc/src/__support/CPP/new.cpp
+++ b/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
 }
diff --git a/libc/src/__support/CPP/new.h b/libc/src/__support/CPP/new.h
index 94a8466a39677..c1b6b95033f84 100644
--- a/libc/src/__support/CPP/new.h
+++ b/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;
   }
diff --git a/libc/src/__support/OSUtil/io.h b/libc/src/__support/OSUtil/io.h
index cb7e748fc6442..80119da77fc02 100644
--- a/libc/src/__support/OSUtil/io.h
+++ b/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"
diff --git a/libc/src/__support/OSUtil/windows/CMakeLists.txt b/libc/src/__support/OSUtil/windows/CMakeLists.txt
new file mode 100644
index 0000000000000..be316d77f5d06
--- /dev/null
+++ b/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
+)
diff --git a/libc/src/__support/OSUtil/windows/exit.cpp b/libc/src/__support/OSUtil/windows/exit.cpp
new file mode 100644
index 0000000000000..369b07b848878
--- /dev/null
+++ b/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
diff --git a/libc/src/__support/OSUtil/windows/io.cpp b/libc/src/__support/OSUtil/windows/io.cpp
new file mode 100644
index 0000000000000..af3d1b9e43976
--- /dev/null
+++ b/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
diff --git a/libc/src/__support/OSUtil/windows/io.h b/libc/src/__support/OSUtil/windows/io.h
new file mode 100644
index 0000000000000..bafc00254a7cf
--- /dev/null
+++ b/libc/src/__support/OSUtil/windows/io.h
@@ -0,0 +1,21 @@
+//===------------- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_OSUTIL_WINDOWS_IO_H
+#define LLVM_LIBC_SRC___SUPPORT_OSUTIL_WINDOWS_IO_H
+
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+void write_to_stderr(cpp::string_view msg);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_OSUTIL_WINDOWS_IO_H
diff --git a/libc/src/__support/macros/properties/types.h b/libc/src/__support/macros/properties/types.h
index 69ddc912238e7..3ede8a6503d77 100644
--- a/libc/src/__support/macros/properties/types.h
+++ b/libc/src/__support/macros/properties/types.h
@@ -35,7 +35,7 @@
 #endif // UINT64_MAX
 
 // int128 / uint128 support
-#if defined(__SIZEOF_INT128__)
+#if defined(__SIZEOF_INT128__) && !defined(LIBC_TARGET_OS_IS_WINDOWS)
 #define LIBC_TYPES_HAS_INT128
 #endif // defined(__SIZEOF_INT128__)
 
diff --git a/libc/test/src/__support/CMakeLists.txt b/libc/test/src/__support/CMakeLists.txt
index 90de520405981..7ad262d5f1f30 100644
--- a/libc/test/src/__support/CMakeLists.txt
+++ b/libc/test/src/__support/CMakeLists.txt
@@ -140,9 +140,14 @@ add_libc_test(
     arg_list_test.cpp
   DEPENDS
     libc.src.__support.arg_list
+    libc.src.__support.macros.properties.os
 )
 
-if(NOT LIBC_TARGET_ARCHITECTURE_IS_NVPTX)
+# TODO: clang-cl generates calls into runtime library functions to
+# handle 128-bit integer arithmetics and conversions which are not yet
+# available on Windows. Re-enable 128-bit integer support on Windows once
+# these functions are ready.
+if(NOT LIBC_TARGET_ARCHITECTURE_IS_NVPTX AND NOT LIBC_TARGET_OS_IS_WINDOWS)
   add_libc_test(
     big_int_test
     SUITE
diff --git a/libc/test/src/__support/FPUtil/CMakeLists.txt b/libc/test/src/__support/FPUtil/CMakeLists.txt
index 22fbd2664b546..1e64e9ba425a5 100644
--- a/libc/test/src/__support/FPUtil/CMakeLists.txt
+++ b/libc/test/src/__support/FPUtil/CMakeLists.txt
@@ -25,6 +25,7 @@ add_libc_test(
     libc.src.__support.FPUtil.fp_bits
     libc.src.__support.FPUtil.fpbits_str
     libc.src.__support.integer_literals
+    libc.src.__support.macros.properties.types
     libc.src.__support.sign
 )
 
diff --git a/libc/test/src/__support/FPUtil/fpbits_test.cpp b/libc/test/src/__support/FPUtil/fpbits_test.cpp
index 99acc03010344..df50d8546f34f 100644
--- a/libc/test/src/__support/FPUtil/fpbits_test.cpp
+++ b/libc/test/src/__support/FPUtil/fpbits_test.cpp
@@ -9,6 +9,7 @@
 #include "src/__support/FPUtil/FPBits.h"
 #include "src/__support/FPUtil/fpbits_str.h"
 #include "src/__support/integer_literals.h"
+#include "src/__support/macros/properties/types.h"
 #include "src/__support/sign.h" // Sign
 #include "test/UnitTest/Test.h"
 
@@ -425,13 +426,10 @@ TEST(LlvmLibcFPBitsTest, DoubleType) {
   EXPECT_EQ(quiet_nan.is_quiet_nan(), true);
 }
 
-#ifdef LIBC_TARGET_ARCH_IS_X86
+#ifdef LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80
 TEST(LlvmLibcFPBitsTest, X86LongDoubleType) {
   using LongDoubleBits = FPBits<long double>;
 
-  if constexpr (sizeof(long double) == sizeof(double))
-    return; // The tests for the "double" type cover for this case.
-
   EXPECT_STREQ(LIBC_NAMESPACE::str(LongDoubleBits::inf(Sign::POS)).c_str(),
                "(+Infinity)");
   EXPECT_STREQ(LIBC_NAMESPACE::str(LongDoubleBits::inf(Sign::NEG)).c_str(),
diff --git a/libc/test/src/__support/arg_list_test.cpp b/libc/test/src/__support/arg_list_test.cpp
index 4f229e2bfe694..79a715e910687 100644
--- a/libc/test/src/__support/arg_list_test.cpp
+++ b/libc/test/src/__support/arg_list_test.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/__support/arg_list.h"
+#include "src/__support/macros/properties/os.h"
 
 #include "test/UnitTest/Test.h"
 
@@ -120,7 +121,7 @@ TEST(LlvmLibcArgListTest, TestStructTypes) {
 }
 
 // Test vector extensions from clang.
-#if __has_attribute(ext_vector_type)
+#if !defined(LIBC_TARGET_OS_IS_WINDOWS) && __has_attribute(ext_vector_type)
 
 using int1 = int __attribute__((ext_vector_type(1)));
 using int2 = int __attribute__((ext_vector_type(2)));
diff --git a/libc/test/src/fenv/CMakeLists.txt b/libc/test/src/fenv/CMakeLists.txt
index b776f9a0706e8..d79b4a49a5e4f 100644
--- a/libc/test/src/fenv/CMakeLists.txt
+++ b/libc/test/src/fenv/CMakeLists.txt
@@ -41,6 +41,7 @@ add_libc_unittest(
     libc.src.fenv.fesetenv
     libc.src.fenv.fesetround
     libc.src.__support.FPUtil.fenv_impl
+    libc.src.__support.macros.properties.os
   LINK_LIBRARIES
     LibcFPTestHelpers
 )
diff --git a/libc/test/src/fenv/getenv_and_setenv_test.cpp b/libc/test/src/fenv/getenv_and_setenv_test.cpp
index 8fc2787ecb5b1..fa4ef662222af 100644
--- a/libc/test/src/fenv/getenv_and_setenv_test.cpp
+++ b/libc/test/src/fenv/getenv_and_setenv_test.cpp
@@ -13,6 +13,7 @@
 #include "src/fenv/fesetround.h"
 
 #include "src/__support/FPUtil/FEnvImpl.h"
+#include "src/__support/macros/properties/os.h"
 #include "test/UnitTest/FEnvSafeTest.h"
 #include "test/UnitTest/Test.h"
 
@@ -20,6 +21,7 @@
 
 using LlvmLibcFEnvTest = LIBC_NAMESPACE::testing::FEnvSafeTest;
 
+#ifndef LIBC_TARGET_OS_IS_WINDOWS
 TEST_F(LlvmLibcFEnvTest, GetEnvAndSetEnv) {
   // We will disable all exceptions to prevent invocation of the exception
   // handler.
@@ -71,8 +73,9 @@ TEST_F(LlvmLibcFEnvTest, Set_FE_DFL_ENV) {
   int rm = LIBC_NAMESPACE::fegetround();
   EXPECT_EQ(rm, FE_TONEAREST);
 }
+#endif
 
-#ifdef _WIN32
+#ifdef LIBC_TARGET_OS_IS_WINDOWS
 TEST_F(LlvmLibcFEnvTest, Windows_Set_Get_Test) {
   // If a valid fenv_t is written, then reading it back out should be identical.
   fenv_t setEnv = {0x7e00053e, 0x0f00000f};
diff --git a/libc/test/src/math/smoke/AddTest.h b/libc/test/src/math/smoke/AddTest.h
index 0b7e395a22d4c..88c2067ca1474 100644
--- a/libc/test/src/math/smoke/AddTest.h
+++ b/libc/test/src/math/smoke/AddTest.h
@@ -12,6 +12,7 @@
 #include "hdr/errno_macros.h"
 #include "hdr/fenv_macros.h"
 #include "src/__support/FPUtil/BasicOperations.h"
+#include "src/__support/macros/properties/os.h"
 #include "test/UnitTest/FEnvSafeTest.h"
 #include "test/UnitTest/FPMatcher.h"
 #include "test/UnitTest/Test.h"
@@ -53,6 +54,7 @@ class AddTest : public LIBC_NAMESPACE::testing::FEnvSafeTest {
   }
 
   void test_range_errors(AddFunc func) {
+#ifndef LIBC_TARGET_OS_IS_WINDOWS
     using namespace LIBC_NAMESPACE::fputil::testing;
 
     if (ForceRoundingMode r(RoundingMode::Nearest); r.success) {
@@ -121,6 +123,7 @@ class AddTest : public LIBC_NAMESPACE::testing::FEnvSafeTest {
           FE_UNDERFLOW | FE_INEXACT);
       EXPECT_MATH_ERRNO(ERANGE);
     }
+#endif
   }
 
   void test_inexact_results(AddFunc func) {
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
index 7271e933b9311..9b67a83d35663 100644
--- a/libc/test/src/math/smoke/CMakeLists.txt
+++ b/libc/test/src/math/smoke/CMakeLists.txt
@@ -153,6 +153,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.fadd
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -168,6 +169,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.faddl
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -183,6 +185,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.faddf128
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -424,6 +427,7 @@ add_fp_unittest(
     libc.src.errno.errno
     libc.hdr.fenv_macros
     libc.src.math.dsubl
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -438,6 +442,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.dsubf128
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -4169,6 +4174,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.f16add
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -4183,6 +4189,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.f16addf
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -4197,6 +4204,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.f16addl
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -4211,6 +4219,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.f16addf128
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -4225,6 +4234,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.f16sub
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -4239,6 +4249,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.f16subf
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -4253,6 +4264,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.f16subl
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -4267,6 +4279,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.f16subf128
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -4548,6 +4561,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.fsub
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -4562,6 +4576,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.fsubl
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -4576,6 +4591,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.fsubf128
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -4749,6 +4765,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.daddl
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
@@ -4763,6 +4780,7 @@ add_fp_unittest(
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
     libc.src.math.daddf128
+    libc.src.__support.macros.properties.os
 )
 
 add_fp_unittest(
diff --git a/libc/test/src/math/smoke/SubTest.h b/libc/test/src/math/smoke/SubTest.h
index 9ee4220b38208..99c4b6c760af7 100644
--- a/libc/test/src/math/smoke/SubTest.h
+++ b/libc/test/src/math/smoke/SubTest.h
@@ -11,6 +11,7 @@
 
 #include "hdr/errno_macros.h"
 #include "hdr/fenv_macros.h"
+#include "src/__support/macros/properties/os.h"
 #include "test/UnitTest/FEnvSafeTest.h"
 #include "test/UnitTest/FPMatcher.h"
 #include "test/UnitTest/Test.h"
@@ -52,6 +53,7 @@ class SubTest : public LIBC_NAMESPACE::testing::FEnvSafeTest {
   }
 
   void test_range_errors(SubFunc func) {
+#ifndef LIBC_TARGET_OS_IS_WINDOWS
     using namespace LIBC_NAMESPACE::fputil::testing;
 
     if (ForceRoundingMode r(RoundingMode::Nearest); r.success) {
@@ -123,6 +125,7 @@ class SubTest : public LIBC_NAMESPACE::testing::FEnvSafeTest {
                                   FE_UNDERFLOW | FE_INEXACT);
       EXPECT_MATH_ERRNO(ERANGE);
     }
+#endif
   }
 
   void test_inexact_results(SubFunc func) {
diff --git a/libc/test/src/string/memory_utils/CMakeLists.txt b/libc/test/src/string/memory_utils/CMakeLists.txt
index a0dddd2f97b58..8374be4a1d01a 100644
--- a/libc/test/src/string/memory_utils/CMakeLists.txt
+++ b/libc/test/src/string/memory_utils/CMakeLists.txt
@@ -12,6 +12,7 @@ add_libc_test(
     libc.src.__support.CPP.array
     libc.src.__support.CPP.cstddef
     libc.src.__support.CPP.span
+    libc.src.__support.macros.properties.os
     libc.src.__support.macros.properties.types
     libc.src.__support.macros.sanitizer
     libc.src.string.memory_utils.memory_utils
diff --git a/libc/test/src/string/memory_utils/op_tests.cpp b/libc/test/src/string/memory_utils/op_tests.cpp
index 978561f31a296..c6197d1afa266 100644
--- a/libc/test/src/string/memory_utils/op_tests.cpp
+++ b/libc/test/src/string/memory_utils/op_tests.cpp
@@ -8,6 +8,7 @@
 
 #include "memory_check_utils.h"
 #include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/os.h"
 #include "src/__support/macros/properties/types.h" // LIBC_TYPES_HAS_INT64
 #include "src/string/memory_utils/op_aarch64.h"
 #include "src/string/memory_utils/op_builtin.h"
@@ -294,7 +295,7 @@ TYPED_TEST(LlvmLibcOpTest, Bcmp, BcmpImplementations) {
 #endif // LIBC_TARGET_ARCH_IS_X86_64
 
 using MemcmpImplementations = testing::TypeList<
-#ifdef LIBC_TARGET_ARCH_IS_X86_64
+#if defined(LIBC_TARGET_ARCH_IS_X86_64) && !defined(LIBC_TARGET_OS_IS_WINDOWS)
 #ifdef __SSE2__
     generic::Memcmp<__m128i>, //
 #endif