diff --git a/libc/src/CMakeLists.txt b/libc/src/CMakeLists.txt
--- a/libc/src/CMakeLists.txt
+++ b/libc/src/CMakeLists.txt
@@ -9,7 +9,7 @@
 add_subdirectory(stdlib)
 add_subdirectory(stdio)
 
-if(${LIBC_TARGET_OS} STREQUAL "linux")
+if((${LIBC_TARGET_OS} STREQUAL "linux") OR (${LIBC_TARGET_OS} STREQUAL "windows"))
   add_subdirectory(dirent)
   add_subdirectory(fcntl)
   add_subdirectory(pthread)
diff --git a/libc/src/__support/FPUtil/x86_64/FEnvImpl.h b/libc/src/__support/FPUtil/x86_64/FEnvImpl.h
--- a/libc/src/__support/FPUtil/x86_64/FEnvImpl.h
+++ b/libc/src/__support/FPUtil/x86_64/FEnvImpl.h
@@ -54,8 +54,8 @@
   // support compiling against headers provided by such libcs.
   static constexpr uint16_t DENORMAL = 0x2;
   static constexpr uint16_t DIV_BY_ZERO = 0x4;
-  static constexpr uint16_t OVERFLOW = 0x8;
-  static constexpr uint16_t UNDERFLOW = 0x10;
+  static constexpr uint16_t OVERFLOW_F = 0x8;
+  static constexpr uint16_t UNDERFLOW_F = 0x10;
   static constexpr uint16_t INEXACT = 0x20;
 };
 
@@ -76,8 +76,8 @@
          (excepts & __FE_DENORM ? ExceptionFlags::DENORMAL : 0) |
 #endif // __FE_DENORM
          (excepts & FE_DIVBYZERO ? ExceptionFlags::DIV_BY_ZERO : 0) |
-         (excepts & FE_OVERFLOW ? ExceptionFlags::OVERFLOW : 0) |
-         (excepts & FE_UNDERFLOW ? ExceptionFlags::UNDERFLOW : 0) |
+         (excepts & FE_OVERFLOW ? ExceptionFlags::OVERFLOW_F : 0) |
+         (excepts & FE_UNDERFLOW ? ExceptionFlags::UNDERFLOW_F : 0) |
          (excepts & FE_INEXACT ? ExceptionFlags::INEXACT : 0);
 }
 
@@ -87,8 +87,8 @@
          (status & ExceptionFlags::DENORMAL ? __FE_DENORM : 0) |
 #endif // __FE_DENORM
          (status & ExceptionFlags::DIV_BY_ZERO ? FE_DIVBYZERO : 0) |
-         (status & ExceptionFlags::OVERFLOW ? FE_OVERFLOW : 0) |
-         (status & ExceptionFlags::UNDERFLOW ? FE_UNDERFLOW : 0) |
+         (status & ExceptionFlags::OVERFLOW_F ? FE_OVERFLOW : 0) |
+         (status & ExceptionFlags::UNDERFLOW_F ? FE_UNDERFLOW : 0) |
          (status & ExceptionFlags::INEXACT ? FE_INEXACT : 0);
 }
 
@@ -267,10 +267,10 @@
     raise_helper(internal::ExceptionFlags::INVALID);
   if (status_value & internal::ExceptionFlags::DIV_BY_ZERO)
     raise_helper(internal::ExceptionFlags::DIV_BY_ZERO);
-  if (status_value & internal::ExceptionFlags::OVERFLOW)
-    raise_helper(internal::ExceptionFlags::OVERFLOW);
-  if (status_value & internal::ExceptionFlags::UNDERFLOW)
-    raise_helper(internal::ExceptionFlags::UNDERFLOW);
+  if (status_value & internal::ExceptionFlags::OVERFLOW_F)
+    raise_helper(internal::ExceptionFlags::OVERFLOW_F);
+  if (status_value & internal::ExceptionFlags::UNDERFLOW_F)
+    raise_helper(internal::ExceptionFlags::UNDERFLOW_F);
   if (status_value & internal::ExceptionFlags::INEXACT)
     raise_helper(internal::ExceptionFlags::INEXACT);
 #ifdef __FE_DENORM
@@ -371,24 +371,24 @@
 // The exception flags in the Windows FEnv struct and the MXCSR have almost
 // reversed bit positions.
 struct WinExceptionFlags {
-  static constexpr uint32_t INEXACT = 0x01;
-  static constexpr uint32_t UNDERFLOW = 0x02;
-  static constexpr uint32_t OVERFLOW = 0x04;
-  static constexpr uint32_t DIV_BY_ZERO = 0x08;
-  static constexpr uint32_t INVALID = 0x10;
-  static constexpr uint32_t DENORMAL = 0x20;
+  static constexpr uint32_t INEXACT_WIN = 0x01;
+  static constexpr uint32_t UNDERFLOW_WIN = 0x02;
+  static constexpr uint32_t OVERFLOW_WIN = 0x04;
+  static constexpr uint32_t DIV_BY_ZERO_WIN = 0x08;
+  static constexpr uint32_t INVALID_WIN = 0x10;
+  static constexpr uint32_t DENORMAL_WIN = 0x20;
 
   // The Windows FEnv struct has a second copy of all of these bits in the high
   // byte of the 32 bit control word. These are used as the source of truth when
   // calling fesetenv.
   static constexpr uint32_t HIGH_OFFSET = 24;
 
-  static constexpr uint32_t HIGH_INEXACT = INEXACT << HIGH_OFFSET;
-  static constexpr uint32_t HIGH_UNDERFLOW = UNDERFLOW << HIGH_OFFSET;
-  static constexpr uint32_t HIGH_OVERFLOW = OVERFLOW << HIGH_OFFSET;
-  static constexpr uint32_t HIGH_DIV_BY_ZERO = DIV_BY_ZERO << HIGH_OFFSET;
-  static constexpr uint32_t HIGH_INVALID = INVALID << HIGH_OFFSET;
-  static constexpr uint32_t HIGH_DENORMAL = DENORMAL << HIGH_OFFSET;
+  static constexpr uint32_t HIGH_INEXACT = INEXACT_WIN << HIGH_OFFSET;
+  static constexpr uint32_t HIGH_UNDERFLOW = UNDERFLOW_WIN << HIGH_OFFSET;
+  static constexpr uint32_t HIGH_OVERFLOW = OVERFLOW_WIN << HIGH_OFFSET;
+  static constexpr uint32_t HIGH_DIV_BY_ZERO = DIV_BY_ZERO_WIN << HIGH_OFFSET;
+  static constexpr uint32_t HIGH_INVALID = INVALID_WIN << HIGH_OFFSET;
+  static constexpr uint32_t HIGH_DENORMAL = DENORMAL_WIN << HIGH_OFFSET;
 };
 
 /*
@@ -474,8 +474,8 @@
                            internal::ExceptionFlags::DENORMAL))
                  << 4;
   status_word |= (mxcsr & internal::ExceptionFlags::DIV_BY_ZERO) << 1;
-  status_word |= (mxcsr & internal::ExceptionFlags::OVERFLOW) >> 1;
-  status_word |= (mxcsr & internal::ExceptionFlags::UNDERFLOW) >> 3;
+  status_word |= (mxcsr & internal::ExceptionFlags::OVERFLOW_F) >> 1;
+  status_word |= (mxcsr & internal::ExceptionFlags::UNDERFLOW_F) >> 3;
   status_word |= (mxcsr & internal::ExceptionFlags::INEXACT) >> 5;
   status_word |= status_word << WinExceptionFlags::HIGH_OFFSET;
 
@@ -486,8 +486,8 @@
         << 7)) >>
       3;
   control_word |= (mxcsr & (internal::ExceptionFlags::DIV_BY_ZERO << 7)) >> 6;
-  control_word |= (mxcsr & (internal::ExceptionFlags::OVERFLOW << 7)) >> 8;
-  control_word |= (mxcsr & (internal::ExceptionFlags::UNDERFLOW << 7)) >> 10;
+  control_word |= (mxcsr & (internal::ExceptionFlags::OVERFLOW_F << 7)) >> 8;
+  control_word |= (mxcsr & (internal::ExceptionFlags::UNDERFLOW_F << 7)) >> 10;
   control_word |= (mxcsr & (internal::ExceptionFlags::INEXACT << 7)) >> 12;
   control_word |= control_word << WinExceptionFlags::HIGH_OFFSET;