diff --git a/libc/src/sys/mman/linux/madvise.cpp b/libc/src/sys/mman/linux/madvise.cpp
--- a/libc/src/sys/mman/linux/madvise.cpp
+++ b/libc/src/sys/mman/linux/madvise.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -25,7 +25,7 @@
   // A negative return value indicates an error with the magnitude of the
   // value being the error code.
   if (ret_val < 0) {
-    errno = -ret_val;
+    libc_errno = -ret_val;
     return -1;
   }
 
diff --git a/libc/src/sys/mman/linux/mmap.cpp b/libc/src/sys/mman/linux/mmap.cpp
--- a/libc/src/sys/mman/linux/mmap.cpp
+++ b/libc/src/sys/mman/linux/mmap.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <linux/param.h> // For EXEC_PAGESIZE.
 #include <sys/syscall.h> // For syscall numbers.
 
@@ -53,7 +53,7 @@
   // return value corresponding to a location in the last page is an error
   // value.
   if (ret_val < 0 && ret_val > -EXEC_PAGESIZE) {
-    errno = -ret_val;
+    libc_errno = -ret_val;
     return MAP_FAILED;
   }
 
diff --git a/libc/src/sys/mman/linux/mprotect.cpp b/libc/src/sys/mman/linux/mprotect.cpp
--- a/libc/src/sys/mman/linux/mprotect.cpp
+++ b/libc/src/sys/mman/linux/mprotect.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -25,7 +25,7 @@
   // A negative return value indicates an error with the magnitude of the
   // value being the error code.
   if (ret_val < 0) {
-    errno = -ret_val;
+    libc_errno = -ret_val;
     return -1;
   }
 
diff --git a/libc/src/sys/mman/linux/munmap.cpp b/libc/src/sys/mman/linux/munmap.cpp
--- a/libc/src/sys/mman/linux/munmap.cpp
+++ b/libc/src/sys/mman/linux/munmap.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <sys/syscall.h>          // For syscall numbers.
 
 namespace __llvm_libc {
@@ -25,7 +25,7 @@
   // A negative return value indicates an error with the magnitude of the
   // value being the error code.
   if (ret_val < 0) {
-    errno = -ret_val;
+    libc_errno = -ret_val;
     return -1;
   }
 
diff --git a/libc/src/sys/random/linux/getrandom.cpp b/libc/src/sys/random/linux/getrandom.cpp
--- a/libc/src/sys/random/linux/getrandom.cpp
+++ b/libc/src/sys/random/linux/getrandom.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -20,7 +20,7 @@
                    (void *buf, size_t buflen, unsigned int flags)) {
   long ret = __llvm_libc::syscall_impl(SYS_getrandom, buf, buflen, flags);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return 0;
diff --git a/libc/src/sys/resource/linux/getrlimit.cpp b/libc/src/sys/resource/linux/getrlimit.cpp
--- a/libc/src/sys/resource/linux/getrlimit.cpp
+++ b/libc/src/sys/resource/linux/getrlimit.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <sys/resource.h> // For struct rlimit
 #include <sys/syscall.h>  // For syscall numbers.
 
@@ -20,7 +20,7 @@
 LLVM_LIBC_FUNCTION(int, getrlimit, (int res, struct rlimit *limits)) {
   long ret = __llvm_libc::syscall_impl(SYS_prlimit64, 0, res, nullptr, limits);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return 0;
diff --git a/libc/src/sys/resource/linux/setrlimit.cpp b/libc/src/sys/resource/linux/setrlimit.cpp
--- a/libc/src/sys/resource/linux/setrlimit.cpp
+++ b/libc/src/sys/resource/linux/setrlimit.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <sys/resource.h> // For struct rlimit
 #include <sys/syscall.h>  // For syscall numbers.
 
@@ -20,7 +20,7 @@
 LLVM_LIBC_FUNCTION(int, setrlimit, (int res, const struct rlimit *limits)) {
   long ret = __llvm_libc::syscall_impl(SYS_prlimit64, 0, res, limits, nullptr);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return 0;
diff --git a/libc/src/sys/select/linux/select.cpp b/libc/src/sys/select/linux/select.cpp
--- a/libc/src/sys/select/linux/select.cpp
+++ b/libc/src/sys/select/linux/select.cpp
@@ -12,7 +12,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <signal.h>
 #include <stddef.h> // For size_t
 #include <sys/select.h>
@@ -56,7 +56,7 @@
   long ret = __llvm_libc::syscall_impl(SYS_pselect6, nfds, read_set, write_set,
                                        error_set, &ts, &pss);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;
diff --git a/libc/src/sys/sendfile/linux/sendfile.cpp b/libc/src/sys/sendfile/linux/sendfile.cpp
--- a/libc/src/sys/sendfile/linux/sendfile.cpp
+++ b/libc/src/sys/sendfile/linux/sendfile.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <sys/sendfile.h>
 #include <sys/syscall.h> // For syscall numbers.
 
@@ -22,7 +22,7 @@
   long ret =
       __llvm_libc::syscall_impl(SYS_sendfile, in_fd, out_fd, offset, count);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;
diff --git a/libc/src/sys/stat/linux/chmod.cpp b/libc/src/sys/stat/linux/chmod.cpp
--- a/libc/src/sys/stat/linux/chmod.cpp
+++ b/libc/src/sys/stat/linux/chmod.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/syscall.h> // For syscall numbers.
@@ -28,7 +28,7 @@
 #endif
 
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return 0;
diff --git a/libc/src/sys/stat/linux/fchmod.cpp b/libc/src/sys/stat/linux/fchmod.cpp
--- a/libc/src/sys/stat/linux/fchmod.cpp
+++ b/libc/src/sys/stat/linux/fchmod.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/syscall.h> // For syscall numbers.
@@ -21,7 +21,7 @@
 LLVM_LIBC_FUNCTION(int, fchmod, (int fd, mode_t mode)) {
   long ret = __llvm_libc::syscall_impl(SYS_fchmod, fd, mode);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return 0;
diff --git a/libc/src/sys/stat/linux/fchmodat.cpp b/libc/src/sys/stat/linux/fchmodat.cpp
--- a/libc/src/sys/stat/linux/fchmodat.cpp
+++ b/libc/src/sys/stat/linux/fchmodat.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <sys/stat.h>
 #include <sys/syscall.h> // For syscall numbers.
 
@@ -21,7 +21,7 @@
                    (int dirfd, const char *path, mode_t mode, int flags)) {
   long ret = __llvm_libc::syscall_impl(SYS_fchmodat, dirfd, path, mode, flags);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return 0;
diff --git a/libc/src/sys/stat/linux/mkdir.cpp b/libc/src/sys/stat/linux/mkdir.cpp
--- a/libc/src/sys/stat/linux/mkdir.cpp
+++ b/libc/src/sys/stat/linux/mkdir.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/syscall.h> // For syscall numbers.
@@ -28,7 +28,7 @@
 #endif
 
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return 0;
diff --git a/libc/src/sys/stat/linux/mkdirat.cpp b/libc/src/sys/stat/linux/mkdirat.cpp
--- a/libc/src/sys/stat/linux/mkdirat.cpp
+++ b/libc/src/sys/stat/linux/mkdirat.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <sys/stat.h>
 #include <sys/syscall.h> // For syscall numbers.
 
@@ -25,7 +25,7 @@
 #endif
 
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return 0;
diff --git a/libc/src/sys/utsname/linux/uname.cpp b/libc/src/sys/utsname/linux/uname.cpp
--- a/libc/src/sys/utsname/linux/uname.cpp
+++ b/libc/src/sys/utsname/linux/uname.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <sys/syscall.h> // For syscall numbers.
 #include <sys/utsname.h>
 
@@ -22,7 +22,7 @@
 
   if (ret >= 0)
     return 1;
-  errno = -ret;
+  libc_errno = -ret;
   return -1;
 }
 
diff --git a/libc/src/sys/wait/linux/CMakeLists.txt b/libc/src/sys/wait/linux/CMakeLists.txt
--- a/libc/src/sys/wait/linux/CMakeLists.txt
+++ b/libc/src/sys/wait/linux/CMakeLists.txt
@@ -5,7 +5,6 @@
   HDRS
     ../wait.h
   DEPENDS
-    libc.include.errno
     libc.include.sys_wait
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
@@ -19,7 +18,6 @@
   HDRS
     ../wait4.h
   DEPENDS
-    libc.include.errno
     libc.include.sys_wait
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
@@ -33,7 +31,6 @@
   HDRS
     ../waitpid.h
   DEPENDS
-    libc.include.errno
     libc.include.sys_wait
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
diff --git a/libc/src/sys/wait/linux/wait.cpp b/libc/src/sys/wait/linux/wait.cpp
--- a/libc/src/sys/wait/linux/wait.cpp
+++ b/libc/src/sys/wait/linux/wait.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <sys/syscall.h> // For syscall numbers.
 #include <sys/wait.h>
 
@@ -24,7 +24,7 @@
   pid_t pid = __llvm_libc::syscall_impl(SYS_wait4, -1, wait_status, 0, 0);
   if (pid < 0) {
     // Error case, a child process was not created.
-    errno = -pid;
+    libc_errno = -pid;
     return -1;
   }
 
diff --git a/libc/src/sys/wait/linux/wait4.cpp b/libc/src/sys/wait/linux/wait4.cpp
--- a/libc/src/sys/wait/linux/wait4.cpp
+++ b/libc/src/sys/wait/linux/wait4.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <sys/syscall.h> // For syscall numbers.
 #include <sys/wait.h>
 
@@ -22,7 +22,7 @@
                     struct rusage *usage)) {
   pid = __llvm_libc::syscall_impl(SYS_wait4, pid, wait_status, options, usage);
   if (pid < 0) {
-    errno = -pid;
+    libc_errno = -pid;
     return -1;
   }
   return pid;
diff --git a/libc/src/sys/wait/linux/waitpid.cpp b/libc/src/sys/wait/linux/waitpid.cpp
--- a/libc/src/sys/wait/linux/waitpid.cpp
+++ b/libc/src/sys/wait/linux/waitpid.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include "src/errno/libc_errno.h"
 #include <sys/syscall.h> // For syscall numbers.
 #include <sys/wait.h>
 
@@ -20,7 +20,7 @@
 LLVM_LIBC_FUNCTION(pid_t, waitpid, (pid_t pid, int *wait_status, int options)) {
   pid = __llvm_libc::syscall_impl(SYS_wait4, pid, wait_status, options, 0);
   if (pid < 0) {
-    errno = -pid;
+    libc_errno = -pid;
     return -1;
   }
   return pid;
diff --git a/libc/src/unistd/linux/CMakeLists.txt b/libc/src/unistd/linux/CMakeLists.txt
--- a/libc/src/unistd/linux/CMakeLists.txt
+++ b/libc/src/unistd/linux/CMakeLists.txt
@@ -97,7 +97,6 @@
   HDRS
     ../fork.h
   DEPENDS
-    libc.include.errno
     libc.include.unistd
     libc.include.sys_syscall
     libc.src.__support.threads.fork_callbacks
@@ -113,7 +112,6 @@
   HDRS
     ../execv.h
   DEPENDS
-    libc.include.errno
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
     libc.src.errno.errno
@@ -127,7 +125,6 @@
   HDRS
     ../execve.h
   DEPENDS
-    libc.include.errno
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
     libc.src.errno.errno
@@ -166,7 +163,6 @@
   HDRS
     ../getcwd.h
   DEPENDS
-    libc.include.errno
     libc.include.stdlib
     libc.include.unistd
     libc.include.sys_syscall
@@ -230,7 +226,6 @@
     ../isatty.h
   DEPENDS
     libc.include.unistd
-    libc.include.errno
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
     libc.src.errno.errno
diff --git a/libc/src/unistd/linux/access.cpp b/libc/src/unistd/linux/access.cpp
--- a/libc/src/unistd/linux/access.cpp
+++ b/libc/src/unistd/linux/access.cpp
@@ -11,8 +11,8 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
 #include <fcntl.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -27,7 +27,7 @@
 #endif
 
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return 0;
diff --git a/libc/src/unistd/linux/chdir.cpp b/libc/src/unistd/linux/chdir.cpp
--- a/libc/src/unistd/linux/chdir.cpp
+++ b/libc/src/unistd/linux/chdir.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -19,7 +19,7 @@
 LLVM_LIBC_FUNCTION(int, chdir, (const char *path)) {
   long ret = __llvm_libc::syscall_impl(SYS_chdir, path);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return 0;
diff --git a/libc/src/unistd/linux/close.cpp b/libc/src/unistd/linux/close.cpp
--- a/libc/src/unistd/linux/close.cpp
+++ b/libc/src/unistd/linux/close.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -19,7 +19,7 @@
 LLVM_LIBC_FUNCTION(int, close, (int fd)) {
   long ret = __llvm_libc::syscall_impl(SYS_close, fd);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;
diff --git a/libc/src/unistd/linux/dup.cpp b/libc/src/unistd/linux/dup.cpp
--- a/libc/src/unistd/linux/dup.cpp
+++ b/libc/src/unistd/linux/dup.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -19,7 +19,7 @@
 LLVM_LIBC_FUNCTION(int, dup, (int fd)) {
   long ret = __llvm_libc::syscall_impl(SYS_dup, fd);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;
diff --git a/libc/src/unistd/linux/dup2.cpp b/libc/src/unistd/linux/dup2.cpp
--- a/libc/src/unistd/linux/dup2.cpp
+++ b/libc/src/unistd/linux/dup2.cpp
@@ -11,8 +11,8 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
 #include <fcntl.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -30,7 +30,7 @@
     long ret = __llvm_libc::syscall_impl(SYS_fcntl, oldfd, F_GETFD);
     if (ret >= 0)
       return oldfd;
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   long ret = __llvm_libc::syscall_impl(SYS_dup3, oldfd, newfd, 0);
@@ -38,7 +38,7 @@
 #error "SYS_dup2 and SYS_dup3 not available for the target."
 #endif
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;
diff --git a/libc/src/unistd/linux/dup3.cpp b/libc/src/unistd/linux/dup3.cpp
--- a/libc/src/unistd/linux/dup3.cpp
+++ b/libc/src/unistd/linux/dup3.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -21,7 +21,7 @@
   long ret = __llvm_libc::syscall_impl(SYS_dup3, oldfd, newfd, flags);
   if (ret >= 0)
     return ret;
-  errno = -ret;
+  libc_errno = -ret;
   return -1;
 }
 
diff --git a/libc/src/unistd/linux/execv.cpp b/libc/src/unistd/linux/execv.cpp
--- a/libc/src/unistd/linux/execv.cpp
+++ b/libc/src/unistd/linux/execv.cpp
@@ -12,7 +12,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -21,7 +21,7 @@
   long ret =
       __llvm_libc::syscall_impl(SYS_execve, path, argv, __llvm_libc::environ);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
 
diff --git a/libc/src/unistd/linux/execve.cpp b/libc/src/unistd/linux/execve.cpp
--- a/libc/src/unistd/linux/execve.cpp
+++ b/libc/src/unistd/linux/execve.cpp
@@ -12,7 +12,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -21,7 +21,7 @@
                    (const char *path, char *const argv[], char *const envp[])) {
   long ret = __llvm_libc::syscall_impl(SYS_execve, path, argv, envp);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
 
diff --git a/libc/src/unistd/linux/fchdir.cpp b/libc/src/unistd/linux/fchdir.cpp
--- a/libc/src/unistd/linux/fchdir.cpp
+++ b/libc/src/unistd/linux/fchdir.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -19,7 +19,7 @@
 LLVM_LIBC_FUNCTION(int, fchdir, (int fd)) {
   long ret = __llvm_libc::syscall_impl(SYS_fchdir, fd);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return 0;
diff --git a/libc/src/unistd/linux/fork.cpp b/libc/src/unistd/linux/fork.cpp
--- a/libc/src/unistd/linux/fork.cpp
+++ b/libc/src/unistd/linux/fork.cpp
@@ -13,7 +13,7 @@
 #include "src/__support/threads/fork_callbacks.h"
 #include "src/__support/threads/thread.h" // For thread self object
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -42,7 +42,7 @@
 
   if (ret < 0) {
     // Error case, a child process was not created.
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
 
diff --git a/libc/src/unistd/linux/fsync.cpp b/libc/src/unistd/linux/fsync.cpp
--- a/libc/src/unistd/linux/fsync.cpp
+++ b/libc/src/unistd/linux/fsync.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -19,7 +19,7 @@
 LLVM_LIBC_FUNCTION(int, fsync, (int fd)) {
   long ret = __llvm_libc::syscall_impl(SYS_fsync, fd);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;
diff --git a/libc/src/unistd/linux/ftruncate.cpp b/libc/src/unistd/linux/ftruncate.cpp
--- a/libc/src/unistd/linux/ftruncate.cpp
+++ b/libc/src/unistd/linux/ftruncate.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 #include <unistd.h>
 
@@ -20,7 +20,7 @@
 LLVM_LIBC_FUNCTION(int, ftruncate, (int fd, off_t len)) {
   int ret = __llvm_libc::syscall_impl(SYS_ftruncate, fd, len);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return 0;
diff --git a/libc/src/unistd/linux/getcwd.cpp b/libc/src/unistd/linux/getcwd.cpp
--- a/libc/src/unistd/linux/getcwd.cpp
+++ b/libc/src/unistd/linux/getcwd.cpp
@@ -12,8 +12,8 @@
 #include "src/__support/common.h"
 #include "src/string/allocating_string_utils.h" // For strdup.
 
-#include <errno.h>
 #include <linux/limits.h> // This is safe to include without any name pollution.
+#include <src/errno/libc_errno.h>
 #include <stdlib.h>
 #include <sys/syscall.h> // For syscall numbers.
 
@@ -24,10 +24,10 @@
 bool getcwd_syscall(char *buf, size_t size) {
   int ret = __llvm_libc::syscall_impl(SYS_getcwd, buf, size);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return false;
   } else if (ret == 0 || buf[0] != '/') {
-    errno = ENOENT;
+    libc_errno = ENOENT;
     return false;
   }
   return true;
@@ -46,12 +46,12 @@
       return nullptr;
     auto cwd = internal::strdup(pathbuf);
     if (!cwd) {
-      errno = ENOMEM;
+      libc_errno = ENOMEM;
       return nullptr;
     }
     return *cwd;
   } else if (size == 0) {
-    errno = EINVAL;
+    libc_errno = EINVAL;
     return nullptr;
   }
 
diff --git a/libc/src/unistd/linux/isatty.cpp b/libc/src/unistd/linux/isatty.cpp
--- a/libc/src/unistd/linux/isatty.cpp
+++ b/libc/src/unistd/linux/isatty.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/ioctl.h>   // For ioctl numbers.
 #include <sys/syscall.h> // For syscall numbers.
 
@@ -26,7 +26,7 @@
   if (result == 0)
     return 1;
 
-  errno = -result;
+  libc_errno = -result;
   return 0;
 }
 
diff --git a/libc/src/unistd/linux/link.cpp b/libc/src/unistd/linux/link.cpp
--- a/libc/src/unistd/linux/link.cpp
+++ b/libc/src/unistd/linux/link.cpp
@@ -11,8 +11,8 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
 #include <fcntl.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -27,7 +27,7 @@
 #error "SYS_link or SYS_linkat not available."
 #endif
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;
diff --git a/libc/src/unistd/linux/linkat.cpp b/libc/src/unistd/linux/linkat.cpp
--- a/libc/src/unistd/linux/linkat.cpp
+++ b/libc/src/unistd/linux/linkat.cpp
@@ -11,8 +11,8 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
 #include <fcntl.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -23,7 +23,7 @@
   long ret =
       __llvm_libc::syscall_impl(SYS_linkat, fd1, path1, fd2, path2, flags);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;
diff --git a/libc/src/unistd/linux/lseek.cpp b/libc/src/unistd/linux/lseek.cpp
--- a/libc/src/unistd/linux/lseek.cpp
+++ b/libc/src/unistd/linux/lseek.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 #include <unistd.h>
 
@@ -30,7 +30,7 @@
 #endif
 
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return result;
diff --git a/libc/src/unistd/linux/pread.cpp b/libc/src/unistd/linux/pread.cpp
--- a/libc/src/unistd/linux/pread.cpp
+++ b/libc/src/unistd/linux/pread.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -20,7 +20,7 @@
                    (int fd, void *buf, size_t count, off_t offset)) {
   long ret = __llvm_libc::syscall_impl(SYS_pread64, fd, buf, count, offset);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;
diff --git a/libc/src/unistd/linux/pwrite.cpp b/libc/src/unistd/linux/pwrite.cpp
--- a/libc/src/unistd/linux/pwrite.cpp
+++ b/libc/src/unistd/linux/pwrite.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -20,7 +20,7 @@
                    (int fd, const void *buf, size_t count, off_t offset)) {
   long ret = __llvm_libc::syscall_impl(SYS_pwrite64, fd, buf, count, offset);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;
diff --git a/libc/src/unistd/linux/read.cpp b/libc/src/unistd/linux/read.cpp
--- a/libc/src/unistd/linux/read.cpp
+++ b/libc/src/unistd/linux/read.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -19,7 +19,7 @@
 LLVM_LIBC_FUNCTION(ssize_t, read, (int fd, void *buf, size_t count)) {
   long ret = __llvm_libc::syscall_impl(SYS_read, fd, buf, count);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;
diff --git a/libc/src/unistd/linux/readlink.cpp b/libc/src/unistd/linux/readlink.cpp
--- a/libc/src/unistd/linux/readlink.cpp
+++ b/libc/src/unistd/linux/readlink.cpp
@@ -11,8 +11,8 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
 #include <fcntl.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -29,7 +29,7 @@
 #error "SYS_readlink or SYS_readlinkat not available."
 #endif
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;
diff --git a/libc/src/unistd/linux/readlinkat.cpp b/libc/src/unistd/linux/readlinkat.cpp
--- a/libc/src/unistd/linux/readlinkat.cpp
+++ b/libc/src/unistd/linux/readlinkat.cpp
@@ -11,8 +11,8 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
 #include <fcntl.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -23,7 +23,7 @@
   ssize_t ret =
       __llvm_libc::syscall_impl(SYS_readlinkat, fd, path, buf, bufsize);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;
diff --git a/libc/src/unistd/linux/rmdir.cpp b/libc/src/unistd/linux/rmdir.cpp
--- a/libc/src/unistd/linux/rmdir.cpp
+++ b/libc/src/unistd/linux/rmdir.cpp
@@ -11,8 +11,8 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
 #include <fcntl.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -28,7 +28,7 @@
 #endif
 
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return 0;
diff --git a/libc/src/unistd/linux/symlink.cpp b/libc/src/unistd/linux/symlink.cpp
--- a/libc/src/unistd/linux/symlink.cpp
+++ b/libc/src/unistd/linux/symlink.cpp
@@ -11,8 +11,8 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
 #include <fcntl.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -26,7 +26,7 @@
 #error "SYS_symlink or SYS_symlinkat not available."
 #endif
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;
diff --git a/libc/src/unistd/linux/symlinkat.cpp b/libc/src/unistd/linux/symlinkat.cpp
--- a/libc/src/unistd/linux/symlinkat.cpp
+++ b/libc/src/unistd/linux/symlinkat.cpp
@@ -11,8 +11,8 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
 #include <fcntl.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -21,7 +21,7 @@
                    (const char *path1, int fd, const char *path2)) {
   long ret = __llvm_libc::syscall_impl(SYS_symlinkat, path1, fd, path2);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;
diff --git a/libc/src/unistd/linux/syscall.cpp b/libc/src/unistd/linux/syscall.cpp
--- a/libc/src/unistd/linux/syscall.cpp
+++ b/libc/src/unistd/linux/syscall.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <stdarg.h>
 
 namespace __llvm_libc {
@@ -24,7 +24,7 @@
   // Syscalls may return large positive values that overflow, but will never
   // return values between -4096 and -1
   if (static_cast<unsigned long>(ret) > -4096UL) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;
diff --git a/libc/src/unistd/linux/sysconf.cpp b/libc/src/unistd/linux/sysconf.cpp
--- a/libc/src/unistd/linux/sysconf.cpp
+++ b/libc/src/unistd/linux/sysconf.cpp
@@ -10,8 +10,8 @@
 
 #include "src/__support/common.h"
 
-#include <errno.h>
 #include <linux/param.h> // For EXEC_PAGESIZE.
+#include <src/errno/libc_errno.h>
 #include <unistd.h>
 
 namespace __llvm_libc {
@@ -24,7 +24,7 @@
   }
   // TODO: Complete the rest of the sysconf options.
   if (ret < 0) {
-    errno = EINVAL;
+    libc_errno = EINVAL;
     return -1;
   }
   return ret;
diff --git a/libc/src/unistd/linux/truncate.cpp b/libc/src/unistd/linux/truncate.cpp
--- a/libc/src/unistd/linux/truncate.cpp
+++ b/libc/src/unistd/linux/truncate.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 #include <unistd.h>
 
@@ -20,7 +20,7 @@
 LLVM_LIBC_FUNCTION(int, truncate, (const char *path, off_t len)) {
   int ret = __llvm_libc::syscall_impl(SYS_truncate, path, len);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return 0;
diff --git a/libc/src/unistd/linux/unlink.cpp b/libc/src/unistd/linux/unlink.cpp
--- a/libc/src/unistd/linux/unlink.cpp
+++ b/libc/src/unistd/linux/unlink.cpp
@@ -11,8 +11,8 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
 #include <fcntl.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -27,7 +27,7 @@
 #endif
 
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return 0;
diff --git a/libc/src/unistd/linux/unlinkat.cpp b/libc/src/unistd/linux/unlinkat.cpp
--- a/libc/src/unistd/linux/unlinkat.cpp
+++ b/libc/src/unistd/linux/unlinkat.cpp
@@ -11,8 +11,8 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
 #include <fcntl.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -25,7 +25,7 @@
 #endif
 
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return 0;
diff --git a/libc/src/unistd/linux/write.cpp b/libc/src/unistd/linux/write.cpp
--- a/libc/src/unistd/linux/write.cpp
+++ b/libc/src/unistd/linux/write.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
+#include <src/errno/libc_errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
@@ -19,7 +19,7 @@
 LLVM_LIBC_FUNCTION(ssize_t, write, (int fd, const void *buf, size_t count)) {
   long ret = __llvm_libc::syscall_impl(SYS_write, fd, buf, count);
   if (ret < 0) {
-    errno = -ret;
+    libc_errno = -ret;
     return -1;
   }
   return ret;