diff --git a/std/cstr.zig b/std/cstr.zig
index 7e61381b9..e29f90fc0 100644
--- a/std/cstr.zig
+++ b/std/cstr.zig
@@ -45,5 +45,5 @@ pub fn addNullByte(allocator: &mem.Allocator, slice: []const u8) -> %[]u8 {
     const result = %return allocator.alloc(u8, slice.len + 1);
     mem.copy(u8, result, slice);
     result[slice.len] = 0;
-    return result[0..slice.len];
+    return result;
 }
diff --git a/std/os/index.zig b/std/os/index.zig
index a9d91972b..0b536d319 100644
--- a/std/os/index.zig
+++ b/std/os/index.zig
@@ -322,7 +322,7 @@ pub fn createNullDelimitedEnvMap(allocator: &Allocator, env_map: &const BufMap)
 
 pub fn freeNullDelimitedEnvMap(allocator: &Allocator, envp_buf: []?&u8) {
     for (envp_buf) |env| {
-        const env_buf = if (env) |ptr| cstr.toSlice(ptr) else break;
+        const env_buf = if (env) |ptr| ptr[0 .. cstr.len(ptr) + 1] else break;
         allocator.free(env_buf);
     }
     allocator.free(envp_buf);
@@ -490,6 +490,28 @@ test "os.getCwd" {
 }
 
 pub fn symLink(allocator: &Allocator, existing_path: []const u8, new_path: []const u8) -> %void {
+    if (is_windows) {
+        return symLinkWindows(allocator, existing_path, new_path);
+    } else {
+        return symLinkPosix(allocator, existing_path, new_path);
+    }
+}
+
+pub fn symLinkWindows(allocator: &Allocator, existing_path: []const u8, new_path: []const u8) -> %void {
+    const existing_with_null = %return cstr.addNullByte(allocator, existing_path);
+    defer allocator.free(existing_with_null);
+    const new_with_null = %return cstr.addNullByte(allocator, new_path);
+    defer allocator.free(new_with_null);
+
+    if (windows.CreateSymbolicLinkA(existing_with_null.ptr, new_with_null.ptr, 0) == 0) {
+        const err = windows.GetLastError();
+        return switch (err) {
+            else => error.Unexpected,
+        };
+    }
+}
+
+pub fn symLinkPosix(allocator: &Allocator, existing_path: []const u8, new_path: []const u8) -> %void {
     const full_buf = %return allocator.alloc(u8, existing_path.len + new_path.len + 2);
     defer allocator.free(full_buf);
 
diff --git a/std/os/windows/index.zig b/std/os/windows/index.zig
index 424b3eba4..eb066c7aa 100644
--- a/std/os/windows/index.zig
+++ b/std/os/windows/index.zig
@@ -25,6 +25,9 @@ pub extern "kernel32" stdcallcc fn CreateProcessA(lpApplicationName: ?LPCSTR, lp
     dwCreationFlags: DWORD, lpEnvironment: ?LPVOID, lpCurrentDirectory: ?LPCSTR, lpStartupInfo: &STARTUPINFOA,
     lpProcessInformation: &PROCESS_INFORMATION) -> BOOL;
 
+pub extern "kernel32" stdcallcc fn CreateSymbolicLinkA(lpSymlinkFileName: LPCSTR, lpTargetFileName: LPCSTR,
+    dwFlags: DWORD) -> BOOLEAN;
+
 pub extern "kernel32" stdcallcc fn DeleteFileA(lpFileName: LPCSTR) -> bool;
 
 pub extern "kernel32" stdcallcc fn ExitProcess(exit_code: UINT) -> noreturn;
@@ -74,34 +77,34 @@ pub extern "user32" stdcallcc fn MessageBoxA(hWnd: ?HANDLE, lpText: ?LPCTSTR, lp
 
 pub const PROV_RSA_FULL = 1;
 
-pub const UNICODE = false;
-pub const LPTSTR = if (UNICODE) LPWSTR else LPSTR;
-pub const LPWSTR = &WCHAR;
-pub const LPSTR = &CHAR;
-pub const CHAR = u8;
-pub const PWSTR = &WCHAR;
-pub const SIZE_T = usize;
-
 pub const BOOL = bool;
+pub const BOOLEAN = BYTE;
 pub const BYTE = u8;
-pub const WORD = u16;
+pub const CHAR = u8;
 pub const DWORD = u32;
 pub const FLOAT = f32;
 pub const HANDLE = &c_void;
-pub const HINSTANCE = &@OpaqueType();
 pub const HCRYPTPROV = ULONG_PTR;
-pub const LPCTSTR = &const TCHAR;
+pub const HINSTANCE = &@OpaqueType();
+pub const INT = c_int;
+pub const LPBYTE = &BYTE;
 pub const LPCSTR = &const CHAR;
+pub const LPCTSTR = &const TCHAR;
+pub const LPCVOID = &const c_void;
 pub const LPDWORD = &DWORD;
+pub const LPSTR = &CHAR;
+pub const LPTSTR = if (UNICODE) LPWSTR else LPSTR;
 pub const LPVOID = &c_void;
+pub const LPWSTR = &WCHAR;
 pub const PVOID = &c_void;
+pub const PWSTR = &WCHAR;
+pub const SIZE_T = usize;
 pub const TCHAR = if (UNICODE) WCHAR else u8;
 pub const UINT = c_uint;
-pub const INT = c_int;
 pub const ULONG_PTR = usize;
+pub const UNICODE = false;
 pub const WCHAR = u16;
-pub const LPCVOID = &const c_void;
-pub const LPBYTE = &BYTE;
+pub const WORD = u16;
 
 /// The standard input device. Initially, this is the console input buffer, CONIN$.
 pub const STD_INPUT_HANDLE = @maxValue(DWORD) - 10 + 1;