+static int mingw_open_append(wchar_t const *wfilename, int oflags, ...)
+{
+ HANDLE handle;
+ int fd;
+ DWORD create = (oflags & O_CREAT) ? OPEN_ALWAYS : OPEN_EXISTING;
+
+ /* only these flags are supported */
+ if ((oflags & ~O_CREAT) != (O_WRONLY | O_APPEND))
+ return errno = ENOSYS, -1;
+
+ /*
+ * FILE_SHARE_WRITE is required to permit child processes
+ * to append to the file.
+ */
+ handle = CreateFileW(wfilename, FILE_APPEND_DATA,
+ FILE_SHARE_WRITE | FILE_SHARE_READ,
+ NULL, create, FILE_ATTRIBUTE_NORMAL, NULL);
+ if (handle == INVALID_HANDLE_VALUE)
+ return errno = err_win_to_posix(GetLastError()), -1;
+ /*
+ * No O_APPEND here, because the CRT uses it only to reset the
+ * file pointer to EOF on write(); but that is not necessary
+ * for a file created with FILE_APPEND_DATA.
+ */
+ fd = _open_osfhandle((intptr_t)handle, O_BINARY);
+ if (fd < 0)
+ CloseHandle(handle);
+ return fd;
+}
+