+/* This function is never called. Its purpose is to prevent
+ print_output_debug_flag from being optimized away. */
+
+void
+debug_output_compilation_hack (x)
+ int x;
+{
+ print_output_debug_flag = x;
+}
+
+#if defined (GNU_LINUX)
+
+/* This functionality is not vitally important in general, so we rely on
+ non-portable ability to use stderr as lvalue. */
+
+#define WITH_REDIRECT_DEBUGGING_OUTPUT 1
+
+FILE *initial_stderr_stream = NULL;
+
+DEFUN ("redirect-debugging-output", Fredirect_debugging_output, Sredirect_debugging_output,
+ 1, 2,
+ "FDebug output file: \nP",
+ doc: /* Redirect debugging output (stderr stream) to file FILE.
+If FILE is nil, reset target to the initial stderr stream.
+Optional arg APPEND non-nil (interactively, with prefix arg) means
+append to existing target file. */)
+ (file, append)
+ Lisp_Object file, append;
+{
+ if (initial_stderr_stream != NULL)
+ fclose (stderr);
+ stderr = initial_stderr_stream;
+ initial_stderr_stream = NULL;
+
+ if (STRINGP (file))
+ {
+ file = Fexpand_file_name (file, Qnil);
+ initial_stderr_stream = stderr;
+ stderr = fopen (SDATA (file), NILP (append) ? "w" : "a");
+ if (stderr == NULL)
+ {
+ stderr = initial_stderr_stream;
+ initial_stderr_stream = NULL;
+ report_file_error ("Cannot open debugging output stream",
+ Fcons (file, Qnil));
+ }
+ }
+ return Qnil;
+}
+#endif /* GNU_LINUX */
+
+