Index: gdb-7.12.50.20170207/gdb/valops.c

===================================================================

--- gdb-7.12.50.20170207.orig/gdb/valops.c	2017-02-26 17:26:43.839146565 +0100

+++ gdb-7.12.50.20170207/gdb/valops.c	2017-02-26 17:28:40.840988272 +0100

@@ -1112,6 +1112,8 @@

 	struct gdbarch *gdbarch;

 	int value_reg;

+	value_reg = VALUE_REGNUM (toval);

+

 	/* Figure out which frame this is in currently.

 	   We use VALUE_FRAME_ID for obtaining the value's frame id instead of

@@ -1121,8 +1123,14 @@

 	   frame.  */

 	frame = frame_find_by_id (VALUE_FRAME_ID (toval));

-	value_reg = VALUE_REGNUM (toval);

-

+	/* "set $reg+=1" should work on programs with no debug info,

+	   but frame_find_by_id returns NULL here (RH bug 436037).

+	   Use current frame, it represents CPU state in this case.

+	   If frame_find_by_id is changed to do it internally

+	   (it is contemplated there), remove this.  */

+	if (!frame)

+	  frame = get_current_frame ();

+	/* Probably never happens.  */

 	if (!frame)

 	  error (_("Value being assigned to is no longer active."));