gdbinit.in: add "break-on-diagnostic" command

gcc/ChangeLog:
	* gdbinit.in (break-on-diagnostic): New command.

From-SVN: r254877

gcc/ChangeLog

+2017-11-17  David Malcolm  <dmalcolm@redhat.com>
+
+	* gdbinit.in (break-on-diagnostic): New command.
+
 2017-11-17  Igor Tsimbalist  <igor.v.tsimbalist@intel.com>
 
 	* config/i386/i386.c (ix86_expand_epilogue): Change simple

gcc/gdbinit.in

@@ -208,6 +208,16 @@ document pcfun
 Print current function.
 end
 
+define break-on-diagnostic
+break diagnostic_show_locus
+end
+
+document break-on-diagnostic
+Put a breakpoint on diagnostic_show_locus, called whenever a diagnostic
+is emitted (as opposed to those warnings that are suppressed by
+command-line options).
+end
+
 # Define some macros helpful to gdb when it is expanding macros.
 macro define __FILE__ "gdb"
 macro define __LINE__ 1