http://sourceware.org/ml/gdb-patches/2013-06/msg00788.html
Subject: [PATCH] "enable count" user input error handling (PR gdb/15678)

Typing "enable count" by itself crashes GDB. Also, if you omit the
breakpoint number/range, the error message is not very clear:

(gdb) enable count 2
warning: bad breakpoint number at or near ''
(gdb) enable count
Segmentation fault (core dumped)

With this patch, the error messages are slightly more helpful:

(gdb) enable count 2
Argument required (one or more breakpoint numbers).
(gdb) enable count
Argument required (hit count).

They are not as helpful to the user as I would like, but it's better
than crashing. Suggestions are welcome.

Simon

gdb/ChangeLog:
2013-06-26  Simon Marchi  <simon.marchi@ericsson.com>

	* breakpoint.c (map_breakpoint_numbers): Check for empty args
	string.
	(enable_count_command): Check args for NULL value.

gdb/testsuite/ChangeLog:
2013-06-26  Simon Marchi  <simon.marchi@ericsson.com>

	* gdb.base/ena-dis-br.exp: Test "enable count" for bad user input.
---
 gdb/breakpoint.c                      | 9 +++++++--
 gdb/testsuite/gdb.base/ena-dis-br.exp | 8 ++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

Index: gdb-7.8.50.20141228/gdb/breakpoint.c
===================================================================
--- gdb-7.8.50.20141228.orig/gdb/breakpoint.c	2015-01-05 22:21:47.631801558 +0100
+++ gdb-7.8.50.20141228/gdb/breakpoint.c	2015-01-05 22:26:13.165005049 +0100
@@ -14849,7 +14849,7 @@ map_breakpoint_numbers (char *args, void
   int match;
   struct get_number_or_range_state state;
 
-  if (args == 0)
+  if (args == 0 || *args == '\0')
     error_no_arg (_("one or more breakpoint numbers"));
 
   init_number_or_range (&state, args);
@@ -15186,7 +15186,12 @@ do_map_enable_count_breakpoint (struct b
 static void
 enable_count_command (char *args, int from_tty)
 {
-  int count = get_number (&args);
+  int count;
+
+  if (args == NULL)
+    error_no_arg (_("hit count"));
+
+  count = get_number (&args);
 
   map_breakpoint_numbers (args, do_map_enable_count_breakpoint, &count);
 }
Index: gdb-7.8.50.20141228/gdb/testsuite/gdb.base/ena-dis-br.exp
===================================================================
--- gdb-7.8.50.20141228.orig/gdb/testsuite/gdb.base/ena-dis-br.exp	2015-01-05 22:26:13.165005049 +0100
+++ gdb-7.8.50.20141228/gdb/testsuite/gdb.base/ena-dis-br.exp	2015-01-05 22:26:51.357178150 +0100
@@ -151,6 +151,14 @@ set bp [break_at $bp_location7 "line $bp
 
 set bp2 [break_at marker1 " line $bp_location15"]
 
+gdb_test "enable count" \
+    "Argument required \\(hit count\\)\\." \
+    "enable count missing arguments"
+
+gdb_test "enable count 2" \
+    "Argument required \\(one or more breakpoint numbers\\)\\." \
+    "enable count missing last argument"
+
 gdb_test_no_output "enable count 2 $bp" "disable break with count"
 
 gdb_test "continue" \