[RFAv2 1/2] Fix regression for multi breakpoints command line clearing.

[Philippe Waroquiers <philippe.waroquiers@skynet.be>]

breakpoint.c is modified to fix the regression introduced
when clearing the commands of several breakpoints by giving an empty
list of commands, by just typing "end".
GDB should read an empty list of command once, but it reads
it for each breakpoint, as an empty list of command is NULL,
and NULL is interpreted as 'not having read the command list yet'.

The fix consists in having a boolean set to true once the
command list has been read.

gdb/ChangeLog

2018-08-26  Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* breakpoint.c (commands_command_1): New boolean cmd_read
	to detect cmd was already read.
---
 gdb/breakpoint.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 8f0feaa474..4e7dac5157 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -1219,6 +1219,10 @@ commands_command_1 (const char *arg, int from_tty,
 		    struct command_line *control)
 {
   counted_command_line cmd;
+  /* cmd_read will be true once we have read cmd.  Note that cmd might still be
+     NULL after the call to read_command_lines if the user provides an empty
+     list of command by just typing "end".  */
+  bool cmd_read = false;
 
   std::string new_arg;
 
@@ -1235,8 +1239,9 @@ commands_command_1 (const char *arg, int from_tty,
   map_breakpoint_numbers
     (arg, [&] (breakpoint *b)
      {
-       if (cmd == NULL)
+       if (!cmd_read)
 	 {
+	   gdb_assert (cmd == NULL);
 	   if (control != NULL)
 	     cmd = control->body_list_0;
 	   else
@@ -1256,6 +1261,7 @@ commands_command_1 (const char *arg, int from_tty,
 
 	       cmd = read_command_lines (str.c_str (), from_tty, 1, validator);
 	     }
+	   cmd_read = true;
 	 }
 
        /* If a breakpoint was on the list more than once, we don't need to
-- 
2.18.0