Fix PR cli/15603

This fixes PR cli/15603.

The bug here is that when a software watchpoint is being used, gdb
will stop responding to C-c.  This is a regression caused by the
"catch signal" patch.

The problem is that software watchpoints always end up on the bpstat
list.  However, this makes bpstat_explains_signal return
BPSTAT_SIGNAL_HIDE, causing infrun to think that the signal is not a
"random signal".

The fix is to change bpstat_explains_signal to handle this better.  I
chose to do it in a "clean API" way, by passing the signal value to
bpstat_explains_signal and then adding an explains_signal method for
watchpoints, which handles the specifics.

Built and regtested on x86-64 Fedora 18.
New test case included.

	* break-catch-sig.c (signal_catchpoint_explains_signal): Add 'sig'
	argument.
	* breakpoint.c (bpstat_explains_signal): Add 'sig' argument.
	Special case signals other than GDB_SIGNAL_TRAP.
	(explains_signal_watchpoint): New function.
	(base_breakpoint_explains_signal): Add 'sig' argument.
	(initialize_breakpoint_ops): Set 'explains_signal' method for
	watchpoints.
	* breakpoint.h (struct breakpoint_ops) <explains_signal>: Add
	signal argument.
	(bpstat_explains_signal): Likewise.
	* infrun.c (handle_syscall_event, handle_inferior_event): Update.

	* gdb.base/random-signal.c: New file.
	* gdb.base/random-signal.exp: New file.

1 files changed, 30 insertions, 5 deletions

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index d4ccc81..f4933fc 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -4153,7 +4153,7 @@ bpstat_find_breakpoint (bpstat bsp, struct breakpoint *breakpoint)
 /* See breakpoint.h.  */
 
 enum bpstat_signal_value
-bpstat_explains_signal (bpstat bsp)
+bpstat_explains_signal (bpstat bsp, enum gdb_signal sig)
 {
   enum bpstat_signal_value result = BPSTAT_SIGNAL_NO;
 
@@ -4161,10 +4161,20 @@ bpstat_explains_signal (bpstat bsp)
     {
       /* Ensure that, if we ever entered this loop, then we at least
 	 return BPSTAT_SIGNAL_HIDE.  */
-      enum bpstat_signal_value newval = BPSTAT_SIGNAL_HIDE;
+      enum bpstat_signal_value newval;
 
-      if (bsp->breakpoint_at != NULL)
-	newval = bsp->breakpoint_at->ops->explains_signal (bsp->breakpoint_at);
+      if (bsp->breakpoint_at == NULL)
+	{
+	  /* A moribund location can never explain a signal other than
+	     GDB_SIGNAL_TRAP.  */
+	  if (sig == GDB_SIGNAL_TRAP)
+	    newval = BPSTAT_SIGNAL_HIDE;
+	  else
+	    newval = BPSTAT_SIGNAL_NO;
+	}
+      else
+	newval = bsp->breakpoint_at->ops->explains_signal (bsp->breakpoint_at,
+							   sig);
 
       if (newval > result)
 	result = newval;
@@ -10630,6 +10640,20 @@ print_recreate_watchpoint (struct breakpoint *b, struct ui_file *fp)
   print_recreate_thread (b, fp);
 }
 
+/* Implement the "explains_signal" breakpoint_ops method for
+   watchpoints.  */
+
+static enum bpstat_signal_value
+explains_signal_watchpoint (struct breakpoint *b, enum gdb_signal sig)
+{
+  /* A software watchpoint cannot cause a signal other than
+     GDB_SIGNAL_TRAP.  */
+  if (b->type == bp_watchpoint && sig != GDB_SIGNAL_TRAP)
+    return BPSTAT_SIGNAL_NO;
+
+  return BPSTAT_SIGNAL_HIDE;
+}
+
 /* The breakpoint_ops structure to be used in hardware watchpoints.  */
 
 static struct breakpoint_ops watchpoint_breakpoint_ops;
@@ -12733,7 +12757,7 @@ base_breakpoint_decode_linespec (struct breakpoint *b, char **s,
 /* The default 'explains_signal' method.  */
 
 static enum bpstat_signal_value
-base_breakpoint_explains_signal (struct breakpoint *b)
+base_breakpoint_explains_signal (struct breakpoint *b, enum gdb_signal sig)
 {
   return BPSTAT_SIGNAL_HIDE;
 }
@@ -15743,6 +15767,7 @@ initialize_breakpoint_ops (void)
   ops->print_it = print_it_watchpoint;
   ops->print_mention = print_mention_watchpoint;
   ops->print_recreate = print_recreate_watchpoint;
+  ops->explains_signal = explains_signal_watchpoint;
 
   /* Masked watchpoints.  */
   ops = &masked_watchpoint_breakpoint_ops;