[RFC] Wrong hw_watchpoint_used_count? (multiple location watchpoints)

[Joel Brobecker <brobecker@adacore.com>]

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This is mostly from code inspection, while investigating something else,
but I think that the current implementation of hw_watchpoint_used_count
is inaccurate. It counts the number of breakpoints which match the given
type.  But in fact, when I looked at the way the watchpoint is created,
watchpoints may have multiple bp_locations. So, a better approximation
would be to count the number of bp_locations, no?

Even so, this does not appear to be entirely accurate either. For
instance, if the user tries to watch an entity that does not fit
in one watchpoint, I think we can still end up with a situation
where we have one bp_location needing 2 h/w watchpoints.
In the end, it looks like the only way to really clean things up
would be to store for each watchpoint the associated number of
needed hardware watchpoints...

I thought about making the following change.  It's not clear that it is
a step in the right direction or not.  Pragmatically, I think it gives
more accurate results.  In terms of implementation, if we eventually
decide to store the mem_cnt in the breakpoint, then we'll have to
go back to iterating over all breakpoints (not bp_locations)...

When in doubt, do nothing?

        * breakpoint.c (hw_watchpoint_used_count): Compute the number
        of hardware watchpoints by iterating over all bp_locations
        instead of all breakpoints.

Tested on x86_64-linux. No regression...

-- 
Joel

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From 6b81fca8153717a836ecee2d4e7ce891b3d32a6e Mon Sep 17 00:00:00 2001
From: Joel Brobecker <brobecker@adacore.com>
Date: Tue, 29 Dec 2009 19:06:50 +0400
Subject: [PATCH] Wrong hw_watchpoint_used_count? (multiple location watchpoints)

        * breakpoint.c (hw_watchpoint_used_count): Compute the number
        of hardware watchpoints by iterating over all bp_locations
        instead of all breakpoints.

---
 gdb/breakpoint.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 0dc8474..91587cb 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -5820,12 +5820,14 @@ hw_breakpoint_used_count (void)
 static int
 hw_watchpoint_used_count (enum bptype type, int *other_type_used)
 {
-  struct breakpoint *b;
+  struct bp_location *loc, **loc_temp;
   int i = 0;
 
   *other_type_used = 0;
-  ALL_BREAKPOINTS (b)
+  ALL_BP_LOCATIONS (loc, loc_temp)
   {
+    struct breakpoint *b = loc->owner;
+
     if (breakpoint_enabled (b))
       {
 	if (b->type == type)
-- 
1.6.3.3