[PATCH 15/23] Make breakpoint_address_bits look at the location kind

[Pedro Alves]

Software watchpoints allocate a special dummy location using
software_watchpoint_add_no_memory_location, and then
breakpoint_address_bits checks whether the location is that special
location to decide whether the location has a meaninful address to
print.

Introduce a new bp_loc_software_watchpoint location kind, and make
breakpoint_address_bits use bl_address_is_meaningful instead, which
returns false for bp_loc_other, which is in accordance with we
document for bp_location::address:

  /* (... snip ...)  Valid for all types except
     bp_loc_other.  */
  CORE_ADDR address = 0;

Rename software_watchpoint_add_no_memory_location to
add_dummy_location, and simplify it.  This will be used by catchpoints
too in a following patch.

Note that neither "info breakpoints" nor "maint info breakpoints"
actually prints the addresses of watchpoints, but I think it would be
useful to do so in "maint info breakpoints".  This approach let's us
implement that in the future.

Change-Id: I50e398f66ef618c31ffa662da755eaba6295aed7
---
 gdb/breakpoint.c | 59 ++++++++++++++++++------------------------------
 gdb/breakpoint.h |  1 +
 2 files changed, 23 insertions(+), 37 deletions(-)

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 6e24137ec4b..6dfb89f51bc 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -164,6 +164,8 @@ static std::vector<symtab_and_line> bkpt_probe_decode_location
       struct event_location *location,
       struct program_space *search_pspace);
 
+static bool bl_address_is_meaningful (bp_location *loc);
+
 /* update_global_location_list's modes of operation wrt to whether to
    insert locations now.  */
 enum ugll_insert_mode
@@ -1830,34 +1832,18 @@ extract_bitfield_from_watchpoint_value (struct watchpoint *w, struct value *val)
   return bit_val;
 }
 
-/* Allocate a dummy location and add it to B, which must be a software
-   watchpoint.  This is required because even if a software watchpoint
-   is not watching any memory, bpstat_stop_status requires a location
-   to be able to report stops.  */
+/* Allocate a dummy location and add it to B.  This is required
+   because bpstat_stop_status requires a location to be able to report
+   stops.  */
 
 static void
-software_watchpoint_add_no_memory_location (struct breakpoint *b,
-					    struct program_space *pspace)
+add_dummy_location (struct breakpoint *b,
+		    struct program_space *pspace)
 {
-  gdb_assert (b->type == bp_watchpoint && b->loc == NULL);
+  gdb_assert (b->loc == NULL);
 
-  b->loc = b->allocate_location ();
+  b->loc = new bp_location (b, bp_loc_other);
   b->loc->pspace = pspace;
-  b->loc->address = -1;
-  b->loc->length = -1;
-}
-
-/* Returns true if B is a software watchpoint that is not watching any
-   memory (e.g., "watch $pc").  */
-
-static bool
-is_no_memory_software_watchpoint (struct breakpoint *b)
-{
-  return (b->type == bp_watchpoint
-	  && b->loc != NULL
-	  && b->loc->next == NULL
-	  && b->loc->address == -1
-	  && b->loc->length == -1);
 }
 
 /* Assuming that B is a watchpoint:
@@ -2197,7 +2183,7 @@ update_watchpoint (struct watchpoint *b, int reparse)
 	  else
 	    b->type = bp_watchpoint;
 
-	  loc_type = (b->type == bp_watchpoint? bp_loc_other
+	  loc_type = (b->type == bp_watchpoint? bp_loc_software_watchpoint
 		      : bp_loc_hardware_watchpoint);
 	  for (bp_location *bl : b->locations ())
 	    bl->loc_type = loc_type;
@@ -2208,7 +2194,7 @@ update_watchpoint (struct watchpoint *b, int reparse)
 	 bpstat_stop_status requires a location to be able to report
 	 stops, so make sure there's at least a dummy one.  */
       if (b->type == bp_watchpoint && b->loc == NULL)
-	software_watchpoint_add_no_memory_location (b, frame_pspace);
+	add_dummy_location (b, frame_pspace);
     }
   else if (!within_current_scope)
     {
@@ -3840,11 +3826,12 @@ detach_breakpoints (ptid_t ptid)
 
       /* This function must physically remove breakpoints locations
 	 from the specified ptid, without modifying the breakpoint
-	 package's state.  Locations of type bp_loc_other are only
-	 maintained at GDB side.  So, there is no need to remove
-	 these bp_loc_other locations.  Moreover, removing these
+	 package's state.  Locations of type bp_loc_other and
+	 bp_loc_software_watchpoint are only maintained at GDB side,
+	 so there is no need to remove them.  Moreover, removing these
 	 would modify the breakpoint package's state.  */
-      if (bl->loc_type == bp_loc_other)
+      if (bl->loc_type == bp_loc_other
+	  || bl->loc_type == bp_loc_software_watchpoint)
 	continue;
 
       if (bl->inserted)
@@ -5798,7 +5785,8 @@ bpstat_what (bpstat *bs_head)
 	    {
 	      /* Some catchpoints are implemented with breakpoints.
 		 For those, we need to step over the breakpoint.  */
-	      if (bs->bp_location_at->loc_type != bp_loc_other)
+	      if (bs->bp_location_at->loc_type == bp_loc_software_breakpoint
+		  || bs->bp_location_at->loc_type == bp_loc_hardware_breakpoint)
 		this_action = BPSTAT_WHAT_SINGLE;
 	    }
 	  break;
@@ -6557,16 +6545,12 @@ breakpoint_address_bits (struct breakpoint *b)
 {
   int print_address_bits = 0;
 
-  /* Software watchpoints that aren't watching memory don't have an
-     address to print.  */
-  if (is_no_memory_software_watchpoint (b))
-    return 0;
-
   for (bp_location *loc : b->locations ())
     {
-      int addr_bit;
+      if (!bl_address_is_meaningful (loc))
+	continue;
 
-      addr_bit = gdbarch_addr_bit (loc->gdbarch);
+      int addr_bit = gdbarch_addr_bit (loc->gdbarch);
       if (addr_bit > print_address_bits)
 	print_address_bits = addr_bit;
     }
@@ -7161,6 +7145,7 @@ bp_location_from_bp_type (bptype type)
     case bp_access_watchpoint:
       return bp_loc_hardware_watchpoint;
     case bp_watchpoint:
+      return bp_loc_software_watchpoint;
     case bp_catchpoint:
     case bp_tracepoint:
     case bp_fast_tracepoint:
diff --git a/gdb/breakpoint.h b/gdb/breakpoint.h
index a4ead8b4d4e..7375e976dc6 100644
--- a/gdb/breakpoint.h
+++ b/gdb/breakpoint.h
@@ -314,6 +314,7 @@ enum bp_loc_type
 {
   bp_loc_software_breakpoint,
   bp_loc_hardware_breakpoint,
+  bp_loc_software_watchpoint,
   bp_loc_hardware_watchpoint,
   bp_loc_other			/* Miscellaneous...  */
 };
-- 
2.36.0