"catch catch/throw/rethrow", breakpoint -> catchpoint

Currently, with:

 (gdb) catch catch
 Catchpoint 1 (catch)
 (gdb) catch throw
 Catchpoint 2 (throw)
 (gdb) catch rethrow
 Catchpoint 3 (rethrow)

You get:

(gdb) info breakpoints
 Num     Type           Disp Enb Address            What
 1       breakpoint     keep y   0x0000000000b122af exception catch
 2       breakpoint     keep y   0x0000000000b1288d exception throw
 3       breakpoint     keep y   0x0000000000b12931 exception rethrow

I think it doesn't make much sense usability-wise, to show a
catchpoint as a breakpoint.  The fact that GDB sets a breakpoint at
some magic address in the C++ run time is an implementation detail,
IMO.  And as seen in the previous patch, such a catchpoint can end up
with more than one location/address even, so showing a single address
isn't entirely accurate.

This commit hides the addresses from view, and makes GDB show
"catchpoint" for type as well:

  (gdb) info breakpoints
  Num     Type           Disp Enb Address            What
  1       catchpoint     keep y                      exception catch
  2       catchpoint     keep y                      exception throw
  3       catchpoint     keep y                      exception rethrow

This comment in the code seems telling:

  /* We need to reset 'type' in order for code in breakpoint.c to do
     the right thing.  */
  cp->type = bp_breakpoint;

It kind of suggests that the reason catchpoints end up shown as
breakpoints was that it was easier to implement them that way, rather
than a desired property.

This commit fixes things up to make it possible to have bp_catch
breakpoints have software/hardware breakpoint locations, thus
eliminating the need for that hack:

 - redo breakpoint_address_is_meaningful in terms of the location's
   type rather than breakpoint type.
 - teach bpstat_what about stepping over the catchpoint locations.
 - install a allocate_location method for "catch catch/throw/rethrow",
   one that forces the location type.

Note that this also reverts the gdb hunk from:

  commit 2a8be20359
  Commit:     Tom Tromey <tom@tromey.com>
  CommitDate: Sat Oct 6 22:17:45 2018 -0600

      Fix Python gdb.Breakpoint.location crash

because now "catch throw" catchpoints hit the

   if (obj->bp->type != bp_breakpoint)
     Py_RETURN_NONE;

check above, and, adjusts the testcase to no longer expect to see the
catchpoint in the gdb.breakpoints() list.

(Note: might make sense to do the same to Ada exception catchpoints.)

gdb/ChangeLog:
2019-07-09  Pedro Alves  <palves@redhat.com>

	* break-catch-throw.c (print_one_exception_catchpoint): Skip the
	"addr" field.
	(allocate_location_exception_catchpoint): New.
	(handle_gnu_v3_exceptions): Don't reset 'type' to bp_breakpoint.
	(initialize_throw_catchpoint_ops): Install
	allocate_location_exception_catchpoint as allocate_location
	method.
	* breakpoint.c (bpstat_what) <bp_catch>: Set action to
	BPSTAT_WHAT_SINGLE if not stopping and the location's type is not
	bp_loc_other.
	(breakpoint_address_is_meaningful): Delete.
	(bl_address_is_meaningful): New.
	(breakpoint_locations_match): Adjust comment.
	(bp_location_from_bp_type): New, factored out of...
	(bp_location::bp_location(breakpoint *)): ... this.
	(bp_location::bp_location(breakpoint *, bp_loc_type)): New,
	factored out of...
	(bp_location::bp_location(breakpoint *)): ... this.  Reimplement.
	(bp_loc_is_permanent): Use bl_address_is_meaningful instead of
	breakpoint_address_is_meaningful.
	(bp_locations_compare): Adjust comment.
	(update_global_location_list): Use bl_address_is_meaningful
	instead of breakpoint_address_is_meaningful.
	* breakpoint.h (bp_location::bp_location(breakpoint *)): New
	explicit.
	(bp_location::bp_location(breakpoint *, bp_loc_type)): Declare.
	* python/py-breakpoint.c (bppy_get_location): No longer check
	whether location is null.

gdb/doc/ChangeLog:
2019-07-09  Pedro Alves  <palves@redhat.com>

	* gdb.texinfo (C++ Exception GDB/MI Catchpoint Commands): Adjust
	examples to show type=catchpoint instead of type=breakpoint and an
	address.

gdb/testsuite/ChangeLog:
2019-07-09  Pedro Alves  <palves@redhat.com>

	* gdb.cp/catch-multi-stdlib.exp: Adjust expected "info
	breakpoints" output.
	* gdb.cp/exception.exp: Adjust expected "info breakpoints" output.
	* gdb.python/py-breakpoint.exp: No longer expect that "catch
	throw" creates breakpoint.
	* gdb.mi/mi-catch-cpp-exceptions.exp (setup_catchpoint): Expect
	'type="catchpoint"'.

gdb/ChangeLog

@@ -1,3 +1,34 @@
+2019-07-09  Pedro Alves  <palves@redhat.com>
+
+	* break-catch-throw.c (print_one_exception_catchpoint): Skip the
+	"addr" field.
+	(allocate_location_exception_catchpoint): New.
+	(handle_gnu_v3_exceptions): Don't reset 'type' to bp_breakpoint.
+	(initialize_throw_catchpoint_ops): Install
+	allocate_location_exception_catchpoint as allocate_location
+	method.
+	* breakpoint.c (bpstat_what) <bp_catch>: Set action to
+	BPSTAT_WHAT_SINGLE if not stopping and the location's type is not
+	bp_loc_other.
+	(breakpoint_address_is_meaningful): Delete.
+	(bl_address_is_meaningful): New.
+	(breakpoint_locations_match): Adjust comment.
+	(bp_location_from_bp_type): New, factored out of...
+	(bp_location::bp_location(breakpoint *)): ... this.
+	(bp_location::bp_location(breakpoint *, bp_loc_type)): New,
+	factored out of...
+	(bp_location::bp_location(breakpoint *)): ... this.  Reimplement.
+	(bp_loc_is_permanent): Use bl_address_is_meaningful instead of
+	breakpoint_address_is_meaningful.
+	(bp_locations_compare): Adjust comment.
+	(update_global_location_list): Use bl_address_is_meaningful
+	instead of breakpoint_address_is_meaningful.
+	* breakpoint.h (bp_location::bp_location(breakpoint *)): New
+	explicit.
+	(bp_location::bp_location(breakpoint *, bp_loc_type)): Declare.
+	* python/py-breakpoint.c (bppy_get_location): No longer check
+	whether location is null.
+
 2019-07-09  Pedro Alves  <palves@redhat.com>
 
 	PR c++/15468

gdb/break-catch-throw.c

@@ -249,18 +249,10 @@ print_one_exception_catchpoint (struct breakpoint *b,
   enum exception_event_kind kind = classify_exception_breakpoint (b);
 
   get_user_print_options (&opts);
+
   if (opts.addressprint)
-    {
+    uiout->field_skip ("addr");
-      annotate_field (4);
-      if (b->loc == NULL || b->loc->shlib_disabled)
-	uiout->field_string ("addr", "<PENDING>");
-      else
-	uiout->field_core_addr ("addr",
-				b->loc->gdbarch, b->loc->address);
-    }
   annotate_field (5);
-  if (b->loc)
-    *last_loc = b->loc;
 
   switch (kind)
     {
@@ -344,6 +336,15 @@ print_recreate_exception_catchpoint (struct breakpoint *b,
   print_recreate_thread (b, fp);
 }
 
+/* Implement the "allocate_location" breakpoint_ops method for throw
+   and catch catchpoints.  */
+
+static bp_location *
+allocate_location_exception_catchpoint (breakpoint *self)
+{
+  return new bp_location (self, bp_loc_software_breakpoint);
+}
+
 static void
 handle_gnu_v3_exceptions (int tempflag, std::string &&except_rx,
 			  const char *cond_string,
@@ -361,9 +362,6 @@ handle_gnu_v3_exceptions (int tempflag, std::string &&except_rx,
 
   init_catchpoint (cp.get (), get_current_arch (), tempflag, cond_string,
 		   &gnu_v3_exception_catchpoint_ops);
-  /* We need to reset 'type' in order for code in breakpoint.c to do
-     the right thing.  */
-  cp->type = bp_breakpoint;
   cp->kind = ex_event;
   cp->exception_rx = std::move (except_rx);
   cp->pattern = std::move (pattern);
@@ -521,6 +519,7 @@ initialize_throw_catchpoint_ops (void)
   ops->print_recreate = print_recreate_exception_catchpoint;
   ops->print_one_detail = print_one_detail_exception_catchpoint;
   ops->check_status = check_status_exception_catchpoint;
+  ops->allocate_location = allocate_location_exception_catchpoint;
 }
 
 void

gdb/breakpoint.c

@@ -5603,8 +5603,10 @@ bpstat_what (bpstat bs_head)
 	    }
 	  else
 	    {
-	      /* There was a catchpoint, but we're not stopping.
+	      /* Some catchpoints are implemented with breakpoints.
-		 This requires no further action.  */
+		 For those, we need to step over the breakpoint.  */
+	      if (bs->bp_location_at->loc_type != bp_loc_other)
+		this_action = BPSTAT_WHAT_SINGLE;
 	    }
 	  break;
 	case bp_jit_event:
@@ -6686,27 +6688,21 @@ describe_other_breakpoints (struct gdbarch *gdbarch,
 }
 
 
-/* Return true iff it is meaningful to use the address member of
+/* Return true iff it is meaningful to use the address member of LOC.
-   BPT locations.  For some breakpoint types, the locations' address members
+   For some breakpoint types, the locations' address members are
-   are irrelevant and it makes no sense to attempt to compare them to other
+   irrelevant and it makes no sense to attempt to compare them to
-   addresses (or use them for any other purpose either).
+   other addresses (or use them for any other purpose either).
 
-   More specifically, each of the following breakpoint types will
+   More specifically, software watchpoints and catchpoints that are
-   always have a zero valued location address and we don't want to mark
+   not backed by breakpoints always have a zero valued location
-   breakpoints of any of these types to be a duplicate of an actual
+   address and we don't want to mark breakpoints of any of these types
-   breakpoint location at address zero:
+   to be a duplicate of an actual breakpoint location at address
+   zero.  */
 
-      bp_watchpoint
+static bool
-      bp_catchpoint
+bl_address_is_meaningful (bp_location *loc)
-
-*/
-
-static int
-breakpoint_address_is_meaningful (struct breakpoint *bpt)
 {
-  enum bptype type = bpt->type;
+  return loc->loc_type != bp_loc_other;
-
-  return (type != bp_watchpoint && type != bp_catchpoint);
 }
 
 /* Assuming LOC1 and LOC2's owners are hardware watchpoints, returns
@@ -6838,8 +6834,8 @@ tracepoint_locations_match (struct bp_location *loc1,
 }
 
 /* Assuming LOC1 and LOC2's types' have meaningful target addresses
-   (breakpoint_address_is_meaningful), returns true if LOC1 and LOC2
+   (bl_address_is_meaningful), returns true if LOC1 and LOC2 represent
-   represent the same location.  */
+   the same location.  */
 
 static int
 breakpoint_locations_match (struct bp_location *loc1, 
@@ -6937,16 +6933,10 @@ adjust_breakpoint_address (struct gdbarch *gdbarch,
     }
 }
 
-bp_location::bp_location (breakpoint *owner)
+static bp_loc_type
+bp_location_from_bp_type (bptype type)
 {
-  bp_location *loc = this;
+  switch (type)
-
-  loc->owner = owner;
-  loc->cond_bytecode = NULL;
-  loc->shlib_disabled = 0;
-  loc->enabled = 1;
-
-  switch (owner->type)
     {
     case bp_breakpoint:
     case bp_single_step:
@@ -6972,30 +6962,44 @@ bp_location::bp_location (breakpoint *owner)
     case bp_gnu_ifunc_resolver:
     case bp_gnu_ifunc_resolver_return:
     case bp_dprintf:
-      loc->loc_type = bp_loc_software_breakpoint;
+      return bp_loc_software_breakpoint;
-      mark_breakpoint_location_modified (loc);
-      break;
     case bp_hardware_breakpoint:
-      loc->loc_type = bp_loc_hardware_breakpoint;
+      return bp_loc_hardware_breakpoint;
-      mark_breakpoint_location_modified (loc);
-      break;
     case bp_hardware_watchpoint:
     case bp_read_watchpoint:
     case bp_access_watchpoint:
-      loc->loc_type = bp_loc_hardware_watchpoint;
+      return bp_loc_hardware_watchpoint;
-      break;
     case bp_watchpoint:
     case bp_catchpoint:
     case bp_tracepoint:
     case bp_fast_tracepoint:
     case bp_static_tracepoint:
-      loc->loc_type = bp_loc_other;
+      return bp_loc_other;
-      break;
     default:
       internal_error (__FILE__, __LINE__, _("unknown breakpoint type"));
     }
+}
 
-  loc->refc = 1;
+bp_location::bp_location (breakpoint *owner, bp_loc_type type)
+{
+  this->owner = owner;
+  this->cond_bytecode = NULL;
+  this->shlib_disabled = 0;
+  this->enabled = 1;
+
+  this->loc_type = type;
+
+  if (this->loc_type == bp_loc_software_breakpoint
+      || this->loc_type == bp_loc_hardware_breakpoint)
+    mark_breakpoint_location_modified (this);
+
+  this->refc = 1;
+}
+
+bp_location::bp_location (breakpoint *owner)
+  : bp_location::bp_location (owner,
+			      bp_location_from_bp_type (owner->type))
+{
 }
 
 /* Allocate a struct bp_location.  */
@@ -8639,11 +8643,12 @@ bp_loc_is_permanent (struct bp_location *loc)
 {
   gdb_assert (loc != NULL);
 
-  /* If we have a catchpoint or a watchpoint, just return 0.  We should not
+  /* If we have a non-breakpoint-backed catchpoint or a software
-     attempt to read from the addresses the locations of these breakpoint types
+     watchpoint, just return 0.  We should not attempt to read from
-     point to.  program_breakpoint_here_p, below, will attempt to read
+     the addresses the locations of these breakpoint types point to.
+     program_breakpoint_here_p, below, will attempt to read
      memory.  */
-  if (!breakpoint_address_is_meaningful (loc->owner))
+  if (!bl_address_is_meaningful (loc))
     return 0;
 
   scoped_restore_current_pspace_and_thread restore_pspace_thread;
@@ -11451,10 +11456,9 @@ breakpoint_auto_delete (bpstat bs)
 
 /* A comparison function for bp_location AP and BP being interfaced to
    qsort.  Sort elements primarily by their ADDRESS (no matter what
-   does breakpoint_address_is_meaningful say for its OWNER),
+   bl_address_is_meaningful says), secondarily by ordering first
-   secondarily by ordering first permanent elements and
+   permanent elements and terciarily just ensuring the array is sorted
-   terciarily just ensuring the array is sorted stable way despite
+   stable way despite qsort being an unstable algorithm.  */
-   qsort being an unstable algorithm.  */
 
 static int
 bp_locations_compare (const void *ap, const void *bp)
@@ -11794,7 +11798,7 @@ update_global_location_list (enum ugll_insert_mode insert_mode)
 		 this one from the target.  */
 
 	      /* OLD_LOC comes from existing struct breakpoint.  */
-	      if (breakpoint_address_is_meaningful (old_loc->owner))
+	      if (bl_address_is_meaningful (old_loc))
 		{
 		  for (loc2p = locp;
 		       (loc2p < bp_locations + bp_locations_count
@@ -11934,7 +11938,7 @@ update_global_location_list (enum ugll_insert_mode insert_mode)
       b = loc->owner;
 
       if (!unduplicated_should_be_inserted (loc)
-	  || !breakpoint_address_is_meaningful (b)
+	  || !bl_address_is_meaningful (loc)
 	  /* Don't detect duplicate for tracepoint locations because they are
 	   never duplicated.  See the comments in field `duplicate' of
 	   `struct bp_location'.  */

gdb/breakpoint.h

@@ -316,7 +316,12 @@ class bp_location
 public:
   bp_location () = default;
 
-  bp_location (breakpoint *owner);
+  /* Construct a bp_location with the type inferred from OWNER's
+     type.  */
+  explicit bp_location (breakpoint *owner);
+
+  /* Construct a bp_location with type TYPE.  */
+  bp_location (breakpoint *owner, bp_loc_type type);
 
   virtual ~bp_location ();
 

gdb/doc/ChangeLog

@@ -1,3 +1,9 @@
+2019-07-09  Pedro Alves  <palves@redhat.com>
+
+	* gdb.texinfo (C++ Exception GDB/MI Catchpoint Commands): Adjust
+	examples to show type=catchpoint instead of type=breakpoint and an
+	address.
+
 2019-07-03  Pedro Alves  <palves@redhat.com>
 	    Philippe Waroquiers  <philippe.waroquiers@skynet.be>
 

gdb/doc/gdb.texinfo

@@ -30120,9 +30120,9 @@ and @samp{tcatch throw} (@pxref{Set Catchpoints}).
 
 @smallexample
 -catch-throw -r exception_type
-^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
+^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
-  addr="0x00000000004006c0",what="exception throw",
+  what="exception throw",catch-type="throw",
-  catch-type="throw",thread-groups=["i1"],
+  thread-groups=["i1"],
   regexp="exception_type",times="0"@}
 (gdb)
 -exec-run
@@ -30164,9 +30164,9 @@ and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
 
 @smallexample
 -catch-rethrow -r exception_type
-^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
+^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
-  addr="0x00000000004006c0",what="exception rethrow",
+  what="exception rethrow",catch-type="rethrow",
-  catch-type="rethrow",thread-groups=["i1"],
+  thread-groups=["i1"],
   regexp="exception_type",times="0"@}
 (gdb)
 -exec-run
@@ -30208,9 +30208,9 @@ and @samp{tcatch catch} (@pxref{Set Catchpoints}).
 
 @smallexample
 -catch-catch -r exception_type
-^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
+^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
-  addr="0x00000000004006c0",what="exception catch",
+  what="exception catch",catch-type="catch",
-  catch-type="catch",thread-groups=["i1"],
+  thread-groups=["i1"],
   regexp="exception_type",times="0"@}
 (gdb)
 -exec-run

gdb/python/py-breakpoint.c

@@ -379,7 +379,6 @@ bppy_set_hit_count (PyObject *self, PyObject *newvalue, void *closure)
 static PyObject *
 bppy_get_location (PyObject *self, void *closure)
 {
-  const char *str;
   gdbpy_breakpoint_object *obj = (gdbpy_breakpoint_object *) self;
 
   BPPY_REQUIRE_VALID (obj);
@@ -387,12 +386,7 @@ bppy_get_location (PyObject *self, void *closure)
   if (obj->bp->type != bp_breakpoint)
     Py_RETURN_NONE;
 
-  struct event_location *location = obj->bp->location.get ();
+  const char *str = event_location_to_string (obj->bp->location.get ());
-  /* "catch throw" makes a breakpoint of type bp_breakpoint that does
-     not have a location.  */
-  if (location == nullptr)
-    Py_RETURN_NONE;
-  str = event_location_to_string (location);
   if (! str)
     str = "";
   return host_string_to_python_string (str).release ();

gdb/testsuite/ChangeLog

@@ -1,3 +1,13 @@
+2019-07-09  Pedro Alves  <palves@redhat.com>
+
+	* gdb.cp/catch-multi-stdlib.exp: Adjust expected "info
+	breakpoints" output.
+	* gdb.cp/exception.exp: Adjust expected "info breakpoints" output.
+	* gdb.python/py-breakpoint.exp: No longer expect that "catch
+	throw" creates breakpoint.
+	* gdb.mi/mi-catch-cpp-exceptions.exp (setup_catchpoint): Expect
+	'type="catchpoint"'.
+
 2019-07-09  Pedro Alves  <palves@redhat.com>
 
 	PR c++/15468

gdb/testsuite/gdb.cp/except-multi-location.exp

@@ -74,9 +74,9 @@ proc test_multi_libstdcpp {static_bin static_lib} {
     set ws "\[ \t\]*"
     gdb_test "info breakpoints" \
 	[multi_line \
-	     "${decimal}${ws}breakpoint${ws}keep${ws}y${ws}${hex}${ws}exception catch" \
+	     "${decimal}${ws}catchpoint${ws}keep${ws}y${ws}exception catch" \
-	     "${decimal}${ws}breakpoint${ws}keep${ws}y${ws}${hex}${ws}exception throw" \
+	     "${decimal}${ws}catchpoint${ws}keep${ws}y${ws}exception throw" \
-	     "${decimal}${ws}breakpoint${ws}keep${ws}y${ws}${hex}${ws}exception rethrow"]
+	     "${decimal}${ws}catchpoint${ws}keep${ws}y${ws}exception rethrow"]
 }
 
 # Try different static/not-static combinations.

gdb/testsuite/gdb.cp/exception.exp

@@ -62,16 +62,10 @@ gdb_test "catch rethrow" "Catchpoint \[0-9\]+ \\(rethrow\\)" \
     "catch rethrow (before inferior run)"
 
 
-# The catchpoints should be listed in the list of breakpoints.
-# In case of a statically linked test, we won't have a pending breakpoint.
-# Hence we allow for both an address or "<PENDING>". If we ever become able
-# to tell whether the target is linked statically or not, we can be more
-# precise and require exact output.
-set addr "\(<PENDING>|$hex\)"
 set re_head	"Num${ws}Type${ws}Disp${ws}Enb${ws}Address${ws}What"
-set re_2_bp	"1${ws}breakpoint${ws}keep${ws}y${ws}$addr${ws}exception catch"
+set re_2_bp	"1${ws}catchpoint${ws}keep${ws}y${ws}exception catch"
-set re_3_bp	"2${ws}breakpoint${ws}keep${ws}y${ws}$addr${ws}exception throw"
+set re_3_bp	"2${ws}catchpoint${ws}keep${ws}y${ws}exception throw"
-set re_4_bp   "3${ws}breakpoint${ws}keep${ws}y${ws}$addr${ws}exception rethrow"
+set re_4_bp	"3${ws}catchpoint${ws}keep${ws}y${ws}exception rethrow"
 
 set name "info breakpoints (before inferior run)"
 gdb_test_multiple "info breakpoints" $name {
@@ -100,12 +94,6 @@ if { !$ok } {
     continue
 }
 
-set addr "$hex"
-set re_head	"Num${ws}Type${ws}Disp${ws}Enb${ws}Address${ws}What"
-set re_2_bp	"1${ws}breakpoint${ws}keep${ws}y${ws}$addr${ws}exception catch"
-set re_3_bp	"2${ws}breakpoint${ws}keep${ws}y${ws}$addr${ws}exception throw"
-set re_4_bp   "3${ws}breakpoint${ws}keep${ws}y${ws}$addr${ws}exception rethrow"
-
 set name "info breakpoints (after inferior run)"
 gdb_test_multiple "info breakpoints" $name {
     -re "$re_head${ws}$re_2_bp${ws}$re_3_bp${ws}$re_4_bp\r\n$gdb_prompt $" {

gdb/testsuite/gdb.mi/mi-catch-cpp-exceptions.exp

@@ -85,7 +85,7 @@ proc continue_to_breakpoint_in_main {} {
 proc setup_catchpoint {type {extra ""}} {
     global decimal
     mi_gdb_test "-catch-${type} ${extra}" \
-	"\\^done,bkpt=\{number=\"$decimal\".*what=\"exception ${type}\",catch-type=\"${type}\".*\}" \
+	"\\^done,bkpt=\{number=\"$decimal\",type=\"catchpoint\".*what=\"exception ${type}\",catch-type=\"${type}\".*\}" \
 	"Setup -catch-${type}"
 }
 

gdb/testsuite/gdb.python/py-breakpoint.exp

@@ -619,8 +619,9 @@ proc_with_prefix test_bkpt_explicit_loc {} {
 
     delete_breakpoints
     gdb_test "catch throw" "Catchpoint .* \\(throw\\)"
-    gdb_test "python print (gdb.breakpoints()\[0\].location)" None \
+    gdb_test "python print (gdb.breakpoints())" \
-	"Examine location of catchpoint"
+	"\(\)" \
+	"catch throw is not a breakpoint"
 }
 
 proc_with_prefix test_bkpt_qualified {} {