"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 2a8be20359dba9cc684fd3ffa222d985399f3b18
  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"'.

2 files changed, 6 insertions, 18 deletions

diff --git a/gdb/testsuite/gdb.cp/except-multi-location.exp b/gdb/testsuite/gdb.cp/except-multi-location.exp
index 60d6d0b..1258d89 100644
--- a/gdb/testsuite/gdb.cp/except-multi-location.exp
+++ b/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}${ws}breakpoint${ws}keep${ws}y${ws}${hex}${ws}exception throw" \
-	     "${decimal}${ws}breakpoint${ws}keep${ws}y${ws}${hex}${ws}exception rethrow"]
+	     "${decimal}${ws}catchpoint${ws}keep${ws}y${ws}exception catch" \
+	     "${decimal}${ws}catchpoint${ws}keep${ws}y${ws}exception throw" \
+	     "${decimal}${ws}catchpoint${ws}keep${ws}y${ws}exception rethrow"]
 }
 
 # Try different static/not-static combinations.
diff --git a/gdb/testsuite/gdb.cp/exception.exp b/gdb/testsuite/gdb.cp/exception.exp
index 4761de2..0be382b 100644
--- a/gdb/testsuite/gdb.cp/exception.exp
+++ b/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${ws}exception catch"
-set re_3_bp	"2${ws}breakpoint${ws}keep${ws}y${ws}$addr${ws}exception throw"
-set re_4_bp   "3${ws}breakpoint${ws}keep${ws}y${ws}$addr${ws}exception rethrow"
+set re_2_bp	"1${ws}catchpoint${ws}keep${ws}y${ws}exception catch"
+set re_3_bp	"2${ws}catchpoint${ws}keep${ws}y${ws}exception throw"
+set re_4_bp	"3${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 $" {