[PATCH v2 8/8] Add $_ada_exception convenience variable

[Tom Tromey <tromey@adacore.com>]

This adds the $_ada_exception convenience variable.  It is set by the
Ada exception catchpoints, and holds the address of the exception
currently being thrown.  This is useful because it allows more
fine-grained filtering of exceptions than is possible using the
existing "catch" syntax.

This also simplifies Ada catchpoints somewhat; because the catchpoint
must now carry the "kind", it's possible to remove many helper
functions.

gdb/ChangeLog
2019-08-21  Tom Tromey  <tromey@adacore.com>

	* NEWS: Add $_ada_exception entry.
	* ada-lang.c (struct ada_catchpoint): Add constructor.
	<m_kind>: New member.
	(allocate_location_exception, re_set_exception): Remove
	"ex" parameter.
	(should_stop_exception): Compute $_ada_exception.
	(check_status_exception, print_it_exception)
	(print_one_exception, print_mention_exception): Remove
	"ex" parameter.
	(allocate_location_catch_exception, re_set_catch_exception)
	(check_status_exception, print_it_catch_exception)
	(print_one_catch_exception, print_mention_catch_exception)
	(print_recreate_catch_exception)
	(allocate_location_catch_exception_unhandled)
	(re_set_catch_exception_unhandled)
	(check_status_exception, print_it_catch_exception_unhandled)
	(print_one_catch_exception_unhandled)
	(print_mention_catch_exception_unhandled)
	(print_recreate_catch_exception_unhandled)
	(allocate_location_catch_assert, re_set_catch_assert)
	(check_status_assert, print_it_catch_assert)
	(print_one_catch_assert, print_mention_catch_assert)
	(print_recreate_catch_assert)
	(allocate_location_catch_handlers, re_set_catch_handlers)
	(check_status_handlers, print_it_catch_handlers)
	(print_one_catch_handlers, print_mention_catch_handlers)
	(print_recreate_catch_handlers): Remove.
	(create_ada_exception_catchpoint): Update.
	(initialize_ada_catchpoint_ops): Update.

gdb/doc/ChangeLog
2019-08-21  Tom Tromey  <tromey@adacore.com>

	* gdb.texinfo (Set Catchpoints, Convenience Vars): Document
	$_ada_exception.

gdb/testsuite/ChangeLog
2019-08-21  Tom Tromey  <tromey@adacore.com>

	* gdb.ada/catch_ex_std.exp: Add $_ada_exception test.
---
 gdb/ChangeLog                          |  32 +++
 gdb/NEWS                               |   3 +
 gdb/ada-lang.c                         | 307 +++++++------------------
 gdb/doc/ChangeLog                      |   5 +
 gdb/doc/gdb.texinfo                    |  20 +-
 gdb/testsuite/ChangeLog                |   4 +
 gdb/testsuite/gdb.ada/catch_ex_std.exp |   3 +
 7 files changed, 142 insertions(+), 232 deletions(-)

diff --git a/gdb/NEWS b/gdb/NEWS
index 1fefd814095..959ea27e749 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -34,6 +34,9 @@
 
 * GDB can now be compiled with Python 3 on Windows.
 
+* New convenience variable $_ada_exception holds the address of the
+  Ada exception being thrown.  This is set by Ada-related catchpoints.
+
 * Python API
 
   ** The gdb.Value type has a new method 'format_string' which returns a
diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index e4702b96876..1f388eb4dba 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -12326,8 +12326,16 @@ public:
 
 struct ada_catchpoint : public breakpoint
 {
+  explicit ada_catchpoint (enum ada_exception_catchpoint_kind kind)
+    : m_kind (kind)
+  {
+  }
+
   /* The name of the specific exception the user specified.  */
   std::string excep_string;
+
+  /* What kind of catchpoint this is.  */
+  enum ada_exception_catchpoint_kind m_kind;
 };
 
 /* Parse the exception condition string in the context of each of the
@@ -12387,8 +12395,7 @@ create_excep_cond_exprs (struct ada_catchpoint *c,
    structure for all exception catchpoint kinds.  */
 
 static struct bp_location *
-allocate_location_exception (enum ada_exception_catchpoint_kind ex,
-			     struct breakpoint *self)
+allocate_location_exception (struct breakpoint *self)
 {
   return new ada_catchpoint_location (self);
 }
@@ -12397,7 +12404,7 @@ allocate_location_exception (enum ada_exception_catchpoint_kind ex,
    exception catchpoint kinds.  */
 
 static void
-re_set_exception (enum ada_exception_catchpoint_kind ex, struct breakpoint *b)
+re_set_exception (struct breakpoint *b)
 {
   struct ada_catchpoint *c = (struct ada_catchpoint *) b;
 
@@ -12407,7 +12414,7 @@ re_set_exception (enum ada_exception_catchpoint_kind ex, struct breakpoint *b)
 
   /* Reparse the exception conditional expressions.  One for each
      location.  */
-  create_excep_cond_exprs (c, ex);
+  create_excep_cond_exprs (c, c->m_kind);
 }
 
 /* Returns true if we should stop for this breakpoint hit.  If the
@@ -12422,6 +12429,30 @@ should_stop_exception (const struct bp_location *bl)
     = (const struct ada_catchpoint_location *) bl;
   int stop;
 
+  struct internalvar *var = lookup_internalvar ("_ada_exception");
+  if (c->m_kind == ada_catch_assert)
+    clear_internalvar (var);
+  else
+    {
+      try
+	{
+	  const char *expr;
+
+	  if (c->m_kind == ada_catch_handlers)
+	    expr = ("GNAT_GCC_exception_Access(gcc_exception)"
+		    ".all.occurrence.id");
+	  else
+	    expr = "e";
+
+	  struct value *exc = parse_and_eval (expr);
+	  set_internalvar (var, exc);
+	}
+      catch (const gdb_exception_error &ex)
+	{
+	  clear_internalvar (var);
+	}
+    }
+
   /* With no specific exception, should always stop.  */
   if (c->excep_string.empty ())
     return 1;
@@ -12455,7 +12486,7 @@ should_stop_exception (const struct bp_location *bl)
    for all exception catchpoint kinds.  */
 
 static void
-check_status_exception (enum ada_exception_catchpoint_kind ex, bpstat bs)
+check_status_exception (bpstat bs)
 {
   bs->stop = should_stop_exception (bs->bp_location_at);
 }
@@ -12464,7 +12495,7 @@ check_status_exception (enum ada_exception_catchpoint_kind ex, bpstat bs)
    for all exception catchpoint kinds.  */
 
 static enum print_stop_action
-print_it_exception (enum ada_exception_catchpoint_kind ex, bpstat bs)
+print_it_exception (bpstat bs)
 {
   struct ui_out *uiout = current_uiout;
   struct breakpoint *b = bs->breakpoint_at;
@@ -12490,13 +12521,14 @@ print_it_exception (enum ada_exception_catchpoint_kind ex, bpstat bs)
      ada_find_printable_frame).  */
   select_frame (get_current_frame ());
 
-  switch (ex)
+  struct ada_catchpoint *c = (struct ada_catchpoint *) b;
+  switch (c->m_kind)
     {
       case ada_catch_exception:
       case ada_catch_exception_unhandled:
       case ada_catch_handlers:
 	{
-	  const CORE_ADDR addr = ada_exception_name_addr (ex, b);
+	  const CORE_ADDR addr = ada_exception_name_addr (c->m_kind, b);
 	  char exception_name[256];
 
 	  if (addr != 0)
@@ -12520,7 +12552,7 @@ print_it_exception (enum ada_exception_catchpoint_kind ex, bpstat bs)
 	     it clearer to the user which kind of catchpoint just got
 	     hit.  We used ui_out_text to make sure that this extra
 	     info does not pollute the exception name in the MI case.  */
-	  if (ex == ada_catch_exception_unhandled)
+	  if (c->m_kind == ada_catch_exception_unhandled)
 	    uiout->text ("unhandled ");
 	  uiout->field_string ("exception-name", exception_name);
 	}
@@ -12553,8 +12585,7 @@ print_it_exception (enum ada_exception_catchpoint_kind ex, bpstat bs)
    for all exception catchpoint kinds.  */
 
 static void
-print_one_exception (enum ada_exception_catchpoint_kind ex,
-                     struct breakpoint *b, struct bp_location **last_loc)
+print_one_exception (struct breakpoint *b, struct bp_location **last_loc)
 { 
   struct ui_out *uiout = current_uiout;
   struct ada_catchpoint *c = (struct ada_catchpoint *) b;
@@ -12566,7 +12597,7 @@ print_one_exception (enum ada_exception_catchpoint_kind ex,
     uiout->field_skip ("addr");
 
   annotate_field (5);
-  switch (ex)
+  switch (c->m_kind)
     {
       case ada_catch_exception:
         if (!c->excep_string.empty ())
@@ -12610,8 +12641,7 @@ print_one_exception (enum ada_exception_catchpoint_kind ex,
    for all exception catchpoint kinds.  */
 
 static void
-print_mention_exception (enum ada_exception_catchpoint_kind ex,
-                         struct breakpoint *b)
+print_mention_exception (struct breakpoint *b)
 {
   struct ada_catchpoint *c = (struct ada_catchpoint *) b;
   struct ui_out *uiout = current_uiout;
@@ -12621,7 +12651,7 @@ print_mention_exception (enum ada_exception_catchpoint_kind ex,
   uiout->field_signed ("bkptno", b->number);
   uiout->text (": ");
 
-  switch (ex)
+  switch (c->m_kind)
     {
       case ada_catch_exception:
         if (!c->excep_string.empty ())
@@ -12664,12 +12694,11 @@ print_mention_exception (enum ada_exception_catchpoint_kind ex,
    for all exception catchpoint kinds.  */
 
 static void
-print_recreate_exception (enum ada_exception_catchpoint_kind ex,
-			  struct breakpoint *b, struct ui_file *fp)
+print_recreate_exception (struct breakpoint *b, struct ui_file *fp)
 {
   struct ada_catchpoint *c = (struct ada_catchpoint *) b;
 
-  switch (ex)
+  switch (c->m_kind)
     {
       case ada_catch_exception:
 	fprintf_filtered (fp, "catch exception");
@@ -12695,192 +12724,10 @@ print_recreate_exception (enum ada_exception_catchpoint_kind ex,
   print_recreate_thread (b, fp);
 }
 
-/* Virtual table for "catch exception" breakpoints.  */
-
-static struct bp_location *
-allocate_location_catch_exception (struct breakpoint *self)
-{
-  return allocate_location_exception (ada_catch_exception, self);
-}
-
-static void
-re_set_catch_exception (struct breakpoint *b)
-{
-  re_set_exception (ada_catch_exception, b);
-}
-
-static void
-check_status_catch_exception (bpstat bs)
-{
-  check_status_exception (ada_catch_exception, bs);
-}
-
-static enum print_stop_action
-print_it_catch_exception (bpstat bs)
-{
-  return print_it_exception (ada_catch_exception, bs);
-}
-
-static void
-print_one_catch_exception (struct breakpoint *b, struct bp_location **last_loc)
-{
-  print_one_exception (ada_catch_exception, b, last_loc);
-}
-
-static void
-print_mention_catch_exception (struct breakpoint *b)
-{
-  print_mention_exception (ada_catch_exception, b);
-}
-
-static void
-print_recreate_catch_exception (struct breakpoint *b, struct ui_file *fp)
-{
-  print_recreate_exception (ada_catch_exception, b, fp);
-}
-
+/* Virtual tables for various breakpoint types.  */
 static struct breakpoint_ops catch_exception_breakpoint_ops;
-
-/* Virtual table for "catch exception unhandled" breakpoints.  */
-
-static struct bp_location *
-allocate_location_catch_exception_unhandled (struct breakpoint *self)
-{
-  return allocate_location_exception (ada_catch_exception_unhandled, self);
-}
-
-static void
-re_set_catch_exception_unhandled (struct breakpoint *b)
-{
-  re_set_exception (ada_catch_exception_unhandled, b);
-}
-
-static void
-check_status_catch_exception_unhandled (bpstat bs)
-{
-  check_status_exception (ada_catch_exception_unhandled, bs);
-}
-
-static enum print_stop_action
-print_it_catch_exception_unhandled (bpstat bs)
-{
-  return print_it_exception (ada_catch_exception_unhandled, bs);
-}
-
-static void
-print_one_catch_exception_unhandled (struct breakpoint *b,
-				     struct bp_location **last_loc)
-{
-  print_one_exception (ada_catch_exception_unhandled, b, last_loc);
-}
-
-static void
-print_mention_catch_exception_unhandled (struct breakpoint *b)
-{
-  print_mention_exception (ada_catch_exception_unhandled, b);
-}
-
-static void
-print_recreate_catch_exception_unhandled (struct breakpoint *b,
-					  struct ui_file *fp)
-{
-  print_recreate_exception (ada_catch_exception_unhandled, b, fp);
-}
-
 static struct breakpoint_ops catch_exception_unhandled_breakpoint_ops;
-
-/* Virtual table for "catch assert" breakpoints.  */
-
-static struct bp_location *
-allocate_location_catch_assert (struct breakpoint *self)
-{
-  return allocate_location_exception (ada_catch_assert, self);
-}
-
-static void
-re_set_catch_assert (struct breakpoint *b)
-{
-  re_set_exception (ada_catch_assert, b);
-}
-
-static void
-check_status_catch_assert (bpstat bs)
-{
-  check_status_exception (ada_catch_assert, bs);
-}
-
-static enum print_stop_action
-print_it_catch_assert (bpstat bs)
-{
-  return print_it_exception (ada_catch_assert, bs);
-}
-
-static void
-print_one_catch_assert (struct breakpoint *b, struct bp_location **last_loc)
-{
-  print_one_exception (ada_catch_assert, b, last_loc);
-}
-
-static void
-print_mention_catch_assert (struct breakpoint *b)
-{
-  print_mention_exception (ada_catch_assert, b);
-}
-
-static void
-print_recreate_catch_assert (struct breakpoint *b, struct ui_file *fp)
-{
-  print_recreate_exception (ada_catch_assert, b, fp);
-}
-
 static struct breakpoint_ops catch_assert_breakpoint_ops;
-
-/* Virtual table for "catch handlers" breakpoints.  */
-
-static struct bp_location *
-allocate_location_catch_handlers (struct breakpoint *self)
-{
-  return allocate_location_exception (ada_catch_handlers, self);
-}
-
-static void
-re_set_catch_handlers (struct breakpoint *b)
-{
-  re_set_exception (ada_catch_handlers, b);
-}
-
-static void
-check_status_catch_handlers (bpstat bs)
-{
-  check_status_exception (ada_catch_handlers, bs);
-}
-
-static enum print_stop_action
-print_it_catch_handlers (bpstat bs)
-{
-  return print_it_exception (ada_catch_handlers, bs);
-}
-
-static void
-print_one_catch_handlers (struct breakpoint *b,
-			  struct bp_location **last_loc)
-{
-  print_one_exception (ada_catch_handlers, b, last_loc);
-}
-
-static void
-print_mention_catch_handlers (struct breakpoint *b)
-{
-  print_mention_exception (ada_catch_handlers, b);
-}
-
-static void
-print_recreate_catch_handlers (struct breakpoint *b,
-			       struct ui_file *fp)
-{
-  print_recreate_exception (ada_catch_handlers, b, fp);
-}
-
 static struct breakpoint_ops catch_handlers_breakpoint_ops;
 
 /* See ada-lang.h.  */
@@ -13154,7 +13001,7 @@ create_ada_exception_catchpoint (struct gdbarch *gdbarch,
   const struct breakpoint_ops *ops = NULL;
   struct symtab_and_line sal = ada_exception_sal (ex_kind, &addr_string, &ops);
 
-  std::unique_ptr<ada_catchpoint> c (new ada_catchpoint ());
+  std::unique_ptr<ada_catchpoint> c (new ada_catchpoint (ex_kind));
   init_ada_exception_breakpoint (c.get (), gdbarch, sal, addr_string.c_str (),
 				 ops, tempflag, disabled, from_tty);
   c->excep_string = excep_string;
@@ -14345,43 +14192,43 @@ initialize_ada_catchpoint_ops (void)
 
   ops = &catch_exception_breakpoint_ops;
   *ops = bkpt_breakpoint_ops;
-  ops->allocate_location = allocate_location_catch_exception;
-  ops->re_set = re_set_catch_exception;
-  ops->check_status = check_status_catch_exception;
-  ops->print_it = print_it_catch_exception;
-  ops->print_one = print_one_catch_exception;
-  ops->print_mention = print_mention_catch_exception;
-  ops->print_recreate = print_recreate_catch_exception;
+  ops->allocate_location = allocate_location_exception;
+  ops->re_set = re_set_exception;
+  ops->check_status = check_status_exception;
+  ops->print_it = print_it_exception;
+  ops->print_one = print_one_exception;
+  ops->print_mention = print_mention_exception;
+  ops->print_recreate = print_recreate_exception;
 
   ops = &catch_exception_unhandled_breakpoint_ops;
   *ops = bkpt_breakpoint_ops;
-  ops->allocate_location = allocate_location_catch_exception_unhandled;
-  ops->re_set = re_set_catch_exception_unhandled;
-  ops->check_status = check_status_catch_exception_unhandled;
-  ops->print_it = print_it_catch_exception_unhandled;
-  ops->print_one = print_one_catch_exception_unhandled;
-  ops->print_mention = print_mention_catch_exception_unhandled;
-  ops->print_recreate = print_recreate_catch_exception_unhandled;
+  ops->allocate_location = allocate_location_exception;
+  ops->re_set = re_set_exception;
+  ops->check_status = check_status_exception;
+  ops->print_it = print_it_exception;
+  ops->print_one = print_one_exception;
+  ops->print_mention = print_mention_exception;
+  ops->print_recreate = print_recreate_exception;
 
   ops = &catch_assert_breakpoint_ops;
   *ops = bkpt_breakpoint_ops;
-  ops->allocate_location = allocate_location_catch_assert;
-  ops->re_set = re_set_catch_assert;
-  ops->check_status = check_status_catch_assert;
-  ops->print_it = print_it_catch_assert;
-  ops->print_one = print_one_catch_assert;
-  ops->print_mention = print_mention_catch_assert;
-  ops->print_recreate = print_recreate_catch_assert;
+  ops->allocate_location = allocate_location_exception;
+  ops->re_set = re_set_exception;
+  ops->check_status = check_status_exception;
+  ops->print_it = print_it_exception;
+  ops->print_one = print_one_exception;
+  ops->print_mention = print_mention_exception;
+  ops->print_recreate = print_recreate_exception;
 
   ops = &catch_handlers_breakpoint_ops;
   *ops = bkpt_breakpoint_ops;
-  ops->allocate_location = allocate_location_catch_handlers;
-  ops->re_set = re_set_catch_handlers;
-  ops->check_status = check_status_catch_handlers;
-  ops->print_it = print_it_catch_handlers;
-  ops->print_one = print_one_catch_handlers;
-  ops->print_mention = print_mention_catch_handlers;
-  ops->print_recreate = print_recreate_catch_handlers;
+  ops->allocate_location = allocate_location_exception;
+  ops->re_set = re_set_exception;
+  ops->check_status = check_status_exception;
+  ops->print_it = print_it_exception;
+  ops->print_one = print_one_exception;
+  ops->print_mention = print_mention_exception;
+  ops->print_recreate = print_recreate_exception;
 }
 
 /* This module's 'new_objfile' observer.  */
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index a129ea0aa1b..c3ed62002f8 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -4788,9 +4788,16 @@ called @code{Constraint_Error} is defined in package @code{Pck}, then
 the command to use to catch such exceptions is @kbd{catch exception
 Pck.Constraint_Error}.
 
+@vindex $_ada_exception@r{, convenience variable}
+The convenience variable @code{$_ada_exception} holds the address of
+the exception being thrown.  This can be useful when setting a
+condition for such a catchpoint.
+
 @item exception unhandled
 @kindex catch exception unhandled
-An exception that was raised but is not handled by the program.
+An exception that was raised but is not handled by the program.  The
+convenience variable @code{$_ada_exception} is set as for @code{catch
+exception}.
 
 @item handlers @r{[}@var{name}@r{]}
 @kindex catch handlers
@@ -4812,9 +4819,13 @@ user-defined one.  For instance, assuming an exception called
 command to use to catch such exceptions handling is
 @kbd{catch handlers Pck.Constraint_Error}.
 
+The convenience variable @code{$_ada_exception} is set as for
+@code{catch exception}.
+
 @item assert
 @kindex catch assert
-A failed Ada assertion.
+A failed Ada assertion.  Note that the convenience variable
+@code{$_ada_exception} is @emph{not} set by this catchpoint.
 
 @item exec
 @kindex catch exec
@@ -11823,6 +11834,11 @@ The program has exited
 The variable @code{$_exception} is set to the exception object being
 thrown at an exception-related catchpoint.  @xref{Set Catchpoints}.
 
+@item $_ada_exception
+The variable @code{$_ada_exception} is set to the address of the
+exception being caught or thrown at an Ada exception-related
+catchpoint.  @xref{Set Catchpoints}.
+
 @item $_probe_argc
 @itemx $_probe_arg0@dots{}$_probe_arg11
 Arguments to a static probe.  @xref{Static Probe Points}.
diff --git a/gdb/testsuite/gdb.ada/catch_ex_std.exp b/gdb/testsuite/gdb.ada/catch_ex_std.exp
index 63714a8aa81..839d0bb092f 100644
--- a/gdb/testsuite/gdb.ada/catch_ex_std.exp
+++ b/gdb/testsuite/gdb.ada/catch_ex_std.exp
@@ -101,3 +101,6 @@ gdb_test "catch exception some_kind_of_error" \
 gdb_test "cont" \
     "Catchpoint \[0-9\]+, .* at .*foo\.adb:\[0-9\]+.*" \
     "caught the exception"
+
+gdb_test "print \$_ada_exception = some_package.some_kind_of_error'Address" \
+    " = true"
-- 
2.20.1