gdb/break-catch-throw.c - binutils-gdb - Git at Google

 /* Everything about catch/throw catchpoints, for GDB.

    Copyright (C) 1986-2024 Free Software Foundation, Inc.

    This file is part of GDB.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

 #include "arch-utils.h"
 #include <ctype.h>
 #include "breakpoint.h"
 #include "exceptions.h"
 #include "inferior.h"
 #include "annotate.h"
 #include "valprint.h"
 #include "cli/cli-utils.h"
 #include "completer.h"
 #include "gdbsupport/gdb_obstack.h"
 #include "mi/mi-common.h"
 #include "linespec.h"
 #include "probe.h"
 #include "objfiles.h"
 #include "cp-abi.h"
 #include "gdbsupport/gdb_regex.h"
 #include "cp-support.h"
 #include "location.h"
 #include "cli/cli-decode.h"

 /* Each spot where we may place an exception-related catchpoint has
    two names: the SDT probe point and the function name.  This
    structure holds both.  */

 struct exception_names
 {
   /* The name of the probe point to try, in the form accepted by
      'parse_probes'.  */

   const char *probe;

   /* The name of the corresponding function.  */

   const char *function;
 };

 /* Names of the probe points and functions on which to break.  This is
    indexed by exception_event_kind.  */
 static const struct exception_names exception_functions[] =
 {
   { "-probe-stap libstdcxx:throw", "__cxa_throw" },
   { "-probe-stap libstdcxx:rethrow", "__cxa_rethrow" },
   { "-probe-stap libstdcxx:catch", "__cxa_begin_catch" }
 };

 /* The type of an exception catchpoint.  Unlike most catchpoints, this
    one is implemented with code breakpoints, so it inherits struct
    code_breakpoint, not struct catchpoint.  */

 struct exception_catchpoint : public code_breakpoint
 {
   exception_catchpoint (struct gdbarch *gdbarch,
 			bool temp, const char *cond_string_,
 			enum exception_event_kind kind_,
 			std::string &&except_rx)
     : code_breakpoint (gdbarch, bp_catchpoint, temp, cond_string_),
       kind (kind_),
       exception_rx (std::move (except_rx)),
       pattern (exception_rx.empty ()
 	       ? nullptr
 	       : new compiled_regex (exception_rx.c_str (), REG_NOSUB,
 				     _("invalid type-matching regexp")))
   {
     pspace = current_program_space;
     re_set ();
   }

   void re_set () override;
   enum print_stop_action print_it (const bpstat *bs) const override;
   bool print_one (const bp_location **) const override;
   void print_mention () const override;
   void print_recreate (struct ui_file *fp) const override;
   void print_one_detail (struct ui_out *) const override;
   void check_status (struct bpstat *bs) override;
   struct bp_location *allocate_location () override;

   /* The kind of exception catchpoint.  */

   enum exception_event_kind kind;

   /* If not empty, a string holding the source form of the regular
      expression to match against.  */

   std::string exception_rx;

   /* If non-NULL, a compiled regular expression which is used to
      determine which exceptions to stop on.  */

   std::unique_ptr<compiled_regex> pattern;
 };

 /* See breakpoint.h.  */

 bool
 is_exception_catchpoint (breakpoint *bp)
 {
   return dynamic_cast<exception_catchpoint *> (bp) != nullptr;
 }


 /* A helper function that fetches exception probe arguments.  This
    fills in *ARG0 (if non-NULL) and *ARG1 (which must be non-NULL).
    It will throw an exception on any kind of failure.  */

 static void
 fetch_probe_arguments (struct value **arg0, struct value **arg1)
 {
   frame_info_ptr frame = get_selected_frame (_("No frame selected"));
   CORE_ADDR pc = get_frame_pc (frame);
   struct bound_probe pc_probe;
   unsigned n_args;

   pc_probe = find_probe_by_pc (pc);
   if (pc_probe.prob == NULL)
     error (_("did not find exception probe (does libstdcxx have SDT probes?)"));

   if (pc_probe.prob->get_provider () != "libstdcxx"
       || (pc_probe.prob->get_name () != "catch"
 	  && pc_probe.prob->get_name () != "throw"
 	  && pc_probe.prob->get_name () != "rethrow"))
     error (_("not stopped at a C++ exception catchpoint"));

   n_args = pc_probe.prob->get_argument_count (get_frame_arch (frame));
   if (n_args < 2)
     error (_("C++ exception catchpoint has too few arguments"));

   if (arg0 != NULL)
     *arg0 = pc_probe.prob->evaluate_argument (0, frame);
   *arg1 = pc_probe.prob->evaluate_argument (1, frame);

   if ((arg0 != NULL && *arg0 == NULL) || *arg1 == NULL)
     error (_("error computing probe argument at c++ exception catchpoint"));
 }


 /* Implement the 'check_status' method.  */

 void
 exception_catchpoint::check_status (struct bpstat *bs)
 {
   std::string type_name;

   this->breakpoint::check_status (bs);
   if (!bs->stop)
     return;

   if (this->pattern == NULL)
     return;

   const char *name = nullptr;
   gdb::unique_xmalloc_ptr<char> canon;
   try
     {
       struct value *typeinfo_arg;

       fetch_probe_arguments (NULL, &typeinfo_arg);
       type_name = cplus_typename_from_type_info (typeinfo_arg);

       canon = cp_canonicalize_string (type_name.c_str ());
       name = (canon != nullptr
 	      ? canon.get ()
 	      : type_name.c_str ());
     }
   catch (const gdb_exception_error &e)
     {
       exception_print (gdb_stderr, e);
     }

   if (name != nullptr)
     {
       if (this->pattern->exec (name, 0, NULL, 0) != 0)
 	bs->stop = false;
     }
 }

 /* Implement the 're_set' method.  */

 void
 exception_catchpoint::re_set ()
 {
   std::vector<symtab_and_line> sals;
   struct program_space *filter_pspace = current_program_space;

   /* We first try to use the probe interface.  */
   try
     {
       location_spec_up locspec
 	= new_probe_location_spec (exception_functions[kind].probe);
       sals = parse_probes (locspec.get (), filter_pspace, NULL);
     }
   catch (const gdb_exception_error &e)
     {
       /* Using the probe interface failed.  Let's fallback to the normal
 	 catchpoint mode.  */
       try
 	{
 	  location_spec_up locspec
 	    = (new_explicit_location_spec_function
 	       (exception_functions[kind].function));
 	  sals = this->decode_location_spec (locspec.get (), filter_pspace);
 	}
       catch (const gdb_exception_error &ex)
 	{
 	  /* NOT_FOUND_ERROR just means the breakpoint will be
 	     pending, so let it through.  */
 	  if (ex.error != NOT_FOUND_ERROR)
 	    throw;
 	}
     }

   update_breakpoint_locations (this, filter_pspace, sals, {});
 }

 enum print_stop_action
 exception_catchpoint::print_it (const bpstat *bs) const
 {
   struct ui_out *uiout = current_uiout;
   int bp_temp;

   annotate_catchpoint (number);
   maybe_print_thread_hit_breakpoint (uiout);

   bp_temp = disposition == disp_del;
   uiout->text (bp_temp ? "Temporary catchpoint "
 		       : "Catchpoint ");
   print_num_locno (bs, uiout);
   uiout->text ((kind == EX_EVENT_THROW ? " (exception thrown), "
 		: (kind == EX_EVENT_CATCH ? " (exception caught), "
 		   : " (exception rethrown), ")));
   if (uiout->is_mi_like_p ())
     {
       uiout->field_string ("reason",
 			   async_reason_lookup (EXEC_ASYNC_BREAKPOINT_HIT));
       uiout->field_string ("disp", bpdisp_text (disposition));
     }
   return PRINT_SRC_AND_LOC;
 }

 bool
 exception_catchpoint::print_one (const bp_location **last_loc) const
 {
   struct value_print_options opts;
   struct ui_out *uiout = current_uiout;

   get_user_print_options (&opts);

   if (opts.addressprint)
     uiout->field_skip ("addr");
   annotate_field (5);

   switch (kind)
     {
     case EX_EVENT_THROW:
       uiout->field_string ("what", "exception throw");
       if (uiout->is_mi_like_p ())
 	uiout->field_string ("catch-type", "throw");
       break;

     case EX_EVENT_RETHROW:
       uiout->field_string ("what", "exception rethrow");
       if (uiout->is_mi_like_p ())
 	uiout->field_string ("catch-type", "rethrow");
       break;

     case EX_EVENT_CATCH:
       uiout->field_string ("what", "exception catch");
       if (uiout->is_mi_like_p ())
 	uiout->field_string ("catch-type", "catch");
       break;
     }

   return true;
 }

 /* Implement the 'print_one_detail' method.  */

 void
 exception_catchpoint::print_one_detail (struct ui_out *uiout) const
 {
   if (!exception_rx.empty ())
     {
       uiout->text (_("\tmatching: "));
       uiout->field_string ("regexp", exception_rx);
       uiout->text ("\n");
     }
 }

 void
 exception_catchpoint::print_mention () const
 {
   struct ui_out *uiout = current_uiout;
   int bp_temp;

   bp_temp = disposition == disp_del;
   uiout->message ("%s %d %s",
 		  (bp_temp ? _("Temporary catchpoint ") : _("Catchpoint")),
 		  number,
 		  (kind == EX_EVENT_THROW
 		   ? _("(throw)") : (kind == EX_EVENT_CATCH
 				     ? _("(catch)") : _("(rethrow)"))));
 }

 /* Implement the "print_recreate" method for throw and catch
    catchpoints.  */

 void
 exception_catchpoint::print_recreate (struct ui_file *fp) const
 {
   int bp_temp;

   bp_temp = disposition == disp_del;
   gdb_printf (fp, bp_temp ? "tcatch " : "catch ");
   switch (kind)
     {
     case EX_EVENT_THROW:
       gdb_printf (fp, "throw");
       break;
     case EX_EVENT_CATCH:
       gdb_printf (fp, "catch");
       break;
     case EX_EVENT_RETHROW:
       gdb_printf (fp, "rethrow");
       break;
     }
   print_recreate_thread (fp);
 }

 /* Implement the "allocate_location" method for throw and catch
    catchpoints.  */

 bp_location *
 exception_catchpoint::allocate_location ()
 {
   return new bp_location (this, bp_loc_software_breakpoint);
 }

 static void
 handle_gnu_v3_exceptions (int tempflag, std::string &&except_rx,
 			  const char *cond_string,
 			  enum exception_event_kind ex_event, int from_tty)
 {
   struct gdbarch *gdbarch = get_current_arch ();

   std::unique_ptr<exception_catchpoint> cp
     (new exception_catchpoint (gdbarch, tempflag, cond_string,
 			       ex_event, std::move (except_rx)));

   install_breakpoint (0, std::move (cp), 1);
 }

 /* Look for an "if" token in *STRING.  The "if" token must be preceded
    by whitespace.

    If there is any non-whitespace text between *STRING and the "if"
    token, then it is returned in a newly-xmalloc'd string.  Otherwise,
    this returns NULL.

    STRING is updated to point to the "if" token, if it exists, or to
    the end of the string.  */

 static std::string
 extract_exception_regexp (const char **string)
 {
   const char *start;
   const char *last, *last_space;

   start = skip_spaces (*string);

   last = start;
   last_space = start;
   while (*last != '\0')
     {
       const char *if_token = last;

       /* Check for the "if".  */
       if (check_for_argument (&if_token, "if", 2))
 	break;

       /* No "if" token here.  Skip to the next word start.  */
       last_space = skip_to_space (last);
       last = skip_spaces (last_space);
     }

   *string = last;
   if (last_space > start)
     return std::string (start, last_space - start);
   return std::string ();
 }

 /* See breakpoint.h.  */

 void
 catch_exception_event (enum exception_event_kind ex_event,
 		       const char *arg, bool tempflag, int from_tty)
 {
   const char *cond_string = NULL;

   if (!arg)
     arg = "";
   arg = skip_spaces (arg);

   std::string except_rx = extract_exception_regexp (&arg);

   cond_string = ep_parse_optional_if_clause (&arg);

   if ((*arg != '\0') && !isspace (*arg))
     error (_("Junk at end of arguments."));

   if (ex_event != EX_EVENT_THROW
       && ex_event != EX_EVENT_CATCH
       && ex_event != EX_EVENT_RETHROW)
     error (_("Unsupported or unknown exception event; cannot catch it"));

   handle_gnu_v3_exceptions (tempflag, std::move (except_rx), cond_string,
 			    ex_event, from_tty);
 }

 /* Implementation of "catch catch" command.  */

 static void
 catch_catch_command (const char *arg, int from_tty,
 		     struct cmd_list_element *command)
 {
   bool tempflag = command->context () == CATCH_TEMPORARY;

   catch_exception_event (EX_EVENT_CATCH, arg, tempflag, from_tty);
 }

 /* Implementation of "catch throw" command.  */

 static void
 catch_throw_command (const char *arg, int from_tty,
 		     struct cmd_list_element *command)
 {
   bool tempflag = command->context () == CATCH_TEMPORARY;

   catch_exception_event (EX_EVENT_THROW, arg, tempflag, from_tty);
 }

 /* Implementation of "catch rethrow" command.  */

 static void
 catch_rethrow_command (const char *arg, int from_tty,
 		       struct cmd_list_element *command)
 {
   bool tempflag = command->context () == CATCH_TEMPORARY;

   catch_exception_event (EX_EVENT_RETHROW, arg, tempflag, from_tty);
 }


 /* Implement the 'make_value' method for the $_exception
    internalvar.  */

 static struct value *
 compute_exception (struct gdbarch *argc, struct internalvar *var, void *ignore)
 {
   struct value *arg0, *arg1;
   struct type *obj_type;

   fetch_probe_arguments (&arg0, &arg1);

   /* ARG0 is a pointer to the exception object.  ARG1 is a pointer to
      the std::type_info for the exception.  Now we find the type from
      the type_info and cast the result.  */
   obj_type = cplus_type_from_type_info (arg1);
   return value_ind (value_cast (make_pointer_type (obj_type, NULL), arg0));
 }

 /* Implementation of the '$_exception' variable.  */

 static const struct internalvar_funcs exception_funcs =
 {
   compute_exception,
   NULL,
 };


 void _initialize_break_catch_throw ();
 void
 _initialize_break_catch_throw ()
 {
   /* Add catch and tcatch sub-commands.  */
   add_catch_command ("catch", _("\
 Catch an exception, when caught."),
 		     catch_catch_command,
 		     NULL,
 		     CATCH_PERMANENT,
 		     CATCH_TEMPORARY);
   add_catch_command ("throw", _("\
 Catch an exception, when thrown."),
 		     catch_throw_command,
 		     NULL,
 		     CATCH_PERMANENT,
 		     CATCH_TEMPORARY);
   add_catch_command ("rethrow", _("\
 Catch an exception, when rethrown."),
 		     catch_rethrow_command,
 		     NULL,
 		     CATCH_PERMANENT,
 		     CATCH_TEMPORARY);

   create_internalvar_type_lazy ("_exception", &exception_funcs, NULL);
 }
	/* Everything about catch/throw catchpoints, for GDB.

	Copyright (C) 1986-2024 Free Software Foundation, Inc.

	This file is part of GDB.

	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 3 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program. If not, see <http://www.gnu.org/licenses/>. */

	#include "arch-utils.h"
	#include <ctype.h>
	#include "breakpoint.h"
	#include "exceptions.h"
	#include "inferior.h"
	#include "annotate.h"
	#include "valprint.h"
	#include "cli/cli-utils.h"
	#include "completer.h"
	#include "gdbsupport/gdb_obstack.h"
	#include "mi/mi-common.h"
	#include "linespec.h"
	#include "probe.h"
	#include "objfiles.h"
	#include "cp-abi.h"
	#include "gdbsupport/gdb_regex.h"
	#include "cp-support.h"
	#include "location.h"
	#include "cli/cli-decode.h"

	/* Each spot where we may place an exception-related catchpoint has
	two names: the SDT probe point and the function name. This
	structure holds both. */

	struct exception_names
	{
	/* The name of the probe point to try, in the form accepted by
	'parse_probes'. */

	const char *probe;

	/* The name of the corresponding function. */

	const char *function;
	};

	/* Names of the probe points and functions on which to break. This is
	indexed by exception_event_kind. */
	static const struct exception_names exception_functions[] =
	{
	{ "-probe-stap libstdcxx:throw", "__cxa_throw" },
	{ "-probe-stap libstdcxx:rethrow", "__cxa_rethrow" },
	{ "-probe-stap libstdcxx:catch", "__cxa_begin_catch" }
	};

	/* The type of an exception catchpoint. Unlike most catchpoints, this
	one is implemented with code breakpoints, so it inherits struct
	code_breakpoint, not struct catchpoint. */

	struct exception_catchpoint : public code_breakpoint
	{
	exception_catchpoint (struct gdbarch *gdbarch,
	bool temp, const char *cond_string_,
	enum exception_event_kind kind_,
	std::string &&except_rx)
	: code_breakpoint (gdbarch, bp_catchpoint, temp, cond_string_),
	kind (kind_),
	exception_rx (std::move (except_rx)),
	pattern (exception_rx.empty ()
	? nullptr
	: new compiled_regex (exception_rx.c_str (), REG_NOSUB,
	_("invalid type-matching regexp")))
	{
	pspace = current_program_space;
	re_set ();
	}

	void re_set () override;
	enum print_stop_action print_it (const bpstat *bs) const override;
	bool print_one (const bp_location **) const override;
	void print_mention () const override;
	void print_recreate (struct ui_file *fp) const override;
	void print_one_detail (struct ui_out *) const override;
	void check_status (struct bpstat *bs) override;
	struct bp_location *allocate_location () override;

	/* The kind of exception catchpoint. */

	enum exception_event_kind kind;

	/* If not empty, a string holding the source form of the regular
	expression to match against. */

	std::string exception_rx;

	/* If non-NULL, a compiled regular expression which is used to
	determine which exceptions to stop on. */

	std::unique_ptr<compiled_regex> pattern;
	};

	/* See breakpoint.h. */

	bool
	is_exception_catchpoint (breakpoint *bp)
	{
	return dynamic_cast<exception_catchpoint *> (bp) != nullptr;
	}



	/* A helper function that fetches exception probe arguments. This
	fills in ARG0 (if non-NULL) and ARG1 (which must be non-NULL).
	It will throw an exception on any kind of failure. */

	static void
	fetch_probe_arguments (struct value arg0, struct value arg1)
	{
	frame_info_ptr frame = get_selected_frame (_("No frame selected"));
	CORE_ADDR pc = get_frame_pc (frame);
	struct bound_probe pc_probe;
	unsigned n_args;

	pc_probe = find_probe_by_pc (pc);
	if (pc_probe.prob == NULL)
	error (_("did not find exception probe (does libstdcxx have SDT probes?)"));

	if (pc_probe.prob->get_provider () != "libstdcxx"
	\|\| (pc_probe.prob->get_name () != "catch"
	&& pc_probe.prob->get_name () != "throw"
	&& pc_probe.prob->get_name () != "rethrow"))
	error (_("not stopped at a C++ exception catchpoint"));

	n_args = pc_probe.prob->get_argument_count (get_frame_arch (frame));
	if (n_args < 2)
	error (_("C++ exception catchpoint has too few arguments"));

	if (arg0 != NULL)
	*arg0 = pc_probe.prob->evaluate_argument (0, frame);
	*arg1 = pc_probe.prob->evaluate_argument (1, frame);

	if ((arg0 != NULL && arg0 == NULL) \|\| arg1 == NULL)
	error (_("error computing probe argument at c++ exception catchpoint"));
	}



	/* Implement the 'check_status' method. */

	void
	exception_catchpoint::check_status (struct bpstat *bs)
	{
	std::string type_name;

	this->breakpoint::check_status (bs);
	if (!bs->stop)
	return;

	if (this->pattern == NULL)
	return;

	const char *name = nullptr;
	gdb::unique_xmalloc_ptr<char> canon;
	try
	{
	struct value *typeinfo_arg;

	fetch_probe_arguments (NULL, &typeinfo_arg);
	type_name = cplus_typename_from_type_info (typeinfo_arg);

	canon = cp_canonicalize_string (type_name.c_str ());
	name = (canon != nullptr
	? canon.get ()
	: type_name.c_str ());
	}
	catch (const gdb_exception_error &e)
	{
	exception_print (gdb_stderr, e);
	}

	if (name != nullptr)
	{
	if (this->pattern->exec (name, 0, NULL, 0) != 0)
	bs->stop = false;
	}
	}

	/* Implement the 're_set' method. */

	void
	exception_catchpoint::re_set ()
	{
	std::vector<symtab_and_line> sals;
	struct program_space *filter_pspace = current_program_space;

	/* We first try to use the probe interface. */
	try
	{
	location_spec_up locspec
	= new_probe_location_spec (exception_functions[kind].probe);
	sals = parse_probes (locspec.get (), filter_pspace, NULL);
	}
	catch (const gdb_exception_error &e)
	{
	/* Using the probe interface failed. Let's fallback to the normal
	catchpoint mode. */
	try
	{
	location_spec_up locspec
	= (new_explicit_location_spec_function
	(exception_functions[kind].function));
	sals = this->decode_location_spec (locspec.get (), filter_pspace);
	}
	catch (const gdb_exception_error &ex)
	{
	/* NOT_FOUND_ERROR just means the breakpoint will be
	pending, so let it through. */
	if (ex.error != NOT_FOUND_ERROR)
	throw;
	}
	}

	update_breakpoint_locations (this, filter_pspace, sals, {});
	}

	enum print_stop_action
	exception_catchpoint::print_it (const bpstat *bs) const
	{
	struct ui_out *uiout = current_uiout;
	int bp_temp;

	annotate_catchpoint (number);
	maybe_print_thread_hit_breakpoint (uiout);

	bp_temp = disposition == disp_del;
	uiout->text (bp_temp ? "Temporary catchpoint "
	: "Catchpoint ");
	print_num_locno (bs, uiout);
	uiout->text ((kind == EX_EVENT_THROW ? " (exception thrown), "
	: (kind == EX_EVENT_CATCH ? " (exception caught), "
	: " (exception rethrown), ")));
	if (uiout->is_mi_like_p ())
	{
	uiout->field_string ("reason",
	async_reason_lookup (EXEC_ASYNC_BREAKPOINT_HIT));
	uiout->field_string ("disp", bpdisp_text (disposition));
	}
	return PRINT_SRC_AND_LOC;
	}

	bool
	exception_catchpoint::print_one (const bp_location **last_loc) const
	{
	struct value_print_options opts;
	struct ui_out *uiout = current_uiout;

	get_user_print_options (&opts);

	if (opts.addressprint)
	uiout->field_skip ("addr");
	annotate_field (5);

	switch (kind)
	{
	case EX_EVENT_THROW:
	uiout->field_string ("what", "exception throw");
	if (uiout->is_mi_like_p ())
	uiout->field_string ("catch-type", "throw");
	break;

	case EX_EVENT_RETHROW:
	uiout->field_string ("what", "exception rethrow");
	if (uiout->is_mi_like_p ())
	uiout->field_string ("catch-type", "rethrow");
	break;

	case EX_EVENT_CATCH:
	uiout->field_string ("what", "exception catch");
	if (uiout->is_mi_like_p ())
	uiout->field_string ("catch-type", "catch");
	break;
	}

	return true;
	}

	/* Implement the 'print_one_detail' method. */

	void
	exception_catchpoint::print_one_detail (struct ui_out *uiout) const
	{
	if (!exception_rx.empty ())
	{
	uiout->text (_("\tmatching: "));
	uiout->field_string ("regexp", exception_rx);
	uiout->text ("\n");
	}
	}

	void
	exception_catchpoint::print_mention () const
	{
	struct ui_out *uiout = current_uiout;
	int bp_temp;

	bp_temp = disposition == disp_del;
	uiout->message ("%s %d %s",
	(bp_temp ? _("Temporary catchpoint ") : _("Catchpoint")),
	number,
	(kind == EX_EVENT_THROW
	? _("(throw)") : (kind == EX_EVENT_CATCH
	? _("(catch)") : _("(rethrow)"))));
	}

	/* Implement the "print_recreate" method for throw and catch
	catchpoints. */

	void
	exception_catchpoint::print_recreate (struct ui_file *fp) const
	{
	int bp_temp;

	bp_temp = disposition == disp_del;
	gdb_printf (fp, bp_temp ? "tcatch " : "catch ");
	switch (kind)
	{
	case EX_EVENT_THROW:
	gdb_printf (fp, "throw");
	break;
	case EX_EVENT_CATCH:
	gdb_printf (fp, "catch");
	break;
	case EX_EVENT_RETHROW:
	gdb_printf (fp, "rethrow");
	break;
	}
	print_recreate_thread (fp);
	}

	/* Implement the "allocate_location" method for throw and catch
	catchpoints. */

	bp_location *
	exception_catchpoint::allocate_location ()
	{
	return new bp_location (this, bp_loc_software_breakpoint);
	}

	static void
	handle_gnu_v3_exceptions (int tempflag, std::string &&except_rx,
	const char *cond_string,
	enum exception_event_kind ex_event, int from_tty)
	{
	struct gdbarch *gdbarch = get_current_arch ();

	std::unique_ptr<exception_catchpoint> cp
	(new exception_catchpoint (gdbarch, tempflag, cond_string,
	ex_event, std::move (except_rx)));

	install_breakpoint (0, std::move (cp), 1);
	}

	/* Look for an "if" token in *STRING. The "if" token must be preceded
	by whitespace.

	If there is any non-whitespace text between *STRING and the "if"
	token, then it is returned in a newly-xmalloc'd string. Otherwise,
	this returns NULL.

	STRING is updated to point to the "if" token, if it exists, or to
	the end of the string. */

	static std::string
	extract_exception_regexp (const char **string)
	{
	const char *start;
	const char last, last_space;

	start = skip_spaces (*string);

	last = start;
	last_space = start;
	while (*last != '\0')
	{
	const char *if_token = last;

	/* Check for the "if". */
	if (check_for_argument (&if_token, "if", 2))
	break;

	/* No "if" token here. Skip to the next word start. */
	last_space = skip_to_space (last);
	last = skip_spaces (last_space);
	}

	*string = last;
	if (last_space > start)
	return std::string (start, last_space - start);
	return std::string ();
	}

	/* See breakpoint.h. */

	void
	catch_exception_event (enum exception_event_kind ex_event,
	const char *arg, bool tempflag, int from_tty)
	{
	const char *cond_string = NULL;

	if (!arg)
	arg = "";
	arg = skip_spaces (arg);

	std::string except_rx = extract_exception_regexp (&arg);

	cond_string = ep_parse_optional_if_clause (&arg);

	if ((arg != '\0') && !isspace (arg))
	error (_("Junk at end of arguments."));

	if (ex_event != EX_EVENT_THROW
	&& ex_event != EX_EVENT_CATCH
	&& ex_event != EX_EVENT_RETHROW)
	error (_("Unsupported or unknown exception event; cannot catch it"));

	handle_gnu_v3_exceptions (tempflag, std::move (except_rx), cond_string,
	ex_event, from_tty);
	}

	/* Implementation of "catch catch" command. */

	static void
	catch_catch_command (const char *arg, int from_tty,
	struct cmd_list_element *command)
	{
	bool tempflag = command->context () == CATCH_TEMPORARY;

	catch_exception_event (EX_EVENT_CATCH, arg, tempflag, from_tty);
	}

	/* Implementation of "catch throw" command. */

	static void
	catch_throw_command (const char *arg, int from_tty,
	struct cmd_list_element *command)
	{
	bool tempflag = command->context () == CATCH_TEMPORARY;

	catch_exception_event (EX_EVENT_THROW, arg, tempflag, from_tty);
	}

	/* Implementation of "catch rethrow" command. */

	static void
	catch_rethrow_command (const char *arg, int from_tty,
	struct cmd_list_element *command)
	{
	bool tempflag = command->context () == CATCH_TEMPORARY;

	catch_exception_event (EX_EVENT_RETHROW, arg, tempflag, from_tty);
	}



	/* Implement the 'make_value' method for the $_exception
	internalvar. */

	static struct value *
	compute_exception (struct gdbarch argc, struct internalvar var, void *ignore)
	{
	struct value arg0, arg1;
	struct type *obj_type;

	fetch_probe_arguments (&arg0, &arg1);

	/* ARG0 is a pointer to the exception object. ARG1 is a pointer to
	the std::type_info for the exception. Now we find the type from
	the type_info and cast the result. */
	obj_type = cplus_type_from_type_info (arg1);
	return value_ind (value_cast (make_pointer_type (obj_type, NULL), arg0));
	}

	/* Implementation of the '$_exception' variable. */

	static const struct internalvar_funcs exception_funcs =
	{
	compute_exception,
	NULL,
	};



	void _initialize_break_catch_throw ();
	void
	_initialize_break_catch_throw ()
	{
	/* Add catch and tcatch sub-commands. */
	add_catch_command ("catch", _("\
	Catch an exception, when caught."),
	catch_catch_command,
	NULL,
	CATCH_PERMANENT,
	CATCH_TEMPORARY);
	add_catch_command ("throw", _("\
	Catch an exception, when thrown."),
	catch_throw_command,
	NULL,
	CATCH_PERMANENT,
	CATCH_TEMPORARY);
	add_catch_command ("rethrow", _("\
	Catch an exception, when rethrown."),
	catch_rethrow_command,
	NULL,
	CATCH_PERMANENT,
	CATCH_TEMPORARY);

	create_internalvar_type_lazy ("_exception", &exception_funcs, NULL);
	}