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binutils-gdb/gdb/cli/cli-interp.c
Pedro Alves 492d29ea1c Split TRY_CATCH into TRY + CATCH 
This patch splits the TRY_CATCH macro into three, so that we go from
this:

~~~
  volatile gdb_exception ex;

  TRY_CATCH (ex, RETURN_MASK_ERROR)
    {
    }
  if (ex.reason < 0)
    {
    }
~~~

to this:

~~~
  TRY
    {
    }
  CATCH (ex, RETURN_MASK_ERROR)
    {
    }
  END_CATCH
~~~

Thus, we'll be getting rid of the local volatile exception object, and
declaring the caught exception in the catch block.

This allows reimplementing TRY/CATCH in terms of C++ exceptions when
building in C++ mode, while still allowing to build GDB in C mode
(using setjmp/longjmp), as a transition step.

TBC, after this patch, is it _not_ valid to have code between the TRY
and the CATCH blocks, like:

  TRY
    {
    }

  // some code here.

  CATCH (ex, RETURN_MASK_ERROR)
    {
    }
  END_CATCH

Just like it isn't valid to do that with C++'s native try/catch.

By switching to creating the exception object inside the CATCH block
scope, we can get rid of all the explicitly allocated volatile
exception objects all over the tree, and map the CATCH block more
directly to C++'s catch blocks.

The majority of the TRY_CATCH -> TRY+CATCH+END_CATCH conversion was
done with a script, rerun from scratch at every rebase, no manual
editing involved.  After the mechanical conversion, a few places
needed manual intervention, to fix preexisting cases where we were
using the exception object outside of the TRY_CATCH block, and cases
where we were using "else" after a 'if (ex.reason) < 0)' [a CATCH
after this patch].  The result was folded into this patch so that GDB
still builds at each incremental step.

END_CATCH is necessary for two reasons:

First, because we name the exception object in the CATCH block, which
requires creating a scope, which in turn must be closed somewhere.
Declaring the exception variable in the initializer field of a for
block, like:

  #define CATCH(EXCEPTION, mask) \
    for (struct gdb_exception EXCEPTION; \
         exceptions_state_mc_catch (&EXCEPTION, MASK); \
	 EXCEPTION = exception_none)

would avoid needing END_CATCH, but alas, in C mode, we build with C90,
which doesn't allow mixed declarations and code.

Second, because when TRY/CATCH are wired to real C++ try/catch, as
long as we need to handle cleanup chains, even if there's no CATCH
block that wants to catch the exception, we need for stop at every
frame in the unwind chain and run cleanups, then rethrow.  That will
be done in END_CATCH.

After we require C++, we'll still need TRY/CATCH/END_CATCH until
cleanups are completely phased out -- TRY/CATCH in C++ mode will
save/restore the current cleanup chain, like in C mode, and END_CATCH
catches otherwise uncaugh exceptions, runs cleanups and rethrows, so
that C++ cleanups and exceptions can coexist.

IMO, this still makes the TRY/CATCH code look a bit more like a
newcomer would expect, so IMO worth it even if we weren't considering
C++.

gdb/ChangeLog.
2015-03-07  Pedro Alves  <palves@redhat.com>

	* common/common-exceptions.c (struct catcher) <exception>: No
	longer a pointer to volatile exception.  Now an exception value.
	<mask>: Delete field.
	(exceptions_state_mc_init): Remove all parameters.  Adjust.
	(exceptions_state_mc): No longer pop the catcher here.
	(exceptions_state_mc_catch): New function.
	(throw_exception): Adjust.
	* common/common-exceptions.h (exceptions_state_mc_init): Remove
	all parameters.
	(exceptions_state_mc_catch): Declare.
	(TRY_CATCH): Rename to ...
	(TRY): ... this.  Remove EXCEPTION and MASK parameters.
	(CATCH, END_CATCH): New.
	All callers adjusted.

gdb/gdbserver/ChangeLog:
2015-03-07  Pedro Alves  <palves@redhat.com>

	Adjust all callers of TRY_CATCH to use TRY/CATCH/END_CATCH
	instead.
2015-03-07 15:14:14 +00:00

236 lines
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/* CLI Definitions for GDB, the GNU debugger.
Copyright (C) 2002-2015 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 "defs.h"
#include "interps.h"
#include "event-top.h"
#include "ui-out.h"
#include "cli-out.h"
#include "top.h" /* for "execute_command" */
#include "infrun.h"
#include "observer.h"
/* These are the ui_out and the interpreter for the console
interpreter. */
struct ui_out *cli_uiout;
static struct interp *cli_interp;
/* Longjmp-safe wrapper for "execute_command". */
static struct gdb_exception safe_execute_command (struct ui_out *uiout,
char *command,
int from_tty);
/* Observers for several run control events. If the interpreter is
quiet (i.e., another interpreter is being run with
interpreter-exec), print nothing. */
/* Observer for the signal_received notification. */
static void
cli_on_signal_received (enum gdb_signal siggnal)
{
if (!interp_quiet_p (cli_interp))
print_signal_received_reason (cli_uiout, siggnal);
}
/* Observer for the end_stepping_range notification. */
static void
cli_on_end_stepping_range (void)
{
if (!interp_quiet_p (cli_interp))
print_end_stepping_range_reason (cli_uiout);
}
/* Observer for the signalled notification. */
static void
cli_on_signal_exited (enum gdb_signal siggnal)
{
if (!interp_quiet_p (cli_interp))
print_signal_exited_reason (cli_uiout, siggnal);
}
/* Observer for the exited notification. */
static void
cli_on_exited (int exitstatus)
{
if (!interp_quiet_p (cli_interp))
print_exited_reason (cli_uiout, exitstatus);
}
/* Observer for the no_history notification. */
static void
cli_on_no_history (void)
{
if (!interp_quiet_p (cli_interp))
print_no_history_reason (cli_uiout);
}
/* Observer for the sync_execution_done notification. */
static void
cli_on_sync_execution_done (void)
{
if (!interp_quiet_p (cli_interp))
display_gdb_prompt (NULL);
}
/* Observer for the command_error notification. */
static void
cli_on_command_error (void)
{
if (!interp_quiet_p (cli_interp))
display_gdb_prompt (NULL);
}
/* These implement the cli out interpreter: */
static void *
cli_interpreter_init (struct interp *self, int top_level)
{
/* If changing this, remember to update tui-interp.c as well. */
observer_attach_end_stepping_range (cli_on_end_stepping_range);
observer_attach_signal_received (cli_on_signal_received);
observer_attach_signal_exited (cli_on_signal_exited);
observer_attach_exited (cli_on_exited);
observer_attach_no_history (cli_on_no_history);
observer_attach_sync_execution_done (cli_on_sync_execution_done);
observer_attach_command_error (cli_on_command_error);
return NULL;
}
static int
cli_interpreter_resume (void *data)
{
struct ui_file *stream;
/*sync_execution = 1; */
/* gdb_setup_readline will change gdb_stdout. If the CLI was
previously writing to gdb_stdout, then set it to the new
gdb_stdout afterwards. */
stream = cli_out_set_stream (cli_uiout, gdb_stdout);
if (stream != gdb_stdout)
{
cli_out_set_stream (cli_uiout, stream);
stream = NULL;
}
gdb_setup_readline ();
if (stream != NULL)
cli_out_set_stream (cli_uiout, gdb_stdout);
return 1;
}
static int
cli_interpreter_suspend (void *data)
{
gdb_disable_readline ();
return 1;
}
static struct gdb_exception
cli_interpreter_exec (void *data, const char *command_str)
{
struct ui_file *old_stream;
struct gdb_exception result;
/* FIXME: cagney/2003-02-01: Need to const char *propogate
safe_execute_command. */
char *str = strcpy (alloca (strlen (command_str) + 1), command_str);
/* gdb_stdout could change between the time cli_uiout was
initialized and now. Since we're probably using a different
interpreter which has a new ui_file for gdb_stdout, use that one
instead of the default.
It is important that it gets reset everytime, since the user
could set gdb to use a different interpreter. */
old_stream = cli_out_set_stream (cli_uiout, gdb_stdout);
result = safe_execute_command (cli_uiout, str, 1);
cli_out_set_stream (cli_uiout, old_stream);
return result;
}
static struct gdb_exception
safe_execute_command (struct ui_out *command_uiout, char *command, int from_tty)
{
struct gdb_exception e = exception_none;
struct ui_out *saved_uiout;
/* Save and override the global ``struct ui_out'' builder. */
saved_uiout = current_uiout;
current_uiout = command_uiout;
TRY
{
execute_command (command, from_tty);
}
CATCH (exception, RETURN_MASK_ALL)
{
e = exception;
}
END_CATCH
/* Restore the global builder. */
current_uiout = saved_uiout;
/* FIXME: cagney/2005-01-13: This shouldn't be needed. Instead the
caller should print the exception. */
exception_print (gdb_stderr, e);
return e;
}
static struct ui_out *
cli_ui_out (struct interp *self)
{
return cli_uiout;
}
/* Standard gdb initialization hook. */
extern initialize_file_ftype _initialize_cli_interp; /* -Wmissing-prototypes */
void
_initialize_cli_interp (void)
{
static const struct interp_procs procs = {
cli_interpreter_init, /* init_proc */
cli_interpreter_resume, /* resume_proc */
cli_interpreter_suspend, /* suspend_proc */
cli_interpreter_exec, /* exec_proc */
cli_ui_out, /* ui_out_proc */
NULL, /* set_logging_proc */
cli_command_loop /* command_loop_proc */
};
/* Create a default uiout builder for the CLI. */
cli_uiout = cli_out_new (gdb_stdout);
cli_interp = interp_new (INTERP_CONSOLE, &procs);
interp_add (cli_interp);
}
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