binutils-gdb/gdb/interps.h
Pedro Alves b885aea1bb Simplify interp::exec / interp_exec - let exceptions propagate
This patch implements a simplication that I suggested here:

  https://sourceware.org/pipermail/gdb-patches/2022-March/186320.html

Currently, the interp::exec virtual method interface is such that
subclass implementations must catch exceptions and then return them
via normal function return.

However, higher up the in chain, for the CLI we get to
interpreter_exec_cmd, which does:

  for (i = 1; i < nrules; i++)
    {
      struct gdb_exception e = interp_exec (interp_to_use, prules[i]);

      if (e.reason < 0)
	{
	  interp_set (old_interp, 0);
	  error (_("error in command: \"%s\"."), prules[i]);
	}
    }

and for MI we get to mi_cmd_interpreter_exec, which has:

  void
  mi_cmd_interpreter_exec (const char *command, char **argv, int argc)
  {
  ...
    for (i = 1; i < argc; i++)
      {
	struct gdb_exception e = interp_exec (interp_to_use, argv[i]);

	if (e.reason < 0)
	  error ("%s", e.what ());
      }
  }

Note that if those errors are reached, we lose the original
exception's error code.  I can't see why we'd want that.

And, I can't see why we need to have interp_exec catch the exception
and return it via the normal return path.  That's normally needed when
we need to handle propagating exceptions across C code, like across
readline or ncurses, but that's not the case here.

It seems to me that we can simplify things by removing some
try/catch-ing and just letting exceptions propagate normally.

Note, the "error in command" error shown above, which only exists in
the CLI interpreter-exec command, is only ever printed AFAICS if you
run "interpreter-exec console" when the top level interpreter is
already the console/tui.  Like:

 (gdb) interpreter-exec console "foobar"
 Undefined command: "foobar".  Try "help".
 error in command: "foobar".

You won't see it with MI's "-interpreter-exec console" from a top
level MI interpreter:

 (gdb)
 -interpreter-exec console "foobar"
 &"Undefined command: \"foobar\".  Try \"help\".\n"
 ^error,msg="Undefined command: \"foobar\".  Try \"help\"."
 (gdb)

nor with MI's "-interpreter-exec mi" from a top level MI interpreter:

 (gdb)
 -interpreter-exec mi "-foobar"
 ^error,msg="Undefined MI command: foobar",code="undefined-command"
 ^done
 (gdb)

in both these cases because MI's -interpreter-exec just does:

  error ("%s", e.what ());

You won't see it either when running an MI command with the CLI's
"interpreter-exec mi":

 (gdb) interpreter-exec mi "-foobar"
 ^error,msg="Undefined MI command: foobar",code="undefined-command"
 (gdb)

This last case is because MI's interp::exec implementation never
returns an error:

 gdb_exception
 mi_interp::exec (const char *command)
 {
   mi_execute_command_wrapper (command);
   return gdb_exception ();
 }

Thus I think that "error in command" error is pretty pointless, and
since it simplifies things to not have it, the patch just removes it.

The patch also ends up addressing an old FIXME.

Change-Id: I5a6432a80496934ac7127594c53bf5221622e393
Approved-By: Tom Tromey <tromey@adacore.com>
Approved-By: Kevin Buettner <kevinb@redhat.com>
2023-02-08 17:28:42 +00:00

185 lines
5.8 KiB
C++

/* Manages interpreters for GDB, the GNU debugger.
Copyright (C) 2000-2023 Free Software Foundation, Inc.
Written by Jim Ingham <jingham@apple.com> of Apple Computer, 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/>. */
#ifndef INTERPS_H
#define INTERPS_H
struct ui_out;
struct interp;
struct ui;
class completion_tracker;
typedef struct interp *(*interp_factory_func) (const char *name);
/* Each interpreter kind (CLI, MI, etc.) registers itself with a call
to this function, passing along its name, and a pointer to a
function that creates a new instance of an interpreter with that
name. */
extern void interp_factory_register (const char *name,
interp_factory_func func);
extern void interp_exec (struct interp *interp, const char *command);
class interp
{
public:
explicit interp (const char *name);
virtual ~interp () = 0;
virtual void init (bool top_level)
{}
virtual void resume () = 0;
virtual void suspend () = 0;
virtual void exec (const char *command) = 0;
/* Returns the ui_out currently used to collect results for this
interpreter. It can be a formatter for stdout, as is the case
for the console & mi outputs, or it might be a result
formatter. */
virtual ui_out *interp_ui_out () = 0;
/* Provides a hook for interpreters to do any additional
setup/cleanup that they might need when logging is enabled or
disabled. */
virtual void set_logging (ui_file_up logfile, bool logging_redirect,
bool debug_redirect) = 0;
/* Called before starting an event loop, to give the interpreter a
chance to e.g., print a prompt. */
virtual void pre_command_loop ()
{}
/* Returns true if this interpreter supports using the readline
library; false if it uses GDB's own simplified readline
emulation. */
virtual bool supports_command_editing ()
{ return false; }
const char *name () const
{
return m_name.get ();
}
private:
/* This is the name in "-i=" and "set interpreter". */
gdb::unique_xmalloc_ptr<char> m_name;
public:
/* Interpreters are stored in a linked list, this is the next
one... */
struct interp *next;
/* Has the init method been run? */
bool inited = false;
};
/* Look up the interpreter for NAME, creating one if none exists yet.
If NAME is not a interpreter type previously registered with
interp_factory_register, return NULL; otherwise return a pointer to
the interpreter. */
extern struct interp *interp_lookup (struct ui *ui, const char *name);
/* Set the current UI's top level interpreter to the interpreter named
NAME. Throws an error if NAME is not a known interpreter or the
interpreter fails to initialize. */
extern void set_top_level_interpreter (const char *name);
/* Temporarily set the current interpreter, and reset it on
destruction. */
class scoped_restore_interp
{
public:
scoped_restore_interp (const char *name)
: m_interp (set_interp (name))
{
}
~scoped_restore_interp ()
{
set_interp (m_interp->name ());
}
scoped_restore_interp (const scoped_restore_interp &) = delete;
scoped_restore_interp &operator= (const scoped_restore_interp &) = delete;
private:
struct interp *set_interp (const char *name);
struct interp *m_interp;
};
extern int current_interp_named_p (const char *name);
/* Call this function to give the current interpreter an opportunity
to do any special handling of streams when logging is enabled or
disabled. LOGFILE is the stream for the log file when logging is
starting and is NULL when logging is ending. LOGGING_REDIRECT is
the value of the "set logging redirect" setting. If true, the
interpreter should configure the output streams to send output only
to the logfile. If false, the interpreter should configure the
output streams to send output to both the current output stream
(i.e., the terminal) and the log file. DEBUG_REDIRECT is same as
LOGGING_REDIRECT, but for the value of "set logging debugredirect"
instead. */
extern void current_interp_set_logging (ui_file_up logfile,
bool logging_redirect,
bool debug_redirect);
/* Returns the top-level interpreter. */
extern struct interp *top_level_interpreter (void);
/* Return the current UI's current interpreter. */
extern struct interp *current_interpreter (void);
extern struct interp *command_interp (void);
extern void clear_interpreter_hooks (void);
/* Returns true if INTERP supports using the readline library; false
if it uses GDB's own simplified form of readline. */
extern int interp_supports_command_editing (struct interp *interp);
/* Called before starting an event loop, to give the interpreter a
chance to e.g., print a prompt. */
extern void interp_pre_command_loop (struct interp *interp);
/* List the possible interpreters which could complete the given
text. */
extern void interpreter_completer (struct cmd_list_element *ignore,
completion_tracker &tracker,
const char *text,
const char *word);
/* well-known interpreters */
#define INTERP_CONSOLE "console"
#define INTERP_MI2 "mi2"
#define INTERP_MI3 "mi3"
#define INTERP_MI4 "mi4"
#define INTERP_MI "mi"
#define INTERP_TUI "tui"
#define INTERP_INSIGHT "insight"
#endif