binutils-gdb/gdb/python/py-finishbreakpoint.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

484 lines
14 KiB
C

/* Python interface to finish breakpoints
Copyright (C) 2011-2015 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 "python-internal.h"
#include "breakpoint.h"
#include "frame.h"
#include "gdbthread.h"
#include "arch-utils.h"
#include "language.h"
#include "observer.h"
#include "inferior.h"
#include "block.h"
/* Function that is called when a Python finish bp is found out of scope. */
static char * const outofscope_func = "out_of_scope";
/* struct implementing the gdb.FinishBreakpoint object by extending
the gdb.Breakpoint class. */
struct finish_breakpoint_object
{
/* gdb.Breakpoint base class. */
gdbpy_breakpoint_object py_bp;
/* gdb.Type object of the value return by the breakpointed function.
May be NULL if no debug information was available or return type
was VOID. */
PyObject *return_type;
/* gdb.Value object of the function finished by this breakpoint. Will be
NULL if return_type is NULL. */
PyObject *function_value;
/* When stopped at this FinishBreakpoint, gdb.Value object returned by
the function; Py_None if the value is not computable; NULL if GDB is
not stopped at a FinishBreakpoint. */
PyObject *return_value;
};
extern PyTypeObject finish_breakpoint_object_type
CPYCHECKER_TYPE_OBJECT_FOR_TYPEDEF ("finish_breakpoint_object");
/* Python function to get the 'return_value' attribute of
FinishBreakpoint. */
static PyObject *
bpfinishpy_get_returnvalue (PyObject *self, void *closure)
{
struct finish_breakpoint_object *self_finishbp =
(struct finish_breakpoint_object *) self;
if (!self_finishbp->return_value)
Py_RETURN_NONE;
Py_INCREF (self_finishbp->return_value);
return self_finishbp->return_value;
}
/* Deallocate FinishBreakpoint object. */
static void
bpfinishpy_dealloc (PyObject *self)
{
struct finish_breakpoint_object *self_bpfinish =
(struct finish_breakpoint_object *) self;
Py_XDECREF (self_bpfinish->function_value);
Py_XDECREF (self_bpfinish->return_type);
Py_XDECREF (self_bpfinish->return_value);
}
/* Triggered when gdbpy_should_stop is about to execute the `stop' callback
of the gdb.FinishBreakpoint object BP_OBJ. Will compute and cache the
`return_value', if possible. */
void
bpfinishpy_pre_stop_hook (struct gdbpy_breakpoint_object *bp_obj)
{
struct finish_breakpoint_object *self_finishbp =
(struct finish_breakpoint_object *) bp_obj;
/* Can compute return_value only once. */
gdb_assert (!self_finishbp->return_value);
if (!self_finishbp->return_type)
return;
TRY
{
struct value *function =
value_object_to_value (self_finishbp->function_value);
struct type *value_type =
type_object_to_type (self_finishbp->return_type);
struct value *ret = get_return_value (function, value_type);
if (ret)
{
self_finishbp->return_value = value_to_value_object (ret);
if (!self_finishbp->return_value)
gdbpy_print_stack ();
}
else
{
Py_INCREF (Py_None);
self_finishbp->return_value = Py_None;
}
}
CATCH (except, RETURN_MASK_ALL)
{
gdbpy_convert_exception (except);
gdbpy_print_stack ();
}
END_CATCH
}
/* Triggered when gdbpy_should_stop has triggered the `stop' callback
of the gdb.FinishBreakpoint object BP_OBJ. */
void
bpfinishpy_post_stop_hook (struct gdbpy_breakpoint_object *bp_obj)
{
TRY
{
/* Can't delete it here, but it will be removed at the next stop. */
disable_breakpoint (bp_obj->bp);
gdb_assert (bp_obj->bp->disposition == disp_del);
}
CATCH (except, RETURN_MASK_ALL)
{
gdbpy_convert_exception (except);
gdbpy_print_stack ();
}
END_CATCH
}
/* Python function to create a new breakpoint. */
static int
bpfinishpy_init (PyObject *self, PyObject *args, PyObject *kwargs)
{
static char *keywords[] = { "frame", "internal", NULL };
struct finish_breakpoint_object *self_bpfinish =
(struct finish_breakpoint_object *) self;
int type = bp_breakpoint;
PyObject *frame_obj = NULL;
int thread;
struct frame_info *frame = NULL; /* init for gcc -Wall */
struct frame_info *prev_frame = NULL;
struct frame_id frame_id;
PyObject *internal = NULL;
int internal_bp = 0;
CORE_ADDR finish_pc, pc;
char *addr_str, small_buf[100];
struct symbol *function;
if (!PyArg_ParseTupleAndKeywords (args, kwargs, "|OO", keywords,
&frame_obj, &internal))
return -1;
TRY
{
/* Default frame to newest frame if necessary. */
if (frame_obj == NULL)
frame = get_current_frame ();
else
frame = frame_object_to_frame_info (frame_obj);
if (frame == NULL)
{
PyErr_SetString (PyExc_ValueError,
_("Invalid ID for the `frame' object."));
}
else
{
prev_frame = get_prev_frame (frame);
if (prev_frame == 0)
{
PyErr_SetString (PyExc_ValueError,
_("\"FinishBreakpoint\" not "
"meaningful in the outermost "
"frame."));
}
else if (get_frame_type (prev_frame) == DUMMY_FRAME)
{
PyErr_SetString (PyExc_ValueError,
_("\"FinishBreakpoint\" cannot "
"be set on a dummy frame."));
}
else
{
frame_id = get_frame_id (prev_frame);
if (frame_id_eq (frame_id, null_frame_id))
PyErr_SetString (PyExc_ValueError,
_("Invalid ID for the `frame' object."));
}
}
}
CATCH (except, RETURN_MASK_ALL)
{
gdbpy_convert_exception (except);
return -1;
}
END_CATCH
if (PyErr_Occurred ())
return -1;
thread = pid_to_thread_id (inferior_ptid);
if (thread == 0)
{
PyErr_SetString (PyExc_ValueError,
_("No thread currently selected."));
return -1;
}
if (internal)
{
internal_bp = PyObject_IsTrue (internal);
if (internal_bp == -1)
{
PyErr_SetString (PyExc_ValueError,
_("The value of `internal' must be a boolean."));
return -1;
}
}
/* Find the function we will return from. */
self_bpfinish->return_type = NULL;
self_bpfinish->function_value = NULL;
TRY
{
if (get_frame_pc_if_available (frame, &pc))
{
function = find_pc_function (pc);
if (function != NULL)
{
struct type *ret_type =
TYPE_TARGET_TYPE (SYMBOL_TYPE (function));
/* Remember only non-void return types. */
if (TYPE_CODE (ret_type) != TYPE_CODE_VOID)
{
struct value *func_value;
/* Ignore Python errors at this stage. */
self_bpfinish->return_type = type_to_type_object (ret_type);
PyErr_Clear ();
func_value = read_var_value (function, frame);
self_bpfinish->function_value =
value_to_value_object (func_value);
PyErr_Clear ();
}
}
}
}
CATCH (except, RETURN_MASK_ALL)
{
/* Just swallow. Either the return type or the function value
remain NULL. */
}
END_CATCH
if (self_bpfinish->return_type == NULL || self_bpfinish->function_value == NULL)
{
/* Won't be able to compute return value. */
Py_XDECREF (self_bpfinish->return_type);
Py_XDECREF (self_bpfinish->function_value);
self_bpfinish->return_type = NULL;
self_bpfinish->function_value = NULL;
}
bppy_pending_object = &self_bpfinish->py_bp;
bppy_pending_object->number = -1;
bppy_pending_object->bp = NULL;
TRY
{
/* Set a breakpoint on the return address. */
finish_pc = get_frame_pc (prev_frame);
xsnprintf (small_buf, sizeof (small_buf), "*%s", hex_string (finish_pc));
addr_str = small_buf;
create_breakpoint (python_gdbarch,
addr_str, NULL, thread, NULL,
0,
1 /*temp_flag*/,
bp_breakpoint,
0,
AUTO_BOOLEAN_TRUE,
&bkpt_breakpoint_ops,
0, 1, internal_bp, 0);
}
CATCH (except, RETURN_MASK_ALL)
{
GDB_PY_SET_HANDLE_EXCEPTION (except);
}
END_CATCH
self_bpfinish->py_bp.bp->frame_id = frame_id;
self_bpfinish->py_bp.is_finish_bp = 1;
/* Bind the breakpoint with the current program space. */
self_bpfinish->py_bp.bp->pspace = current_program_space;
return 0;
}
/* Called when GDB notices that the finish breakpoint BP_OBJ is out of
the current callstack. Triggers the method OUT_OF_SCOPE if implemented,
then delete the breakpoint. */
static void
bpfinishpy_out_of_scope (struct finish_breakpoint_object *bpfinish_obj)
{
gdbpy_breakpoint_object *bp_obj = (gdbpy_breakpoint_object *) bpfinish_obj;
PyObject *py_obj = (PyObject *) bp_obj;
if (bpfinish_obj->py_bp.bp->enable_state == bp_enabled
&& PyObject_HasAttrString (py_obj, outofscope_func))
{
PyObject *meth_result;
meth_result = PyObject_CallMethod (py_obj, outofscope_func, NULL);
if (meth_result == NULL)
gdbpy_print_stack ();
Py_XDECREF (meth_result);
}
delete_breakpoint (bpfinish_obj->py_bp.bp);
}
/* Callback for `bpfinishpy_detect_out_scope'. Triggers Python's
`B->out_of_scope' function if B is a FinishBreakpoint out of its scope. */
static int
bpfinishpy_detect_out_scope_cb (struct breakpoint *b, void *args)
{
struct breakpoint *bp_stopped = (struct breakpoint *) args;
PyObject *py_bp = (PyObject *) b->py_bp_object;
struct gdbarch *garch = b->gdbarch ? b->gdbarch : get_current_arch ();
/* Trigger out_of_scope if this is a FinishBreakpoint and its frame is
not anymore in the current callstack. */
if (py_bp != NULL && b->py_bp_object->is_finish_bp)
{
struct finish_breakpoint_object *finish_bp =
(struct finish_breakpoint_object *) py_bp;
/* Check scope if not currently stopped at the FinishBreakpoint. */
if (b != bp_stopped)
{
TRY
{
if (b->pspace == current_inferior ()->pspace
&& (!target_has_registers
|| frame_find_by_id (b->frame_id) == NULL))
bpfinishpy_out_of_scope (finish_bp);
}
CATCH (except, RETURN_MASK_ALL)
{
gdbpy_convert_exception (except);
gdbpy_print_stack ();
}
END_CATCH
}
}
return 0;
}
/* Attached to `stop' notifications, check if the execution has run
out of the scope of any FinishBreakpoint before it has been hit. */
static void
bpfinishpy_handle_stop (struct bpstats *bs, int print_frame)
{
struct cleanup *cleanup = ensure_python_env (get_current_arch (),
current_language);
iterate_over_breakpoints (bpfinishpy_detect_out_scope_cb,
bs == NULL ? NULL : bs->breakpoint_at);
do_cleanups (cleanup);
}
/* Attached to `exit' notifications, triggers all the necessary out of
scope notifications. */
static void
bpfinishpy_handle_exit (struct inferior *inf)
{
struct cleanup *cleanup = ensure_python_env (target_gdbarch (),
current_language);
iterate_over_breakpoints (bpfinishpy_detect_out_scope_cb, NULL);
do_cleanups (cleanup);
}
/* Initialize the Python finish breakpoint code. */
int
gdbpy_initialize_finishbreakpoints (void)
{
if (PyType_Ready (&finish_breakpoint_object_type) < 0)
return -1;
if (gdb_pymodule_addobject (gdb_module, "FinishBreakpoint",
(PyObject *) &finish_breakpoint_object_type) < 0)
return -1;
observer_attach_normal_stop (bpfinishpy_handle_stop);
observer_attach_inferior_exit (bpfinishpy_handle_exit);
return 0;
}
static PyGetSetDef finish_breakpoint_object_getset[] = {
{ "return_value", bpfinishpy_get_returnvalue, NULL,
"gdb.Value object representing the return value, if any. \
None otherwise.", NULL },
{ NULL } /* Sentinel. */
};
PyTypeObject finish_breakpoint_object_type =
{
PyVarObject_HEAD_INIT (NULL, 0)
"gdb.FinishBreakpoint", /*tp_name*/
sizeof (struct finish_breakpoint_object), /*tp_basicsize*/
0, /*tp_itemsize*/
bpfinishpy_dealloc, /*tp_dealloc*/
0, /*tp_print*/
0, /*tp_getattr*/
0, /*tp_setattr*/
0, /*tp_compare*/
0, /*tp_repr*/
0, /*tp_as_number*/
0, /*tp_as_sequence*/
0, /*tp_as_mapping*/
0, /*tp_hash */
0, /*tp_call*/
0, /*tp_str*/
0, /*tp_getattro*/
0, /*tp_setattro */
0, /*tp_as_buffer*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /*tp_flags*/
"GDB finish breakpoint object", /* tp_doc */
0, /* tp_traverse */
0, /* tp_clear */
0, /* tp_richcompare */
0, /* tp_weaklistoffset */
0, /* tp_iter */
0, /* tp_iternext */
0, /* tp_methods */
0, /* tp_members */
finish_breakpoint_object_getset,/* tp_getset */
&breakpoint_object_type, /* tp_base */
0, /* tp_dict */
0, /* tp_descr_get */
0, /* tp_descr_set */
0, /* tp_dictoffset */
bpfinishpy_init, /* tp_init */
0, /* tp_alloc */
0 /* tp_new */
};