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binutils-gdb/gdb/frame-unwind.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

290 lines
8.7 KiB
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/* Definitions for frame unwinder, for GDB, the GNU debugger.
Copyright (C) 2003-2015 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 "frame.h"
#include "frame-unwind.h"
#include "dummy-frame.h"
#include "inline-frame.h"
#include "value.h"
#include "regcache.h"
#include "gdb_obstack.h"
#include "target.h"
static struct gdbarch_data *frame_unwind_data;
struct frame_unwind_table_entry
{
const struct frame_unwind *unwinder;
struct frame_unwind_table_entry *next;
};
struct frame_unwind_table
{
struct frame_unwind_table_entry *list;
/* The head of the OSABI part of the search list. */
struct frame_unwind_table_entry **osabi_head;
};
static void *
frame_unwind_init (struct obstack *obstack)
{
struct frame_unwind_table *table
= OBSTACK_ZALLOC (obstack, struct frame_unwind_table);
/* Start the table out with a few default sniffers. OSABI code
can't override this. */
table->list = OBSTACK_ZALLOC (obstack, struct frame_unwind_table_entry);
table->list->unwinder = &dummy_frame_unwind;
table->list->next = OBSTACK_ZALLOC (obstack,
struct frame_unwind_table_entry);
table->list->next->unwinder = &inline_frame_unwind;
/* The insertion point for OSABI sniffers. */
table->osabi_head = &table->list->next->next;
return table;
}
void
frame_unwind_prepend_unwinder (struct gdbarch *gdbarch,
const struct frame_unwind *unwinder)
{
struct frame_unwind_table *table = gdbarch_data (gdbarch, frame_unwind_data);
struct frame_unwind_table_entry *entry;
/* Insert the new entry at the start of the list. */
entry = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry);
entry->unwinder = unwinder;
entry->next = (*table->osabi_head);
(*table->osabi_head) = entry;
}
void
frame_unwind_append_unwinder (struct gdbarch *gdbarch,
const struct frame_unwind *unwinder)
{
struct frame_unwind_table *table = gdbarch_data (gdbarch, frame_unwind_data);
struct frame_unwind_table_entry **ip;
/* Find the end of the list and insert the new entry there. */
for (ip = table->osabi_head; (*ip) != NULL; ip = &(*ip)->next);
(*ip) = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry);
(*ip)->unwinder = unwinder;
}
/* Call SNIFFER from UNWINDER. If it succeeded set UNWINDER for
THIS_FRAME and return 1. Otherwise the function keeps THIS_FRAME
unchanged and returns 0. */
static int
frame_unwind_try_unwinder (struct frame_info *this_frame, void **this_cache,
const struct frame_unwind *unwinder)
{
struct cleanup *old_cleanup;
int res = 0;
old_cleanup = frame_prepare_for_sniffer (this_frame, unwinder);
TRY
{
res = unwinder->sniffer (unwinder, this_frame, this_cache);
}
CATCH (ex, RETURN_MASK_ERROR)
{
if (ex.error == NOT_AVAILABLE_ERROR)
{
/* This usually means that not even the PC is available,
thus most unwinders aren't able to determine if they're
the best fit. Keep trying. Fallback prologue unwinders
should always accept the frame. */
do_cleanups (old_cleanup);
return 0;
}
throw_exception (ex);
}
END_CATCH
if (res)
{
discard_cleanups (old_cleanup);
return 1;
}
else
{
do_cleanups (old_cleanup);
return 0;
}
gdb_assert_not_reached ("frame_unwind_try_unwinder");
}
/* Iterate through sniffers for THIS_FRAME frame until one returns with an
unwinder implementation. THIS_FRAME->UNWIND must be NULL, it will get set
by this function. Possibly initialize THIS_CACHE. */
void
frame_unwind_find_by_frame (struct frame_info *this_frame, void **this_cache)
{
struct gdbarch *gdbarch = get_frame_arch (this_frame);
struct frame_unwind_table *table = gdbarch_data (gdbarch, frame_unwind_data);
struct frame_unwind_table_entry *entry;
const struct frame_unwind *unwinder_from_target;
unwinder_from_target = target_get_unwinder ();
if (unwinder_from_target != NULL
&& frame_unwind_try_unwinder (this_frame, this_cache,
unwinder_from_target))
return;
unwinder_from_target = target_get_tailcall_unwinder ();
if (unwinder_from_target != NULL
&& frame_unwind_try_unwinder (this_frame, this_cache,
unwinder_from_target))
return;
for (entry = table->list; entry != NULL; entry = entry->next)
if (frame_unwind_try_unwinder (this_frame, this_cache, entry->unwinder))
return;
internal_error (__FILE__, __LINE__, _("frame_unwind_find_by_frame failed"));
}
/* A default frame sniffer which always accepts the frame. Used by
fallback prologue unwinders. */
int
default_frame_sniffer (const struct frame_unwind *self,
struct frame_info *this_frame,
void **this_prologue_cache)
{
return 1;
}
/* The default frame unwinder stop_reason callback. */
enum unwind_stop_reason
default_frame_unwind_stop_reason (struct frame_info *this_frame,
void **this_cache)
{
struct frame_id this_id = get_frame_id (this_frame);
if (frame_id_eq (this_id, outer_frame_id))
return UNWIND_OUTERMOST;
else
return UNWIND_NO_REASON;
}
/* Helper functions for value-based register unwinding. These return
a (possibly lazy) value of the appropriate type. */
/* Return a value which indicates that FRAME did not save REGNUM. */
struct value *
frame_unwind_got_optimized (struct frame_info *frame, int regnum)
{
struct gdbarch *gdbarch = frame_unwind_arch (frame);
struct type *type = register_type (gdbarch, regnum);
struct value *val;
/* Return an lval_register value, so that we print it as
"<not saved>". */
val = allocate_value_lazy (type);
set_value_lazy (val, 0);
mark_value_bytes_optimized_out (val, 0, TYPE_LENGTH (type));
VALUE_LVAL (val) = lval_register;
VALUE_REGNUM (val) = regnum;
VALUE_FRAME_ID (val) = get_frame_id (frame);
return val;
}
/* Return a value which indicates that FRAME copied REGNUM into
register NEW_REGNUM. */
struct value *
frame_unwind_got_register (struct frame_info *frame,
int regnum, int new_regnum)
{
return value_of_register_lazy (frame, new_regnum);
}
/* Return a value which indicates that FRAME saved REGNUM in memory at
ADDR. */
struct value *
frame_unwind_got_memory (struct frame_info *frame, int regnum, CORE_ADDR addr)
{
struct gdbarch *gdbarch = frame_unwind_arch (frame);
struct value *v = value_at_lazy (register_type (gdbarch, regnum), addr);
set_value_stack (v, 1);
return v;
}
/* Return a value which indicates that FRAME's saved version of
REGNUM has a known constant (computed) value of VAL. */
struct value *
frame_unwind_got_constant (struct frame_info *frame, int regnum,
ULONGEST val)
{
struct gdbarch *gdbarch = frame_unwind_arch (frame);
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
struct value *reg_val;
reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
store_unsigned_integer (value_contents_writeable (reg_val),
register_size (gdbarch, regnum), byte_order, val);
return reg_val;
}
struct value *
frame_unwind_got_bytes (struct frame_info *frame, int regnum, gdb_byte *buf)
{
struct gdbarch *gdbarch = frame_unwind_arch (frame);
struct value *reg_val;
reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
memcpy (value_contents_raw (reg_val), buf, register_size (gdbarch, regnum));
return reg_val;
}
/* Return a value which indicates that FRAME's saved version of REGNUM
has a known constant (computed) value of ADDR. Convert the
CORE_ADDR to a target address if necessary. */
struct value *
frame_unwind_got_address (struct frame_info *frame, int regnum,
CORE_ADDR addr)
{
struct gdbarch *gdbarch = frame_unwind_arch (frame);
struct value *reg_val;
reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
pack_long (value_contents_writeable (reg_val),
register_type (gdbarch, regnum), addr);
return reg_val;
}
/* -Wmissing-prototypes */
extern initialize_file_ftype _initialize_frame_unwind;
void
_initialize_frame_unwind (void)
{
frame_unwind_data = gdbarch_data_register_pre_init (frame_unwind_init);
}
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