except.c

来自「GCC编译器源代码」· C语言 代码 · 共 1,417 行 · 第 1/3 页

/* Handle exceptional things in C++.
   Copyright (C) 1989, 92-96, 1997 Free Software Foundation, Inc.
   Contributed by Michael Tiemann <[e-mail]>
   Rewritten by Mike Stump <[e-mail]>, based upon an
   initial re-implementation courtesy Tad Hunt.

This file is part of GNU CC.

GNU CC 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 2, or (at your option)
any later version.

GNU CC 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 GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */


#include "config.h"
#include <stdio.h>
#include "tree.h"
#include "rtl.h"
#include "cp-tree.h"
#include "flags.h"
#include "obstack.h"
#include "expr.h"
#include "output.h"
#include "except.h"
#include "function.h"
#include "defaults.h"

rtx expand_builtin_return_addr	PROTO((enum built_in_function, int, rtx));

/* Holds the fndecl for __builtin_return_address.  */
tree builtin_return_address_fndecl;

/* A couple of backend routines from m88k.c */

/* Used to cache a call to __builtin_return_address.  */
static tree BuiltinReturnAddress;
     
static void easy_expand_asm PROTO((char *));
static void push_eh_cleanup PROTO((void));
static void do_unwind PROTO((rtx));
static rtx do_function_call PROTO((tree, tree, tree));
static tree build_eh_type_type PROTO((tree));
static tree build_eh_type PROTO((tree));
static void expand_end_eh_spec PROTO((tree));

static void
easy_expand_asm (str)
     char *str;
{
  expand_asm (build_string (strlen (str)+1, str));
}


#if 0
/* This is the startup, and finish stuff per exception table.  */

/* XXX - Tad: exception handling section */
#ifndef EXCEPT_SECTION_ASM_OP
#define EXCEPT_SECTION_ASM_OP	"section\t.gcc_except_table,\"a\",@progbits"
#endif

#ifdef EXCEPT_SECTION_ASM_OP
typedef struct {
    void *start_region;
    void *end_region;
    void *exception_handler;
 } exception_table;
#endif /* EXCEPT_SECTION_ASM_OP */

#ifdef EXCEPT_SECTION_ASM_OP

 /* on machines which support it, the exception table lives in another section,
	but it needs a label so we can reference it...  This sets up that
    label! */
asm (EXCEPT_SECTION_ASM_OP);
exception_table __EXCEPTION_TABLE__[1] = { (void*)0, (void*)0, (void*)0 };
asm (TEXT_SECTION_ASM_OP);

#endif /* EXCEPT_SECTION_ASM_OP */

#ifdef EXCEPT_SECTION_ASM_OP

 /* we need to know where the end of the exception table is... so this
    is how we do it! */

asm (EXCEPT_SECTION_ASM_OP);
exception_table __EXCEPTION_END__[1] = { (void*)-1, (void*)-1, (void*)-1 };
asm (TEXT_SECTION_ASM_OP);

#endif /* EXCEPT_SECTION_ASM_OP */

#endif

#include "decl.h"
#include "insn-flags.h"
#include "obstack.h"

/* ======================================================================
   Briefly the algorithm works like this:

     When a constructor or start of a try block is encountered,
     push_eh_entry (&eh_stack) is called.  Push_eh_entry () creates a
     new entry in the unwind protection stack and returns a label to
     output to start the protection for that block.

     When a destructor or end try block is encountered, pop_eh_entry
     (&eh_stack) is called.  Pop_eh_entry () returns the eh_entry it
     created when push_eh_entry () was called.  The eh_entry structure
     contains three things at this point.  The start protect label,
     the end protect label, and the exception handler label.  The end
     protect label should be output before the call to the destructor
     (if any). If it was a destructor, then its parse tree is stored
     in the finalization variable in the eh_entry structure.  Otherwise
     the finalization variable is set to NULL to reflect the fact that
     is the the end of a try block.  Next, this modified eh_entry node
     is enqueued in the finalizations queue by calling
     enqueue_eh_entry (&queue,entry).

	+---------------------------------------------------------------+
	|XXX: Will need modification to deal with partially		|
	|			constructed arrays of objects		|
	|								|
	|	Basically, this consists of keeping track of how many	|
	|	of the objects have been constructed already (this	|
	|	should be in a register though, so that shouldn't be a	|
	|	problem.						|
	+---------------------------------------------------------------+

     When a catch block is encountered, there is a lot of work to be
     done.

     Since we don't want to generate the catch block inline with the
     regular flow of the function, we need to have some way of doing
     so.  Luckily, we can use sequences to defer the catch sections.
     When the start of a catch block is encountered, we start the
     sequence.  After the catch block is generated, we end the
     sequence.

     Next we must insure that when the catch block is executed, all
     finalizations for the matching try block have been completed.  If
     any of those finalizations throw an exception, we must call
     terminate according to the ARM (section r.15.6.1).  What this
     means is that we need to dequeue and emit finalizations for each
     entry in the eh_queue until we get to an entry with a NULL
     finalization field.  For any of the finalization entries, if it
     is not a call to terminate (), we must protect it by giving it
     another start label, end label, and exception handler label,
     setting its finalization tree to be a call to terminate (), and
     enqueue'ing this new eh_entry to be output at an outer level.
     Finally, after all that is done, we can get around to outputting
     the catch block which basically wraps all the "catch (...) {...}"
     statements in a big if/then/else construct that matches the
     correct block to call.
     
     ===================================================================== */

/* local globals for function calls
   ====================================================================== */

/* Used to cache "terminate", "unexpected", "set_terminate", and
   "set_unexpected" after default_conversion. (lib-except.c)  */
static tree Terminate, Unexpected, SetTerminate, SetUnexpected, CatchMatch;

/* Used to cache __find_first_exception_table_match for throw.  */
static tree FirstExceptionMatch;

/* Used to cache a call to __unwind_function.  */
static tree Unwind;

/* Holds a ready to emit call to "terminate".  */
static tree TerminateFunctionCall;

/* ====================================================================== */


/* ========================================================================= */



/* local globals - these local globals are for storing data necessary for
   generating the exception table and code in the correct order.

   ========================================================================= */

/* Holds the pc for doing "throw" */
static tree saved_pc;

extern int throw_used;
extern rtx catch_clauses;

/* ========================================================================= */

/* Cheesyness to save some typing.  Returns the return value rtx.  */

static rtx
do_function_call (func, params, return_type)
     tree func, params, return_type;
{
  tree func_call;
  func_call = build_function_call (func, params);
  expand_call (func_call, NULL_RTX, 0);
  if (return_type != NULL_TREE)
    return hard_function_value (return_type, func_call);
  return NULL_RTX;
}

/* ========================================================================= */

/* sets up all the global eh stuff that needs to be initialized at the
   start of compilation.

   This includes:
		- Setting up all the function call trees.  */

void
init_exception_processing ()
{
  tree unexpected_fndecl, terminate_fndecl;
  tree set_unexpected_fndecl, set_terminate_fndecl;
  tree catch_match_fndecl;
  tree find_first_exception_match_fndecl;
  tree unwind_fndecl;
  tree declspecs;
  tree d;

  /* void vtype () */
  tree vtype = build_function_type (void_type_node, void_list_node);
  
  /* void (*)() */
  tree PFV = build_pointer_type (vtype);

  /* Arg list for the build_function_type call for set_terminate and
     set_unexpected.  */
  tree pfvlist = tree_cons (NULL_TREE, PFV, void_list_node);

  /* void (*pfvtype (void (*) ()))() */
  tree pfvtype = build_function_type (PFV, pfvlist);

  set_terminate_fndecl = auto_function (get_identifier ("set_terminate"),
					pfvtype, NOT_BUILT_IN);
  set_unexpected_fndecl = auto_function (get_identifier ("set_unexpected"),
					 pfvtype, NOT_BUILT_IN);
  unexpected_fndecl = auto_function (get_identifier ("unexpected"),
				     vtype, NOT_BUILT_IN);
  terminate_fndecl = auto_function (get_identifier ("terminate"),
				    vtype, NOT_BUILT_IN);
  TREE_THIS_VOLATILE (terminate_fndecl) = 1;

  push_lang_context (lang_name_c);

  catch_match_fndecl
    = builtin_function (flag_rtti
			? "__throw_type_match_rtti"
			: "__throw_type_match",
			build_function_type (ptr_type_node,
					     tree_cons (NULL_TREE, ptr_type_node,
							tree_cons (NULL_TREE, ptr_type_node,
								   tree_cons (NULL_TREE, ptr_type_node,
									      void_list_node)))),
			NOT_BUILT_IN, NULL_PTR);
  find_first_exception_match_fndecl
    = builtin_function ("__find_first_exception_table_match",
			build_function_type (ptr_type_node,
					     tree_cons (NULL_TREE, ptr_type_node,
							void_list_node)),
			NOT_BUILT_IN, NULL_PTR);
  unwind_fndecl
    = builtin_function ("__unwind_function",
			build_function_type (void_type_node,
					     tree_cons (NULL_TREE, ptr_type_node,
							void_list_node)),
			NOT_BUILT_IN, NULL_PTR);

  Unexpected = default_conversion (unexpected_fndecl);
  Terminate = default_conversion (terminate_fndecl);
  SetTerminate = default_conversion (set_terminate_fndecl);
  SetUnexpected = default_conversion (set_unexpected_fndecl);
  CatchMatch = default_conversion (catch_match_fndecl);
  FirstExceptionMatch = default_conversion (find_first_exception_match_fndecl);
  Unwind = default_conversion (unwind_fndecl);
  BuiltinReturnAddress = default_conversion (builtin_return_address_fndecl);

  TerminateFunctionCall = build_function_call (Terminate, NULL_TREE);

  pop_lang_context ();

  d = build_decl (VAR_DECL, get_identifier ("__eh_pc"), ptr_type_node);
  TREE_PUBLIC (d) = 1;
  DECL_EXTERNAL (d) = 1;
  DECL_ARTIFICIAL (d) = 1;
  cp_finish_decl (d, NULL_TREE, NULL_TREE, 0, 0);
  saved_pc = d;

  /* If we use setjmp/longjmp EH, arrange for all cleanup actions to
     be protected with __terminate.  */
  protect_cleanup_actions_with_terminate = 1;
}

/* Retrieve a pointer to the cp_eh_info node for the current exception.  */

static tree
call_eh_info ()
{
  tree fn;

  fn = get_identifier ("__cp_exception_info");
  if (IDENTIFIER_GLOBAL_VALUE (fn))
    fn = IDENTIFIER_GLOBAL_VALUE (fn);
  else
    {
      tree t, fields[6];

      /* Declare cp_eh_info * __cp_exception_info (void),
	 as defined in exception.cc. */
      push_obstacks_nochange ();
      end_temporary_allocation ();

      /* struct cp_eh_info.  This must match exception.cc.  Note that this
	 type is not pushed anywhere.  */
      t = make_lang_type (RECORD_TYPE);
      fields[0] = build_lang_field_decl (FIELD_DECL, get_identifier ("value"),
					 ptr_type_node);
      fields[1] = build_lang_field_decl (FIELD_DECL, get_identifier ("type"),
					 ptr_type_node);
      fields[2] = build_lang_field_decl
	(FIELD_DECL, get_identifier ("cleanup"),
	 build_pointer_type (build_function_type
			     (ptr_type_node, tree_cons
			      (NULL_TREE, ptr_type_node, void_list_node))));
      fields[3] = build_lang_field_decl (FIELD_DECL, get_identifier ("caught"),
					 boolean_type_node);
      fields[4] = build_lang_field_decl (FIELD_DECL, get_identifier ("next"),
					 build_pointer_type (t));
      fields[5] = build_lang_field_decl
	(FIELD_DECL, get_identifier ("handlers"), long_integer_type_node);
      /* N.B.: The fourth field LEN is expected to be
	 the number of fields - 1, not the total number of fields.  */
      finish_builtin_type (t, "cp_eh_info", fields, 5, ptr_type_node);
      t = build_pointer_type (t);

      /* And now the function.  */
      fn = build_lang_decl (FUNCTION_DECL, fn,
			    build_function_type (t, void_list_node));
      DECL_EXTERNAL (fn) = 1;
      TREE_PUBLIC (fn) = 1;
      DECL_ARTIFICIAL (fn) = 1;
      pushdecl_top_level (fn);
      make_function_rtl (fn);
      assemble_external (fn);
      pop_obstacks ();
    }
  return build_function_call (fn, NULL_TREE);
}

/* Retrieve a pointer to the cp_eh_info node for the current exception
   and save it in the current binding level.  */

static void
push_eh_info ()
{
  tree decl, fn = call_eh_info ();

  /* Remember the pointer to the current exception info; it won't change
     during this catch block.  */
  decl = build_decl (VAR_DECL, get_identifier ("__exception_info"),
		     TREE_TYPE (fn));
  DECL_ARTIFICIAL (decl) = 1;
  DECL_INITIAL (decl) = fn;
  decl = pushdecl (decl);
  cp_finish_decl (decl, fn, NULL_TREE, 0, 0);
}

/* Returns a reference to the cp_eh_info node for the current exception.  */

static tree
get_eh_info ()
{
  /* Look for the pointer pushed in push_eh_info.  */
  tree t = lookup_name (get_identifier ("__exception_info"), 0);
  return build_indirect_ref (t, NULL_PTR);
}

/* Returns a reference to the current exception object.  */

static tree
get_eh_value ()
{
  return build_component_ref (get_eh_info (), get_identifier ("value"),
			      NULL_TREE, 0);
}

/* Returns a reference to the current exception type.  */

static tree
get_eh_type ()
{
  return build_component_ref (get_eh_info (), get_identifier ("type"),
			      NULL_TREE, 0);
}

/* Returns a reference to whether or not the current exception
   has been caught.  */

static tree
get_eh_caught ()
{
  return build_component_ref (get_eh_info (), get_identifier ("caught"),
			      NULL_TREE, 0);
}

/* Returns a reference to whether or not the current exception
   has been caught.  */

static tree
get_eh_handlers ()
{
  return build_component_ref (get_eh_info (), get_identifier ("handlers"),
			      NULL_TREE, 0);
}

/* Build a type value for use at runtime for a type that is matched
   against by the exception handling system.  */

static tree
build_eh_type_type (type)
     tree type;
{
  char *typestring;
  tree exp;

  if (type == error_mark_node)
    return error_mark_node;

  /* peel back references, so they match.  */
  if (TREE_CODE (type) == REFERENCE_TYPE)
    type = TREE_TYPE (type);

  /* Peel off cv qualifiers.  */
  type = TYPE_MAIN_VARIANT (type);

  if (flag_rtti)
    {
      return build1 (ADDR_EXPR, ptr_type_node, get_typeid (type));
    }

  typestring = build_overload_name (type, 1, 1);
  exp = combine_strings (build_string (strlen (typestring)+1, typestring));
  return build1 (ADDR_EXPR, ptr_type_node, exp);
}

/* Build a type value for use at runtime for a exp that is thrown or
   matched against by the exception handling system.  */

static tree
build_eh_type (exp)
     tree exp;
{
  if (flag_rtti)
    {
      exp = build_typeid (exp);
      return build1 (ADDR_EXPR, ptr_type_node, exp);
    }
  return build_eh_type_type (TREE_TYPE (exp));