path: root/gcc/m2/gm2-gcc/m2except.cc

/* m2except.cc implements the construction of exception trees.

Copyright (C) 2012-2025 Free Software Foundation, Inc.
Contributed by Gaius Mulley <gaius@glam.ac.uk>.

This file is part of GNU Modula-2.

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

GNU Modula-2 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 Modula-2; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "gcc-consolidation.h"

#include "../m2-tree.h"

#define GM2
#define GM2_BUG_REPORT                                                        \
  "Please report this crash to the GNU Modula-2 mailing list "                \
  "<gm2@nongnu.org>\n"

/* External functions.  */

#define m2except_c
#include "m2assert.h"
#include "m2block.h"
#include "m2decl.h"
#include "m2expr.h"
#include "m2statement.h"
#include "m2tree.h"
#include "m2treelib.h"
#include "m2type.h"

/* Local prototypes.  */

#include "m2except.h"

static tree build_exc_ptr (location_t location);
static tree do_begin_catch (location_t location);
static tree do_end_catch (location_t location);
static tree begin_handler (location_t location);
static void finish_handler (location_t location, tree handler);
static tree finish_handler_parms (location_t location, tree handler);
static void finish_handler_sequence (tree try_block);
static tree begin_try_block (location_t location);
static tree finish_expr_stmt (location_t location, tree expr);
static tree maybe_cleanup_point_expr_void (tree expr);
static tree build_target_expr_with_type (location_t location, tree init,
                                         tree type);
static tree get_target_expr (location_t location, tree init);
static tree build_eh_type_type (location_t location, tree type);
static tree get_tinfo_decl_m2 (location_t location);
static tree eh_type_info (location_t location, tree type);
static tree build_address (tree t);

void _M2_gm2except_init (void);
void _M2_gm2except_finally (void);

/* Exception handling library functions.  */

static GTY (()) tree fn_begin_catch_tree = NULL_TREE;
static GTY (()) tree fn_end_catch_tree = NULL_TREE;
static GTY (()) tree fn_throw_tree = NULL_TREE;
static GTY (()) tree fn_rethrow_tree = NULL_TREE;
static GTY (()) tree cleanup_type = NULL_TREE;
static GTY (()) tree fn_allocate_exception_tree = NULL_TREE;
static GTY (()) tree fn_free_exception_tree = NULL_TREE;
static GTY (()) tree gm2_eh_int_type = NULL_TREE;

/* Modula-2 linker fodder.  */

void
_M2_gm2except_init (void)
{
}
void
_M2_gm2except_finally (void)
{
}

/* InitExceptions - initialize this module, it declares the external
   functions and assigns them to the appropriate global tree
   variables.  */

void
m2except_InitExceptions (location_t location)
{
  tree t;

  m2assert_AssertLocation (location);
  m2block_pushGlobalScope ();
  flag_exceptions = 1;
  init_eh ();

  m2decl_BuildStartFunctionDeclaration (FALSE);
  fn_rethrow_tree = m2decl_BuildEndFunctionDeclaration (
     location, location, "__cxa_rethrow", void_type_node, TRUE, FALSE,
     TRUE, FALSE);
  TREE_NOTHROW (fn_rethrow_tree) = 0;

  m2decl_BuildStartFunctionDeclaration (FALSE);
  m2decl_BuildParameterDeclaration (location, NULL, ptr_type_node, FALSE);
  fn_begin_catch_tree = m2decl_BuildEndFunctionDeclaration (
      location, location, "__cxa_begin_catch", ptr_type_node, TRUE, FALSE,
      TRUE, FALSE);
  m2decl_BuildStartFunctionDeclaration (FALSE);
  fn_end_catch_tree = m2decl_BuildEndFunctionDeclaration (
      location, location, "__cxa_end_catch", void_type_node, TRUE, FALSE,
      TRUE, FALSE);
  /* This can throw if the destructor for the exception throws.  */
  TREE_NOTHROW (fn_end_catch_tree) = 0;

  /* The CLEANUP_TYPE is the internal type of a destructor.  */
  t = void_list_node;
  t = tree_cons (NULL_TREE, ptr_type_node, t);
  t = build_function_type (void_type_node, t);
  cleanup_type = build_pointer_type (t);

  /* Declare void __cxa_throw (void*, void*, void (*)(void*)).  */
  m2decl_BuildStartFunctionDeclaration (FALSE);
  m2decl_BuildParameterDeclaration (location, NULL, cleanup_type, FALSE);
  m2decl_BuildParameterDeclaration (location, NULL, ptr_type_node, FALSE);
  m2decl_BuildParameterDeclaration (location, NULL, ptr_type_node, FALSE);
  fn_throw_tree = m2decl_BuildEndFunctionDeclaration (
      location, location, "__cxa_throw", void_type_node, TRUE, FALSE, TRUE,
      TRUE);

  /* Declare void __cxa_rethrow (void).  */
  m2decl_BuildStartFunctionDeclaration (FALSE);
  fn_rethrow_tree = m2decl_BuildEndFunctionDeclaration (
     location, location, "__cxa_rethrow", void_type_node, TRUE, FALSE, TRUE,
     TRUE);

  /* Declare void *__cxa_allocate_exception (size_t).  */
  m2decl_BuildStartFunctionDeclaration (FALSE);
  m2decl_BuildParameterDeclaration (location, NULL, size_type_node, FALSE);
  fn_allocate_exception_tree = m2decl_BuildEndFunctionDeclaration (
      location, location, "__cxa_allocate_exception", ptr_type_node, TRUE,
      FALSE, TRUE, FALSE);

  /* Declare void *__cxa_free_exception (void *).  */
  m2decl_BuildStartFunctionDeclaration (FALSE);
  m2decl_BuildParameterDeclaration (location, NULL, ptr_type_node, FALSE);
  fn_free_exception_tree = m2decl_BuildEndFunctionDeclaration (
      location, location, "__cxa_free_exception", ptr_type_node, TRUE, FALSE,
      TRUE, FALSE);

  /* Define integer type exception type which will match C++ int type
     in the C++ runtime library.  */
  gm2_eh_int_type = build_eh_type_type (location, integer_type_node);
  m2block_popGlobalScope ();

  MARK_TS_TYPED (TRY_BLOCK);
  MARK_TS_TYPED (THROW_EXPR);
  MARK_TS_TYPED (HANDLER);
  MARK_TS_TYPED (EXPR_STMT);
}

/* do_call0 - return a tree containing: call builtin_function ().  */

static tree
do_call0 (location_t location, tree builtin_function)
{
  tree function = build_address (builtin_function);
  tree fntype = TREE_TYPE (TREE_TYPE (function));
  tree result_type = TREE_TYPE (fntype);

  m2assert_AssertLocation (location);
  return build_call_array_loc (location, result_type, function, 0, NULL);
}

/* do_call1 - return a tree containing: call builtin_function
   (param1).  */

static tree
do_call1 (location_t location, tree builtin_function, tree param1)
{
  tree *argarray = XALLOCAVEC (tree, 1);
  tree function = build_address (builtin_function);
  tree fntype = TREE_TYPE (TREE_TYPE (function));
  tree result_type = TREE_TYPE (fntype);

  m2assert_AssertLocation (location);
  argarray[0] = param1;
  return build_call_array_loc (location, result_type, function, 1, argarray);
}

/* do_call3 - return a tree containing: call builtin_function
   (param1, param2, param3).  */

static tree
do_call3 (location_t location, tree builtin_function, tree param1, tree param2,
          tree param3)
{
  tree *argarray = XALLOCAVEC (tree, 3);
  tree function = build_address (builtin_function);
  tree fntype = TREE_TYPE (TREE_TYPE (function));
  tree result_type = TREE_TYPE (fntype);

  m2assert_AssertLocation (location);
  argarray[0] = param1;
  argarray[1] = param2;
  argarray[2] = param3;
  return build_call_array_loc (location, result_type, function, 3, argarray);
}

/* build_exc_ptr - creates the GCC internal type, pointer to
   exception control block.  */

static tree
build_exc_ptr (location_t location)
{
  m2assert_AssertLocation (location);
  return do_call1 (location, builtin_decl_explicit (BUILT_IN_EH_POINTER),
                   integer_zero_node);
}

static tree
get_tinfo_decl_m2 (location_t location)
{
  tree t = build_decl (location, VAR_DECL, get_identifier ("_ZTIi"),
                       ptr_type_node);

  m2assert_AssertLocation (location);
  TREE_STATIC (t) = 1;
  DECL_EXTERNAL (t) = 1;
  TREE_PUBLIC (t) = 1;
  DECL_ARTIFICIAL (t) = 1;
  DECL_IGNORED_P (t) = 1;
  m2block_pushDecl (t);
  make_decl_rtl (t);
  return t;
}

/* Return the type info for TYPE as used by EH machinery.  */

static tree
eh_type_info (location_t location, tree type)
{
  m2assert_AssertLocation (location);
  if (type == NULL_TREE || type == error_mark_node)
    return type;

  return get_tinfo_decl_m2 (location);
}

/* Return an ADDR_EXPR giving the address of T.  This function
   attempts no optimizations or simplifications; it is a low-level
   primitive.  */

static tree
build_address (tree t)
{
  tree addr = build1 (ADDR_EXPR, build_pointer_type (TREE_TYPE (t)), t);

  return addr;
}

/* Build the address of a typeinfo decl for use in the runtime
   matching field of the exception model.  */

static tree
build_eh_type_type (location_t location, tree type)
{
  tree exp = eh_type_info (location, type);

  m2assert_AssertLocation (location);
  if (!exp)
    return NULL;

  TREE_USED (exp) = 1;

  return convert (ptr_type_node, build_address (exp));
}

/* Build a TARGET_EXPR, initializing the DECL with the VALUE.  */

static tree
build_target_expr (tree decl, tree value)
{
  tree t = build4 (TARGET_EXPR, TREE_TYPE (decl), decl, value, NULL_TREE,
                   NULL_TREE);

  /* We always set TREE_SIDE_EFFECTS so that expand_expr does not
     ignore the TARGET_EXPR.  If there really turn out to be no
     side-effects, then the optimizer should be able to get rid of
     whatever code is generated anyhow.  */
  TREE_SIDE_EFFECTS (t) = 1;

  return t;
}

/* Return an undeclared local temporary of type TYPE for use in
   building a TARGET_EXPR.  */

static tree
build_local_temp (location_t location, tree type)
{
  tree slot = build_decl (location, VAR_DECL, NULL_TREE, type);

  m2assert_AssertLocation (location);
  DECL_ARTIFICIAL (slot) = 1;
  DECL_IGNORED_P (slot) = 1;
  DECL_CONTEXT (slot) = current_function_decl;
  layout_decl (slot, 0);
  return slot;
}

/* Build a TARGET_EXPR using INIT to initialize a new temporary of
   the indicated TYPE.  */

static tree
build_target_expr_with_type (location_t location, tree init, tree type)
{
  tree slot;

  m2assert_AssertLocation (location);
  gcc_assert (!VOID_TYPE_P (type));

  if (TREE_CODE (init) == TARGET_EXPR)
    return init;

  slot = build_local_temp (location, type);
  return build_target_expr (slot, init);
}

/* Like build_target_expr_with_type, but use the type of INIT.  */

static tree
get_target_expr (location_t location, tree init)
{
  m2assert_AssertLocation (location);
  return build_target_expr_with_type (location, init, TREE_TYPE (init));
}

/* do_allocate_exception - returns a tree which calls
   allocate_exception (sizeof (type)); */

static tree
do_allocate_exception (location_t location, tree type)
{
  return do_call1 (location, fn_allocate_exception_tree, size_in_bytes (type));
}

/* Call __cxa_free_exception from a cleanup.  This is never invoked
   directly, but see the comment for stabilize_throw_expr.  */

static tree
do_free_exception (location_t location, tree ptr)
{
  return do_call1 (location, fn_free_exception_tree, ptr);
}

/* do_throw - returns tree for a call to throw (ptr, gm2_eh_int_type,
   0).  */

static tree
do_throw (location_t location, tree ptr)
{
  return do_call3 (location, fn_throw_tree, ptr,
                   unshare_expr (gm2_eh_int_type),
                   build_int_cst (cleanup_type, 0));
}

/* do_rethrow - returns a tree containing the call to rethrow ().  */

static tree
do_rethrow (location_t location)
{
  return do_call0 (location, fn_rethrow_tree);
}

/* gm2_build_throw - build a GCC throw expression tree which looks
   identical to the C++ front end.  */

static tree
gm2_build_throw (location_t location, tree exp)
{
  m2assert_AssertLocation (location);

  if (exp == NULL_TREE)
    /* Rethrow the current exception.  */
    exp = build1 (THROW_EXPR, void_type_node, do_rethrow (location));
  else
    {
      tree object, ptr;
      tree allocate_expr;
      tree tmp;

      exp = m2expr_FoldAndStrip (
          convert (m2type_GetIntegerType (), m2expr_FoldAndStrip (exp)));
      exp = m2expr_GetIntegerOne (location);

      /* Allocate the space for the exception.  */
      allocate_expr = do_allocate_exception (location, TREE_TYPE (exp));
      allocate_expr = get_target_expr (location, allocate_expr);
      ptr = TARGET_EXPR_SLOT (allocate_expr);
      TARGET_EXPR_CLEANUP (allocate_expr) = do_free_exception (location, ptr);
      CLEANUP_EH_ONLY (allocate_expr) = 1;

      object = build1 (NOP_EXPR, build_pointer_type (TREE_TYPE (exp)), ptr);
      object = m2expr_BuildIndirect (location, object, TREE_TYPE (exp));

      /* And initialize the exception object.  */
      exp = build2 (INIT_EXPR, TREE_TYPE (object), object, exp);

      /* Prepend the allocation.  */
      exp = build2 (COMPOUND_EXPR, TREE_TYPE (exp), allocate_expr, exp);

      /* Force all the cleanups to be evaluated here so that we don't have
	 to do them during unwinding.  */
      exp = build1 (CLEANUP_POINT_EXPR, void_type_node, exp);

      tmp = do_throw (location, ptr);

      /* Tack on the initialization stuff.  */
      exp = build2 (COMPOUND_EXPR, TREE_TYPE (tmp), exp, tmp);
      exp = build1 (THROW_EXPR, void_type_node, exp);
    }

  SET_EXPR_LOCATION (exp, location);
  return exp;
}

/* gccgm2_BuildThrow - builds a throw expression and return the tree.  */

tree
m2except_BuildThrow (location_t location, tree expr)
{
  return gm2_build_throw (location, expr);
}

/* Build up a call to __cxa_begin_catch, to tell the runtime that the
   exception has been handled.  */

static tree
do_begin_catch (location_t location)
{
  return do_call1 (location, fn_begin_catch_tree, build_exc_ptr (location));
}

/* Build up a call to __cxa_end_catch, to destroy the exception
   object for the current catch block if no others are currently using
   it.  */

static tree
do_end_catch (location_t location)
{
  tree cleanup = do_call0 (location, fn_end_catch_tree);

  m2assert_AssertLocation (location);
  TREE_NOTHROW (cleanup) = 1;
  return cleanup;
}

/* BuildTryBegin - returns a tree representing the 'try' block.  */

tree
m2except_BuildTryBegin (location_t location)
{
  m2assert_AssertLocation (location);
  return begin_try_block (location);
}

/* BuildTryEnd - builds the end of the Try block and prepares for the
   catch handlers.  */

void
m2except_BuildTryEnd (tree try_block)
{
  TRY_STMTS (try_block) = m2block_pop_statement_list ();
  TRY_HANDLERS (try_block) = m2block_begin_statement_list ();

  /* Now ensure that all successive add_stmts adds to this statement
     sequence.  */
  m2block_push_statement_list (TRY_HANDLERS (try_block));
}

/* BuildCatchBegin - creates a handler tree for the C++ statement
   'catch (...) {'.  It returns the handler tree.  */

tree
m2except_BuildCatchBegin (location_t location)
{
  tree handler = begin_handler (location);

  m2assert_AssertLocation (location);
  return finish_handler_parms (location, handler);
}

/* BuildCatchEnd - completes a try catch block.  It returns the,
   try_block, tree.  It creates the C++ statement
   '}' which matches the catch above.  */

tree
m2except_BuildCatchEnd (location_t location, tree handler, tree try_block)
{
  m2assert_AssertLocation (location);
  finish_handler (location, handler);
  finish_handler_sequence (try_block);
  return try_block;
}

/* Begin a handler.  Returns a HANDLER if appropriate.  */

static tree
begin_handler (location_t location)
{
  tree r;

  m2assert_AssertLocation (location);
  r = build_stmt (location, HANDLER, NULL_TREE, NULL_TREE);
  add_stmt (location, r);

  HANDLER_BODY (r) = m2block_begin_statement_list ();

  /* Now ensure that all successive add_stmts adds to this
     statement sequence.  */
  m2block_push_statement_list (HANDLER_BODY (r));
  return r;
}

/* Finish a handler, which may be given by HANDLER.  The BLOCKs are
   the return value from the matching call to finish_handler_parms.  */

static void
finish_handler (location_t location, tree handler)
{
  /* We might need to rethrow the exception if we reach the end.
     use this code:  finish_expr_stmt (build_throw (NULL_TREE));  */
  tree body = m2block_pop_statement_list ();

  m2assert_AssertLocation (location);
  HANDLER_BODY (handler) = body;
  HANDLER_BODY (handler) = build2 (TRY_FINALLY_EXPR, void_type_node, body,
                                   do_end_catch (location));
}

/* Finish the handler-parameters for a handler, which may be given by
   HANDLER.  */

static tree
finish_handler_parms (location_t location, tree handler)
{
  m2assert_AssertLocation (location);
  /* Equivalent to C++ catch (...).  */
  finish_expr_stmt (location, do_begin_catch (location));

  HANDLER_TYPE (handler) = NULL_TREE;
  return handler;
}

/* Finish a handler-sequence for a try-block, which may be given by
   TRY_BLOCK.  */

static void
finish_handler_sequence (tree try_block)
{
  TRY_HANDLERS (try_block) = m2block_pop_statement_list ();
}

/* Begin a try-block.  Returns a newly-created TRY_BLOCK if
   appropriate.  */

static tree
begin_try_block (location_t location)
{
  tree r = build_stmt (location, TRY_BLOCK, NULL_TREE, NULL_TREE);

  m2assert_AssertLocation (location);
  TRY_STMTS (r) = m2block_begin_statement_list ();

  /* Now ensure that all successive add_stmts adds to this statement
     sequence.  */
  m2block_push_statement_list (TRY_STMTS (r));
  return r;
}

/* Finish an expression-statement, whose EXPRESSION is as indicated.  */

static tree
finish_expr_stmt (location_t location, tree expr)
{
  tree r = NULL_TREE;

  m2assert_AssertLocation (location);
  if (expr != NULL_TREE)
    {
      expr = build1 (CONVERT_EXPR, void_type_node, expr);

      /* Simplification of inner statement expressions, compound exprs, etc
         can result in us already having an EXPR_STMT.  */
      if (TREE_CODE (expr) != CLEANUP_POINT_EXPR)
        {
          if (TREE_CODE (expr) != EXPR_STMT)
            expr = build_stmt (location, EXPR_STMT, expr);
          expr = maybe_cleanup_point_expr_void (expr);
        }
      r = add_stmt (location, expr);
    }

  return r;
}

/* Like maybe_cleanup_point_expr except have the type of the new
   expression be void so we don't need to create a temporary variable to
   hold the inner expression.  The reason why we do this is because the
   original type might be an aggregate and we cannot create a temporary
   variable for that type.  */

static tree
maybe_cleanup_point_expr_void (tree expr)
{
  return fold_build_cleanup_point_expr (void_type_node, expr);
}

#include "gt-m2-m2except.h"