Google Git
Sign in
gnu / gcc / 9b1856d6c8c54a1b4b7e3a312f46a76f6d89c3df / . / gcc / cp / cvt.c
blob: 6029e8427169120259505a99a2745225c7510a5a [file] [log] [blame]
/* Language-level data type conversion for GNU C++.
Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
1999, 2000 Free Software Foundation, Inc.
Hacked by Michael Tiemann (tiemann@cygnus.com)
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. */
/* This file contains the functions for converting C expressions
to different data types. The only entry point is `convert'.
Every language front end must have a `convert' function
but what kind of conversions it does will depend on the language. */
#include "config.h"
#include "system.h"
#include "tree.h"
#include "flags.h"
#include "cp-tree.h"
#include "convert.h"
#include "toplev.h"
#include "decl.h"
static tree cp_convert_to_pointer PARAMS ((tree, tree, int));
static tree convert_to_pointer_force PARAMS ((tree, tree));
static tree build_up_reference PARAMS ((tree, tree, int, tree));
static void warn_ref_binding PARAMS ((tree, tree, tree));
/* Change of width--truncation and extension of integers or reals--
is represented with NOP_EXPR. Proper functioning of many things
assumes that no other conversions can be NOP_EXPRs.
Conversion between integer and pointer is represented with CONVERT_EXPR.
Converting integer to real uses FLOAT_EXPR
and real to integer uses FIX_TRUNC_EXPR.
Here is a list of all the functions that assume that widening and
narrowing is always done with a NOP_EXPR:
In convert.c, convert_to_integer.
In c-typeck.c, build_binary_op_nodefault (boolean ops),
and truthvalue_conversion.
In expr.c: expand_expr, for operands of a MULT_EXPR.
In fold-const.c: fold.
In tree.c: get_narrower and get_unwidened.
C++: in multiple-inheritance, converting between pointers may involve
adjusting them by a delta stored within the class definition. */
/* Subroutines of `convert'. */
/* if converting pointer to pointer
if dealing with classes, check for derived->base or vice versa
else if dealing with method pointers, delegate
else convert blindly
else if converting class, pass off to build_type_conversion
else try C-style pointer conversion. If FORCE is true then allow
conversions via virtual bases (these are permitted by reinterpret_cast,
but not static_cast). */
static tree
cp_convert_to_pointer (type, expr, force)
tree type, expr;
int force;
{
register tree intype = TREE_TYPE (expr);
register enum tree_code form;
tree rval;
if (IS_AGGR_TYPE (intype))
{
intype = complete_type (intype);
if (!COMPLETE_TYPE_P (intype))
{
error ("can't convert from incomplete type `%T' to `%T'",
intype, type);
return error_mark_node;
}
rval = build_type_conversion (type, expr, 1);
if (rval)
{
if (rval == error_mark_node)
error ("conversion of `%E' from `%T' to `%T' is ambiguous",
expr, intype, type);
return rval;
}
}
/* Handle anachronistic conversions from (::*)() to cv void* or (*)(). */
if (TREE_CODE (type) == POINTER_TYPE
&& (TREE_CODE (TREE_TYPE (type)) == FUNCTION_TYPE
|| VOID_TYPE_P (TREE_TYPE (type))))
{
/* Allow an implicit this pointer for pointer to member
functions. */
if (TYPE_PTRMEMFUNC_P (intype))
{
tree fntype = TREE_TYPE (TYPE_PTRMEMFUNC_FN_TYPE (intype));
tree decl = maybe_dummy_object (TYPE_METHOD_BASETYPE (fntype), 0);
expr = build (OFFSET_REF, fntype, decl, expr);
}
if (TREE_CODE (expr) == OFFSET_REF
&& TREE_CODE (TREE_TYPE (expr)) == METHOD_TYPE)
expr = resolve_offset_ref (expr);
if (TREE_CODE (TREE_TYPE (expr)) == METHOD_TYPE)
expr = build_addr_func (expr);
if (TREE_CODE (TREE_TYPE (expr)) == POINTER_TYPE)
{
if (TREE_CODE (TREE_TYPE (TREE_TYPE (expr))) == METHOD_TYPE)
if (pedantic || warn_pmf2ptr)
pedwarn ("converting from `%T' to `%T'", TREE_TYPE (expr),
type);
return build1 (NOP_EXPR, type, expr);
}
intype = TREE_TYPE (expr);
}
form = TREE_CODE (intype);
if (POINTER_TYPE_P (intype))
{
intype = TYPE_MAIN_VARIANT (intype);
if (TYPE_MAIN_VARIANT (type) != intype
&& TREE_CODE (type) == POINTER_TYPE
&& TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
&& IS_AGGR_TYPE (TREE_TYPE (type))
&& IS_AGGR_TYPE (TREE_TYPE (intype))
&& TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
{
enum tree_code code = PLUS_EXPR;
tree binfo;
/* Try derived to base conversion. */
binfo = lookup_base (TREE_TYPE (intype), TREE_TYPE (type),
ba_check, NULL);
if (!binfo)
{
/* Try base to derived conversion. */
binfo = lookup_base (TREE_TYPE (type), TREE_TYPE (intype),
ba_check, NULL);
code = MINUS_EXPR;
}
if (binfo == error_mark_node)
return error_mark_node;
if (binfo)
{
expr = build_base_path (code, expr, binfo, 0);
/* Add any qualifier conversions. */
if (!same_type_p (TREE_TYPE (TREE_TYPE (expr)),
TREE_TYPE (type)))
{
expr = build1 (NOP_EXPR, type, expr);
TREE_CONSTANT (expr) =
TREE_CONSTANT (TREE_OPERAND (expr, 0));
}
return expr;
}
}
if (TYPE_PTRMEM_P (type) && TYPE_PTRMEM_P (intype))
{
tree b1;
tree b2;
tree binfo;
enum tree_code code = PLUS_EXPR;
base_kind bk;
b1 = TYPE_OFFSET_BASETYPE (TREE_TYPE (type));
b2 = TYPE_OFFSET_BASETYPE (TREE_TYPE (intype));
binfo = lookup_base (b1, b2, ba_check, &bk);
if (!binfo)
{
binfo = lookup_base (b2, b1, ba_check, &bk);
code = MINUS_EXPR;
}
if (binfo == error_mark_node)
return error_mark_node;
if (bk == bk_via_virtual)
{
if (force)
warning ("pointer to member cast from `%T' to `%T' is via virtual base",
TREE_TYPE (intype), TREE_TYPE (type));
else
{
error ("pointer to member cast from `%T' to `%T' is via virtual base",
TREE_TYPE (intype), TREE_TYPE (type));
return error_mark_node;
}
/* This is a reinterpret cast, whose result is unspecified.
We choose to do nothing. */
return build1 (NOP_EXPR, type, expr);
}
if (TREE_CODE (expr) == PTRMEM_CST)
expr = cplus_expand_constant (expr);
if (binfo)
expr = size_binop (code, convert (sizetype, expr),
BINFO_OFFSET (binfo));
}
else if (TYPE_PTRMEMFUNC_P (type))
{
error ("cannot convert `%E' from type `%T' to type `%T'",
expr, intype, type);
return error_mark_node;
}
rval = build1 (NOP_EXPR, type, expr);
TREE_CONSTANT (rval) = TREE_CONSTANT (expr);
return rval;
}
else if (TYPE_PTRMEMFUNC_P (type) && TYPE_PTRMEMFUNC_P (intype))
return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0);
else if (TYPE_PTRMEMFUNC_P (intype))
{
error ("cannot convert `%E' from type `%T' to type `%T'",
expr, intype, type);
return error_mark_node;
}
my_friendly_assert (form != OFFSET_TYPE, 186);
if (integer_zerop (expr))
{
if (TYPE_PTRMEMFUNC_P (type))
return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0);
if (TYPE_PTRMEM_P (type))
/* A NULL pointer-to-member is represented by -1, not by
zero. */
expr = build_int_2 (-1, -1);
else
expr = build_int_2 (0, 0);
TREE_TYPE (expr) = type;
return expr;
}
if (INTEGRAL_CODE_P (form))
{
if (TYPE_PRECISION (intype) == POINTER_SIZE)
return build1 (CONVERT_EXPR, type, expr);
expr = cp_convert (type_for_size (POINTER_SIZE, 0), expr);
/* Modes may be different but sizes should be the same. */
if (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (expr)))
!= GET_MODE_SIZE (TYPE_MODE (type)))
/* There is supposed to be some integral type
that is the same width as a pointer. */
abort ();
return convert_to_pointer (type, expr);
}
if (type_unknown_p (expr))
return instantiate_type (type, expr, itf_complain);
error ("cannot convert `%E' from type `%T' to type `%T'",
expr, intype, type);
return error_mark_node;
}
/* Like convert, except permit conversions to take place which
are not normally allowed due to access restrictions
(such as conversion from sub-type to private super-type). */
static tree
convert_to_pointer_force (type, expr)
tree type, expr;
{
register tree intype = TREE_TYPE (expr);
register enum tree_code form = TREE_CODE (intype);
if (integer_zerop (expr))
{
expr = build_int_2 (0, 0);
TREE_TYPE (expr) = type;
return expr;
}
if (form == POINTER_TYPE)
{
intype = TYPE_MAIN_VARIANT (intype);
if (TYPE_MAIN_VARIANT (type) != intype
&& TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
&& IS_AGGR_TYPE (TREE_TYPE (type))
&& IS_AGGR_TYPE (TREE_TYPE (intype))
&& TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
{
enum tree_code code = PLUS_EXPR;
tree binfo;
binfo = lookup_base (TREE_TYPE (intype), TREE_TYPE (type),
ba_ignore, NULL);
if (!binfo)
{
binfo = lookup_base (TREE_TYPE (type), TREE_TYPE (intype),
ba_ignore, NULL);
code = MINUS_EXPR;
}
if (binfo == error_mark_node)
return error_mark_node;
if (binfo)
{
expr = build_base_path (code, expr, binfo, 0);
/* Add any qualifier conversions. */
if (!same_type_p (TREE_TYPE (TREE_TYPE (expr)),
TREE_TYPE (type)))
{
expr = build1 (NOP_EXPR, type, expr);
TREE_CONSTANT (expr) =
TREE_CONSTANT (TREE_OPERAND (expr, 0));
}
return expr;
}
}
}
return cp_convert_to_pointer (type, expr, 1);
}
/* We are passing something to a function which requires a reference.
The type we are interested in is in TYPE. The initial
value we have to begin with is in ARG.
FLAGS controls how we manage access checking.
DIRECT_BIND in FLAGS controls how any temporaries are generated.
If DIRECT_BIND is set, DECL is the reference we're binding to. */
static tree
build_up_reference (type, arg, flags, decl)
tree type, arg, decl;
int flags;
{
tree rval;
tree argtype = TREE_TYPE (arg);
tree target_type = TREE_TYPE (type);
tree stmt_expr = NULL_TREE;
my_friendly_assert (TREE_CODE (type) == REFERENCE_TYPE, 187);
if ((flags & DIRECT_BIND) && ! real_lvalue_p (arg))
{
/* Create a new temporary variable. We can't just use a TARGET_EXPR
here because it needs to live as long as DECL. */
tree targ = arg;
arg = build_decl (VAR_DECL, NULL_TREE, argtype);
DECL_ARTIFICIAL (arg) = 1;
TREE_USED (arg) = 1;
TREE_STATIC (arg) = TREE_STATIC (decl);
if (TREE_STATIC (decl))
{
/* Namespace-scope or local static; give it a mangled name. */
tree name = mangle_ref_init_variable (decl);
DECL_NAME (arg) = name;
SET_DECL_ASSEMBLER_NAME (arg, name);
arg = pushdecl_top_level (arg);
}
else
{
/* Automatic; make sure we handle the cleanup properly. */
maybe_push_cleanup_level (argtype);
arg = pushdecl (arg);
}
/* Process the initializer for the declaration. */
DECL_INITIAL (arg) = targ;
cp_finish_decl (arg, targ, NULL_TREE,
LOOKUP_ONLYCONVERTING|DIRECT_BIND);
}
else if (!(flags & DIRECT_BIND) && ! lvalue_p (arg))
return get_target_expr (arg);
/* If we had a way to wrap this up, and say, if we ever needed its
address, transform all occurrences of the register, into a memory
reference we could win better. */
rval = build_unary_op (ADDR_EXPR, arg, 1);
if (rval == error_mark_node)
return error_mark_node;
if ((flags & LOOKUP_PROTECT)
&& TYPE_MAIN_VARIANT (argtype) != TYPE_MAIN_VARIANT (target_type)
&& IS_AGGR_TYPE (argtype)
&& IS_AGGR_TYPE (target_type))
{
/* We go through lookup_base for the access control. */
tree binfo = lookup_base (argtype, target_type, ba_check, NULL);
if (binfo == error_mark_node)
return error_mark_node;
if (binfo == NULL_TREE)
return error_not_base_type (target_type, argtype);
rval = build_base_path (PLUS_EXPR, rval, binfo, 1);
}
else
rval
= convert_to_pointer_force (build_pointer_type (target_type), rval);
rval = build1 (NOP_EXPR, type, rval);
TREE_CONSTANT (rval) = TREE_CONSTANT (TREE_OPERAND (rval, 0));
/* If we created and initialized a new temporary variable, add the
representation of that initialization to the RVAL. */
if (stmt_expr)
rval = build (COMPOUND_EXPR, TREE_TYPE (rval), stmt_expr, rval);
/* And return the result. */
return rval;
}
/* Subroutine of convert_to_reference. REFTYPE is the target reference type.
INTYPE is the original rvalue type and DECL is an optional _DECL node
for diagnostics.
[dcl.init.ref] says that if an rvalue is used to
initialize a reference, then the reference must be to a
non-volatile const type. */
static void
warn_ref_binding (reftype, intype, decl)
tree reftype, intype, decl;
{
tree ttl = TREE_TYPE (reftype);
if (!CP_TYPE_CONST_NON_VOLATILE_P (ttl))
{
const char *msg;
if (CP_TYPE_VOLATILE_P (ttl) && decl)
msg = "initialization of volatile reference type `%#T' from rvalue of type `%T'";
else if (CP_TYPE_VOLATILE_P (ttl))
msg = "conversion to volatile reference type `%#T' from rvalue of type `%T'";
else if (decl)
msg = "initialization of non-const reference type `%#T' from rvalue of type `%T'";
else
msg = "conversion to non-const reference type `%#T' from rvalue of type `%T'";
pedwarn (msg, reftype, intype);
}
}
/* For C++: Only need to do one-level references, but cannot
get tripped up on signed/unsigned differences.
DECL is either NULL_TREE or the _DECL node for a reference that is being
initialized. It can be error_mark_node if we don't know the _DECL but
we know it's an initialization. */
tree
convert_to_reference (reftype, expr, convtype, flags, decl)
tree reftype, expr;
int convtype, flags;
tree decl;
{
register tree type = TYPE_MAIN_VARIANT (TREE_TYPE (reftype));
register tree intype = TREE_TYPE (expr);
tree rval = NULL_TREE;
tree rval_as_conversion = NULL_TREE;
int i;
if (TREE_CODE (type) == FUNCTION_TYPE && intype == unknown_type_node)
{
expr = instantiate_type (type, expr,
(flags & LOOKUP_COMPLAIN)
? itf_complain : itf_none);
if (expr == error_mark_node)
return error_mark_node;
intype = TREE_TYPE (expr);
}
my_friendly_assert (TREE_CODE (intype) != REFERENCE_TYPE, 364);
intype = TYPE_MAIN_VARIANT (intype);
i = comp_target_types (type, intype, 0);
if (i <= 0 && (convtype & CONV_IMPLICIT) && IS_AGGR_TYPE (intype)
&& ! (flags & LOOKUP_NO_CONVERSION))
{
/* Look for a user-defined conversion to lvalue that we can use. */
rval_as_conversion
= build_type_conversion (reftype, expr, 1);
if (rval_as_conversion && rval_as_conversion != error_mark_node
&& real_lvalue_p (rval_as_conversion))
{
expr = rval_as_conversion;
rval_as_conversion = NULL_TREE;
intype = type;
i = 1;
}
}
if (((convtype & CONV_STATIC) && i == -1)
|| ((convtype & CONV_IMPLICIT) && i == 1))
{
if (flags & LOOKUP_COMPLAIN)
{
tree ttl = TREE_TYPE (reftype);
tree ttr = lvalue_type (expr);
if (! real_lvalue_p (expr))
warn_ref_binding (reftype, intype, decl);
if (! (convtype & CONV_CONST)
&& !at_least_as_qualified_p (ttl, ttr))
pedwarn ("conversion from `%T' to `%T' discards qualifiers",
ttr, reftype);
}
return build_up_reference (reftype, expr, flags, decl);
}
else if ((convtype & CONV_REINTERPRET) && lvalue_p (expr))
{
/* When casting an lvalue to a reference type, just convert into
a pointer to the new type and deference it. This is allowed
by San Diego WP section 5.2.9 paragraph 12, though perhaps it
should be done directly (jason). (int &)ri ---> *(int*)&ri */
/* B* bp; A& ar = (A&)bp; is valid, but it's probably not what they
meant. */
if (TREE_CODE (intype) == POINTER_TYPE
&& (comptypes (TREE_TYPE (intype), type,
COMPARE_BASE | COMPARE_RELAXED )))
warning ("casting `%T' to `%T' does not dereference pointer",
intype, reftype);
rval = build_unary_op (ADDR_EXPR, expr, 0);
if (rval != error_mark_node)
rval = convert_force (build_pointer_type (TREE_TYPE (reftype)),
rval, 0);
if (rval != error_mark_node)
rval = build1 (NOP_EXPR, reftype, rval);
}
else
{
rval = convert_for_initialization (NULL_TREE, type, expr, flags,
"converting", 0, 0);
if (rval == NULL_TREE || rval == error_mark_node)
return rval;
warn_ref_binding (reftype, intype, decl);
rval = build_up_reference (reftype, rval, flags, decl);
}
if (rval)
{
/* If we found a way to convert earlier, then use it. */
return rval;
}
my_friendly_assert (TREE_CODE (intype) != OFFSET_TYPE, 189);
if (flags & LOOKUP_COMPLAIN)
error ("cannot convert type `%T' to type `%T'", intype, reftype);
if (flags & LOOKUP_SPECULATIVELY)
return NULL_TREE;
return error_mark_node;
}
/* We are using a reference VAL for its value. Bash that reference all the
way down to its lowest form. */
tree
convert_from_reference (val)
tree val;
{
tree type = TREE_TYPE (val);
if (TREE_CODE (type) == OFFSET_TYPE)
type = TREE_TYPE (type);
if (TREE_CODE (type) == REFERENCE_TYPE)
return build_indirect_ref (val, NULL);
return val;
}
/* Implicitly convert the lvalue EXPR to another lvalue of type TOTYPE,
preserving cv-qualification. */
tree
convert_lvalue (totype, expr)
tree totype, expr;
{
totype = cp_build_qualified_type (totype, TYPE_QUALS (TREE_TYPE (expr)));
totype = build_reference_type (totype);
expr = convert_to_reference (totype, expr, CONV_IMPLICIT, LOOKUP_NORMAL,
NULL_TREE);
return convert_from_reference (expr);
}
/* C++ conversions, preference to static cast conversions. */
tree
cp_convert (type, expr)
tree type, expr;
{
return ocp_convert (type, expr, CONV_OLD_CONVERT, LOOKUP_NORMAL);
}
/* Conversion...
FLAGS indicates how we should behave. */
tree
ocp_convert (type, expr, convtype, flags)
tree type, expr;
int convtype, flags;
{
register tree e = expr;
register enum tree_code code = TREE_CODE (type);
if (e == error_mark_node
|| TREE_TYPE (e) == error_mark_node)
return error_mark_node;
complete_type (type);
complete_type (TREE_TYPE (expr));
e = decl_constant_value (e);
if (IS_AGGR_TYPE (type) && (convtype & CONV_FORCE_TEMP)
/* Some internal structures (vtable_entry_type, sigtbl_ptr_type)
don't go through finish_struct, so they don't have the synthesized
constructors. So don't force a temporary. */
&& TYPE_HAS_CONSTRUCTOR (type))
/* We need a new temporary; don't take this shortcut. */;
else if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (e)))
{
if (same_type_p (type, TREE_TYPE (e)))
/* The call to fold will not always remove the NOP_EXPR as
might be expected, since if one of the types is a typedef;
the comparsion in fold is just equality of pointers, not a
call to comptypes. We don't call fold in this case because
that can result in infinite recursion; fold will call
convert, which will call ocp_convert, etc. */
return e;
/* For complex data types, we need to perform componentwise
conversion. */
else if (TREE_CODE (type) == COMPLEX_TYPE)
return fold (convert_to_complex (type, e));
else
return fold (build1 (NOP_EXPR, type, e));
}
if (code == VOID_TYPE && (convtype & CONV_STATIC))
{
e = convert_to_void (e, /*implicit=*/NULL);
return e;
}
/* Just convert to the type of the member. */
if (code == OFFSET_TYPE)
{
type = TREE_TYPE (type);
code = TREE_CODE (type);
}
if (TREE_CODE (e) == OFFSET_REF)
e = resolve_offset_ref (e);
if (INTEGRAL_CODE_P (code))
{
tree intype = TREE_TYPE (e);
/* enum = enum, enum = int, enum = float, (enum)pointer are all
errors. */
if (TREE_CODE (type) == ENUMERAL_TYPE
&& ((ARITHMETIC_TYPE_P (intype) && ! (convtype & CONV_STATIC))
|| (TREE_CODE (intype) == POINTER_TYPE)))
{
pedwarn ("conversion from `%#T' to `%#T'", intype, type);
if (flag_pedantic_errors)
return error_mark_node;
}
if (IS_AGGR_TYPE (intype))
{
tree rval;
rval = build_type_conversion (type, e, 1);
if (rval)
return rval;
if (flags & LOOKUP_COMPLAIN)
error ("`%#T' used where a `%T' was expected", intype, type);
if (flags & LOOKUP_SPECULATIVELY)
return NULL_TREE;
return error_mark_node;
}
if (code == BOOLEAN_TYPE)
{
tree fn = NULL_TREE;
/* Common Ada/Pascal programmer's mistake. We always warn
about this since it is so bad. */
if (TREE_CODE (expr) == FUNCTION_DECL)
fn = expr;
else if (TREE_CODE (expr) == ADDR_EXPR
&& TREE_CODE (TREE_OPERAND (expr, 0)) == FUNCTION_DECL)
fn = TREE_OPERAND (expr, 0);
if (fn && !DECL_WEAK (fn))
warning ("the address of `%D', will always be `true'", fn);
return cp_truthvalue_conversion (e);
}
return fold (convert_to_integer (type, e));
}
if (code == POINTER_TYPE || code == REFERENCE_TYPE
|| TYPE_PTRMEMFUNC_P (type))
return fold (cp_convert_to_pointer (type, e, 0));
if (code == VECTOR_TYPE)
return fold (convert_to_vector (type, e));
if (code == REAL_TYPE || code == COMPLEX_TYPE)
{
if (IS_AGGR_TYPE (TREE_TYPE (e)))
{
tree rval;
rval = build_type_conversion (type, e, 1);
if (rval)
return rval;
else
if (flags & LOOKUP_COMPLAIN)
error ("`%#T' used where a floating point value was expected",
TREE_TYPE (e));
}
if (code == REAL_TYPE)
return fold (convert_to_real (type, e));
else if (code == COMPLEX_TYPE)
return fold (convert_to_complex (type, e));
}
/* New C++ semantics: since assignment is now based on
memberwise copying, if the rhs type is derived from the
lhs type, then we may still do a conversion. */
if (IS_AGGR_TYPE_CODE (code))
{
tree dtype = TREE_TYPE (e);
tree ctor = NULL_TREE;
dtype = TYPE_MAIN_VARIANT (dtype);
/* Conversion between aggregate types. New C++ semantics allow
objects of derived type to be cast to objects of base type.
Old semantics only allowed this between pointers.
There may be some ambiguity between using a constructor
vs. using a type conversion operator when both apply. */
ctor = e;
if (abstract_virtuals_error (NULL_TREE, type))
return error_mark_node;
if ((flags & LOOKUP_ONLYCONVERTING)
&& ! (IS_AGGR_TYPE (dtype) && DERIVED_FROM_P (type, dtype)))
/* For copy-initialization, first we create a temp of the proper type
with a user-defined conversion sequence, then we direct-initialize
the target with the temp (see [dcl.init]). */
ctor = build_user_type_conversion (type, ctor, flags);
else
ctor = build_method_call (NULL_TREE,
complete_ctor_identifier,
build_tree_list (NULL_TREE, ctor),
TYPE_BINFO (type), flags);
if (ctor)
return build_cplus_new (type, ctor);
}
/* If TYPE or TREE_TYPE (E) is not on the permanent_obstack,
then it won't be hashed and hence compare as not equal,
even when it is. */
if (code == ARRAY_TYPE
&& TREE_TYPE (TREE_TYPE (e)) == TREE_TYPE (type)
&& index_type_equal (TYPE_DOMAIN (TREE_TYPE (e)), TYPE_DOMAIN (type)))
return e;
if (flags & LOOKUP_COMPLAIN)
error ("conversion from `%T' to non-scalar type `%T' requested",
TREE_TYPE (expr), type);
if (flags & LOOKUP_SPECULATIVELY)
return NULL_TREE;
return error_mark_node;
}
/* When an expression is used in a void context, its value is discarded and
no lvalue-rvalue and similar conversions happen [expr.static.cast/4,
stmt.expr/1, expr.comma/1]. This permits dereferencing an incomplete type
in a void context. The C++ standard does not define what an `access' to an
object is, but there is reason to beleive that it is the lvalue to rvalue
conversion -- if it were not, `*&*p = 1' would violate [expr]/4 in that it
accesses `*p' not to calculate the value to be stored. But, dcl.type.cv/8
indicates that volatile semantics should be the same between C and C++
where ever possible. C leaves it implementation defined as to what
constitutes an access to a volatile. So, we interpret `*vp' as a read of
the volatile object `vp' points to, unless that is an incomplete type. For
volatile references we do not do this interpretation, because that would
make it impossible to ignore the reference return value from functions. We
issue warnings in the confusing cases.
IMPLICIT is tells us the context of an implicit void conversion. */
tree
convert_to_void (expr, implicit)
tree expr;
const char *implicit;
{
if (expr == error_mark_node
|| TREE_TYPE (expr) == error_mark_node)
return error_mark_node;
if (!TREE_TYPE (expr))
return expr;
if (VOID_TYPE_P (TREE_TYPE (expr)))
return expr;
switch (TREE_CODE (expr))
{
case COND_EXPR:
{
/* The two parts of a cond expr might be separate lvalues. */
tree op1 = TREE_OPERAND (expr,1);
tree op2 = TREE_OPERAND (expr,2);
tree new_op1 = convert_to_void (op1, implicit);
tree new_op2 = convert_to_void (op2, implicit);
expr = build (COND_EXPR, void_type_node,
TREE_OPERAND (expr, 0), new_op1, new_op2);
break;
}
case COMPOUND_EXPR:
{
/* The second part of a compound expr contains the value. */
tree op1 = TREE_OPERAND (expr,1);
tree new_op1 = convert_to_void (op1, implicit);
if (new_op1 != op1)
{
tree t = build (COMPOUND_EXPR, TREE_TYPE (new_op1),
TREE_OPERAND (expr, 0), new_op1);
TREE_SIDE_EFFECTS (t) = TREE_SIDE_EFFECTS (expr);
expr = t;
}
break;
}
case NON_LVALUE_EXPR:
case NOP_EXPR:
/* These have already decayed to rvalue. */
break;
case CALL_EXPR: /* we have a special meaning for volatile void fn() */
break;
case INDIRECT_REF:
{
tree type = TREE_TYPE (expr);
int is_reference = TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0)))
== REFERENCE_TYPE;
int is_volatile = TYPE_VOLATILE (type);
int is_complete = COMPLETE_TYPE_P (complete_type (type));
if (is_volatile && !is_complete)
warning ("object of incomplete type `%T' will not be accessed in %s",
type, implicit ? implicit : "void context");
else if (is_reference && is_volatile)
warning ("object of type `%T' will not be accessed in %s",
TREE_TYPE (TREE_OPERAND (expr, 0)),
implicit ? implicit : "void context");
if (is_reference || !is_volatile || !is_complete)
expr = TREE_OPERAND (expr, 0);
break;
}
case VAR_DECL:
{
/* External variables might be incomplete. */
tree type = TREE_TYPE (expr);
int is_complete = COMPLETE_TYPE_P (complete_type (type));
if (TYPE_VOLATILE (type) && !is_complete)
warning ("object `%E' of incomplete type `%T' will not be accessed in %s",
expr, type, implicit ? implicit : "void context");
break;
}
case OFFSET_REF:
expr = resolve_offset_ref (expr);
break;
default:;
}
{
tree probe = expr;
if (TREE_CODE (probe) == ADDR_EXPR)
probe = TREE_OPERAND (expr, 0);
if (type_unknown_p (probe))
{
/* [over.over] enumerates the places where we can take the address
of an overloaded function, and this is not one of them. */
pedwarn ("%s cannot resolve address of overloaded function",
implicit ? implicit : "void cast");
}
else if (implicit && probe == expr && is_overloaded_fn (probe))
/* Only warn when there is no &. */
warning ("%s is a reference, not call, to function `%E'",
implicit, expr);
}
if (expr != error_mark_node && !VOID_TYPE_P (TREE_TYPE (expr)))
{
/* FIXME: This is where we should check for expressions with no
effects. At the moment we do that in both build_x_component_expr
and expand_expr_stmt -- inconsistently too. For the moment
leave implicit void conversions unadorned so that expand_expr_stmt
has a chance of detecting some of the cases. */
if (!implicit)
expr = build1 (CONVERT_EXPR, void_type_node, expr);
}
return expr;
}
/* Create an expression whose value is that of EXPR,
converted to type TYPE. The TREE_TYPE of the value
is always TYPE. This function implements all reasonable
conversions; callers should filter out those that are
not permitted by the language being compiled.
Most of this routine is from build_reinterpret_cast.
The backend cannot call cp_convert (what was convert) because
conversions to/from basetypes may involve memory references
(vbases) and adding or subtracting small values (multiple
inheritance), but it calls convert from the constant folding code
on subtrees of already built trees after it has ripped them apart.
Also, if we ever support range variables, we'll probably also have to
do a little bit more work. */
tree
convert (type, expr)
tree type, expr;
{
tree intype;
if (type == error_mark_node || expr == error_mark_node)
return error_mark_node;
intype = TREE_TYPE (expr);
if (POINTER_TYPE_P (type) && POINTER_TYPE_P (intype))
{
expr = decl_constant_value (expr);
return fold (build1 (NOP_EXPR, type, expr));
}
return ocp_convert (type, expr, CONV_OLD_CONVERT,
LOOKUP_NORMAL|LOOKUP_NO_CONVERSION);
}
/* Like cp_convert, except permit conversions to take place which
are not normally allowed due to access restrictions
(such as conversion from sub-type to private super-type). */
tree
convert_force (type, expr, convtype)
tree type;
tree expr;
int convtype;
{
register tree e = expr;
register enum tree_code code = TREE_CODE (type);
if (code == REFERENCE_TYPE)
return fold (convert_to_reference (type, e, CONV_C_CAST, LOOKUP_COMPLAIN,
NULL_TREE));
else if (TREE_CODE (TREE_TYPE (e)) == REFERENCE_TYPE)
e = convert_from_reference (e);
if (code == POINTER_TYPE)
return fold (convert_to_pointer_force (type, e));
/* From typeck.c convert_for_assignment */
if (((TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE && TREE_CODE (e) == ADDR_EXPR
&& TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE
&& TREE_CODE (TREE_TYPE (TREE_TYPE (e))) == METHOD_TYPE)
|| integer_zerop (e)
|| TYPE_PTRMEMFUNC_P (TREE_TYPE (e)))
&& TYPE_PTRMEMFUNC_P (type))
{
/* compatible pointer to member functions. */
return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), e, 1);
}
return ocp_convert (type, e, CONV_C_CAST|convtype, LOOKUP_NORMAL);
}
/* Convert an aggregate EXPR to type XTYPE. If a conversion
exists, return the attempted conversion. This may
return ERROR_MARK_NODE if the conversion is not
allowed (references private members, etc).
If no conversion exists, NULL_TREE is returned.
If (FOR_SURE & 1) is non-zero, then we allow this type conversion
to take place immediately. Otherwise, we build a SAVE_EXPR
which can be evaluated if the results are ever needed.
Changes to this functions should be mirrored in user_harshness.
FIXME: Ambiguity checking is wrong. Should choose one by the implicit
object parameter, or by the second standard conversion sequence if
that doesn't do it. This will probably wait for an overloading rewrite.
(jason 8/9/95) */
tree
build_type_conversion (xtype, expr, for_sure)
tree xtype, expr;
int for_sure;
{
/* C++: check to see if we can convert this aggregate type
into the required type. */
return build_user_type_conversion
(xtype, expr, for_sure ? LOOKUP_NORMAL : 0);
}
/* Convert the given EXPR to one of a group of types suitable for use in an
expression. DESIRES is a combination of various WANT_* flags (q.v.)
which indicates which types are suitable. If COMPLAIN is 1, complain
about ambiguity; otherwise, the caller will deal with it. */
tree
build_expr_type_conversion (desires, expr, complain)
int desires;
tree expr;
int complain;
{
tree basetype = TREE_TYPE (expr);
tree conv = NULL_TREE;
tree winner = NULL_TREE;
if (expr == null_node
&& (desires & WANT_INT)
&& !(desires & WANT_NULL))
warning ("converting NULL to non-pointer type");
if (TREE_CODE (expr) == OFFSET_REF)
expr = resolve_offset_ref (expr);
expr = convert_from_reference (expr);
basetype = TREE_TYPE (expr);
if (basetype == error_mark_node)
return error_mark_node;
if (! IS_AGGR_TYPE (basetype))
switch (TREE_CODE (basetype))
{
case INTEGER_TYPE:
if ((desires & WANT_NULL) && null_ptr_cst_p (expr))
return expr;
/* else fall through... */
case BOOLEAN_TYPE:
return (desires & WANT_INT) ? expr : NULL_TREE;
case ENUMERAL_TYPE:
return (desires & WANT_ENUM) ? expr : NULL_TREE;
case REAL_TYPE:
return (desires & WANT_FLOAT) ? expr : NULL_TREE;
case POINTER_TYPE:
return (desires & WANT_POINTER) ? expr : NULL_TREE;
case FUNCTION_TYPE:
case ARRAY_TYPE:
return (desires & WANT_POINTER) ? default_conversion (expr)
: NULL_TREE;
default:
return NULL_TREE;
}
/* The code for conversions from class type is currently only used for
delete expressions. Other expressions are handled by build_new_op. */
if (! TYPE_HAS_CONVERSION (basetype))
return NULL_TREE;
for (conv = lookup_conversions (basetype); conv; conv = TREE_CHAIN (conv))
{
int win = 0;
tree candidate;
tree cand = TREE_VALUE (conv);
if (winner && winner == cand)
continue;
candidate = TREE_TYPE (TREE_TYPE (cand));
if (TREE_CODE (candidate) == REFERENCE_TYPE)
candidate = TREE_TYPE (candidate);
switch (TREE_CODE (candidate))
{
case BOOLEAN_TYPE:
case INTEGER_TYPE:
win = (desires & WANT_INT); break;
case ENUMERAL_TYPE:
win = (desires & WANT_ENUM); break;
case REAL_TYPE:
win = (desires & WANT_FLOAT); break;
case POINTER_TYPE:
win = (desires & WANT_POINTER); break;
default:
break;
}
if (win)
{
if (winner)
{
if (complain)
{
error ("ambiguous default type conversion from `%T'",
basetype);
error (" candidate conversions include `%D' and `%D'",
winner, cand);
}
return error_mark_node;
}
else
winner = cand;
}
}
if (winner)
{
tree type = TREE_TYPE (TREE_TYPE (winner));
if (TREE_CODE (type) == REFERENCE_TYPE)
type = TREE_TYPE (type);
return build_user_type_conversion (type, expr, LOOKUP_NORMAL);
}
return NULL_TREE;
}
/* Implements integral promotion (4.1) and float->double promotion. */
tree
type_promotes_to (type)
tree type;
{
int type_quals;
if (type == error_mark_node)
return error_mark_node;
type_quals = cp_type_quals (type);
type = TYPE_MAIN_VARIANT (type);
/* bool always promotes to int (not unsigned), even if it's the same
size. */
if (type == boolean_type_node)
type = integer_type_node;
/* Normally convert enums to int, but convert wide enums to something
wider. */
else if (TREE_CODE (type) == ENUMERAL_TYPE
|| type == wchar_type_node)
{
int precision = MAX (TYPE_PRECISION (type),
TYPE_PRECISION (integer_type_node));
tree totype = type_for_size (precision, 0);
if (TREE_UNSIGNED (type)
&& ! int_fits_type_p (TYPE_MAX_VALUE (type), totype))
type = type_for_size (precision, 1);
else
type = totype;
}
else if (c_promoting_integer_type_p (type))
{
/* Retain unsignedness if really not getting bigger. */
if (TREE_UNSIGNED (type)
&& TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node))
type = unsigned_type_node;
else
type = integer_type_node;
}
else if (type == float_type_node)
type = double_type_node;
return cp_build_qualified_type (type, type_quals);
}
/* The routines below this point are carefully written to conform to
the standard. They use the same terminology, and follow the rules
closely. Although they are used only in pt.c at the moment, they
should presumably be used everywhere in the future. */
/* Attempt to perform qualification conversions on EXPR to convert it
to TYPE. Return the resulting expression, or error_mark_node if
the conversion was impossible. */
tree
perform_qualification_conversions (type, expr)
tree type;
tree expr;
{
if (TREE_CODE (type) == POINTER_TYPE
&& TREE_CODE (TREE_TYPE (expr)) == POINTER_TYPE
&& comp_ptr_ttypes (TREE_TYPE (type), TREE_TYPE (TREE_TYPE (expr))))
return build1 (NOP_EXPR, type, expr);
else
return error_mark_node;
}