static tree lookup_field (tree, tree);
static tree convert_arguments (tree, tree, tree, tree);
static tree pointer_diff (tree, tree);
-static tree unary_complex_lvalue (enum tree_code, tree, int);
-static void pedantic_lvalue_warning (enum tree_code);
static tree internal_build_compound_expr (tree, int);
static tree convert_for_assignment (tree, tree, const char *, tree, tree,
int);
tree ref;
/* If DATUM is a COMPOUND_EXPR, move our reference inside it.
- If pedantic ensure that the arguments are not lvalues; otherwise,
+ Ensure that the arguments are not lvalues; otherwise,
if the component is an array, it would wrongly decay to a pointer in
C89 mode.
We cannot do this with a COND_EXPR, because in a conditional expression
{
tree value = build_component_ref (TREE_OPERAND (datum, 1), component);
return build (COMPOUND_EXPR, TREE_TYPE (value),
- TREE_OPERAND (datum, 0), pedantic_non_lvalue (value));
+ TREE_OPERAND (datum, 0), non_lvalue (value));
}
default:
break;
case POSTINCREMENT_EXPR:
case PREDECREMENT_EXPR:
case POSTDECREMENT_EXPR:
- /* Handle complex lvalues (when permitted)
- by reduction to simpler cases. */
-
- val = unary_complex_lvalue (code, arg, 0);
- if (val != 0)
- return val;
/* Increment or decrement the real part of the value,
and don't change the imaginary part. */
inc = convert (argtype, inc);
- /* Handle incrementing a cast-expression. */
-
- while (1)
- switch (TREE_CODE (arg))
- {
- case NOP_EXPR:
- case CONVERT_EXPR:
- case FLOAT_EXPR:
- case FIX_TRUNC_EXPR:
- case FIX_FLOOR_EXPR:
- case FIX_ROUND_EXPR:
- case FIX_CEIL_EXPR:
- pedantic_lvalue_warning (CONVERT_EXPR);
- /* If the real type has the same machine representation
- as the type it is cast to, we can make better output
- by adding directly to the inside of the cast. */
- if ((TREE_CODE (TREE_TYPE (arg))
- == TREE_CODE (TREE_TYPE (TREE_OPERAND (arg, 0))))
- && (TYPE_MODE (TREE_TYPE (arg))
- == TYPE_MODE (TREE_TYPE (TREE_OPERAND (arg, 0)))))
- arg = TREE_OPERAND (arg, 0);
- else
- {
- tree incremented, modify, value;
- if (TREE_CODE (TREE_TYPE (arg)) == BOOLEAN_TYPE)
- value = boolean_increment (code, arg);
- else
- {
- arg = stabilize_reference (arg);
- if (code == PREINCREMENT_EXPR || code == PREDECREMENT_EXPR)
- value = arg;
- else
- value = save_expr (arg);
- incremented = build (((code == PREINCREMENT_EXPR
- || code == POSTINCREMENT_EXPR)
- ? PLUS_EXPR : MINUS_EXPR),
- argtype, value, inc);
- TREE_SIDE_EFFECTS (incremented) = 1;
- modify = build_modify_expr (arg, NOP_EXPR, incremented);
- value = build (COMPOUND_EXPR, TREE_TYPE (arg), modify, value);
- }
- TREE_USED (value) = 1;
- return value;
- }
- break;
-
- default:
- goto give_up;
- }
- give_up:
-
/* Complain about anything else that is not a true lvalue. */
if (!lvalue_or_else (arg, ((code == PREINCREMENT_EXPR
|| code == POSTINCREMENT_EXPR)
TREE_OPERAND (arg, 1), 1);
}
- /* Handle complex lvalues (when permitted)
- by reduction to simpler cases. */
- val = unary_complex_lvalue (code, arg, flag);
- if (val != 0)
- return val;
-
/* Anything not already handled and not a true memory reference
or a non-lvalue array is an error. */
else if (typecode != FUNCTION_TYPE && !flag
return win;
}
-/* Apply unary lvalue-demanding operator CODE to the expression ARG
- for certain kinds of expressions which are not really lvalues
- but which we can accept as lvalues. If FLAG is nonzero, then
- non-lvalues are OK since we may be converting a non-lvalue array to
- a pointer in C99.
-
- If ARG is not a kind of expression we can handle, return zero. */
-
-static tree
-unary_complex_lvalue (enum tree_code code, tree arg, int flag)
-{
- /* Handle (a, b) used as an "lvalue". */
- if (TREE_CODE (arg) == COMPOUND_EXPR)
- {
- tree real_result = build_unary_op (code, TREE_OPERAND (arg, 1), 0);
-
- /* If this returns a function type, it isn't really being used as
- an lvalue, so don't issue a warning about it. */
- if (TREE_CODE (TREE_TYPE (arg)) != FUNCTION_TYPE && !flag)
- pedantic_lvalue_warning (COMPOUND_EXPR);
-
- return build (COMPOUND_EXPR, TREE_TYPE (real_result),
- TREE_OPERAND (arg, 0), real_result);
- }
-
- /* Handle (a ? b : c) used as an "lvalue". */
- if (TREE_CODE (arg) == COND_EXPR)
- {
- if (!flag)
- pedantic_lvalue_warning (COND_EXPR);
- if (TREE_CODE (TREE_TYPE (arg)) != FUNCTION_TYPE && !flag)
- pedantic_lvalue_warning (COMPOUND_EXPR);
-
- return (build_conditional_expr
- (TREE_OPERAND (arg, 0),
- build_unary_op (code, TREE_OPERAND (arg, 1), flag),
- build_unary_op (code, TREE_OPERAND (arg, 2), flag)));
- }
-
- return 0;
-}
-
-/* If pedantic, warn about improper lvalue. CODE is either COND_EXPR
- COMPOUND_EXPR, or CONVERT_EXPR (for casts). */
-
-static void
-pedantic_lvalue_warning (enum tree_code code)
-{
- switch (code)
- {
- case COND_EXPR:
- pedwarn ("use of conditional expressions as lvalues is deprecated");
- break;
- case COMPOUND_EXPR:
- pedwarn ("use of compound expressions as lvalues is deprecated");
- break;
- default:
- pedwarn ("use of cast expressions as lvalues is deprecated");
- break;
- }
-}
\f
/* Warn about storing in something that is `const'. */
op2 = convert_and_check (result_type, op2);
if (TREE_CODE (ifexp) == INTEGER_CST)
- return pedantic_non_lvalue (integer_zerop (ifexp) ? op2 : op1);
+ return non_lvalue (integer_zerop (ifexp) ? op2 : op1);
return fold (build (COND_EXPR, result_type, ifexp, op1, op2));
}
}
}
- /* Pedantically, don't let (void *) (FOO *) 0 be a null pointer constant. */
- if (pedantic && TREE_CODE (value) == INTEGER_CST
+ /* Don't let (void *) (FOO *) 0 be a null pointer constant. */
+ if (TREE_CODE (value) == INTEGER_CST
&& TREE_CODE (expr) == INTEGER_CST
&& TREE_CODE (TREE_TYPE (expr)) != INTEGER_TYPE)
value = non_lvalue (value);
- /* If pedantic, don't let a cast be an lvalue. */
- if (value == expr && pedantic)
+ /* Don't let a cast be an lvalue. */
+ if (value == expr)
value = non_lvalue (value);
return value;
newrhs = rhs;
- /* Handle control structure constructs used as "lvalues". */
-
- switch (TREE_CODE (lhs))
- {
- /* Handle (a, b) used as an "lvalue". */
- case COMPOUND_EXPR:
- pedantic_lvalue_warning (COMPOUND_EXPR);
- newrhs = build_modify_expr (TREE_OPERAND (lhs, 1), modifycode, rhs);
- if (TREE_CODE (newrhs) == ERROR_MARK)
- return error_mark_node;
- return build (COMPOUND_EXPR, lhstype,
- TREE_OPERAND (lhs, 0), newrhs);
-
- /* Handle (a ? b : c) used as an "lvalue". */
- case COND_EXPR:
- pedantic_lvalue_warning (COND_EXPR);
- rhs = save_expr (rhs);
- {
- /* Produce (a ? (b = rhs) : (c = rhs))
- except that the RHS goes through a save-expr
- so the code to compute it is only emitted once. */
- tree cond
- = build_conditional_expr (TREE_OPERAND (lhs, 0),
- build_modify_expr (TREE_OPERAND (lhs, 1),
- modifycode, rhs),
- build_modify_expr (TREE_OPERAND (lhs, 2),
- modifycode, rhs));
- if (TREE_CODE (cond) == ERROR_MARK)
- return cond;
- /* Make sure the code to compute the rhs comes out
- before the split. */
- return build (COMPOUND_EXPR, TREE_TYPE (lhs),
- /* But cast it to void to avoid an "unused" error. */
- convert (void_type_node, rhs), cond);
- }
- default:
- break;
- }
-
/* If a binary op has been requested, combine the old LHS value with the RHS
producing the value we should actually store into the LHS. */
newrhs = build_binary_op (modifycode, lhs, rhs, 1);
}
- /* Handle a cast used as an "lvalue".
- We have already performed any binary operator using the value as cast.
- Now convert the result to the cast type of the lhs,
- and then true type of the lhs and store it there;
- then convert result back to the cast type to be the value
- of the assignment. */
-
- switch (TREE_CODE (lhs))
- {
- case NOP_EXPR:
- case CONVERT_EXPR:
- case FLOAT_EXPR:
- case FIX_TRUNC_EXPR:
- case FIX_FLOOR_EXPR:
- case FIX_ROUND_EXPR:
- case FIX_CEIL_EXPR:
- newrhs = default_function_array_conversion (newrhs);
- {
- tree inner_lhs = TREE_OPERAND (lhs, 0);
- tree result;
- result = build_modify_expr (inner_lhs, NOP_EXPR,
- convert (TREE_TYPE (inner_lhs),
- convert (lhstype, newrhs)));
- if (TREE_CODE (result) == ERROR_MARK)
- return result;
- pedantic_lvalue_warning (CONVERT_EXPR);
- return convert (TREE_TYPE (lhs), result);
- }
-
- default:
- break;
- }
-
- /* Now we have handled acceptable kinds of LHS that are not truly lvalues.
- Reject anything strange now. */
-
if (!lvalue_or_else (lhs, "invalid lvalue in assignment"))
return error_mark_node;
* Nested Functions:: As in Algol and Pascal, lexical scoping of functions.
* Constructing Calls:: Dispatching a call to another function.
* Typeof:: @code{typeof}: referring to the type of an expression.
-* Lvalues:: Using @samp{?:}, @samp{,} and casts in lvalues.
* Conditionals:: Omitting the middle operand of a @samp{?:} expression.
* Long Long:: Double-word integers---@code{long long int}.
* Complex:: Data types for complex numbers.
@noindent
This will work with all versions of GCC@.
-@node Lvalues
-@section Generalized Lvalues
-@cindex compound expressions as lvalues
-@cindex expressions, compound, as lvalues
-@cindex conditional expressions as lvalues
-@cindex expressions, conditional, as lvalues
-@cindex casts as lvalues
-@cindex generalized lvalues
-@cindex lvalues, generalized
-@cindex extensions, @code{?:}
-@cindex @code{?:} extensions
-
-Compound expressions, conditional expressions and casts are allowed as
-lvalues provided their operands are lvalues. This means that you can take
-their addresses or store values into them. All these extensions are
-deprecated.
-
-Standard C++ allows compound expressions and conditional expressions
-as lvalues, and permits casts to reference type, so use of this
-extension is not supported for C++ code.
-
-For example, a compound expression can be assigned, provided the last
-expression in the sequence is an lvalue. These two expressions are
-equivalent:
-
-@smallexample
-(a, b) += 5
-a, (b += 5)
-@end smallexample
-
-Similarly, the address of the compound expression can be taken. These two
-expressions are equivalent:
-
-@smallexample
-&(a, b)
-a, &b
-@end smallexample
-
-A conditional expression is a valid lvalue if its type is not void and the
-true and false branches are both valid lvalues. For example, these two
-expressions are equivalent:
-
-@smallexample
-(a ? b : c) = 5
-(a ? b = 5 : (c = 5))
-@end smallexample
-
-A cast is a valid lvalue if its operand is an lvalue. This extension
-is deprecated. A simple
-assignment whose left-hand side is a cast works by converting the
-right-hand side first to the specified type, then to the type of the
-inner left-hand side expression. After this is stored, the value is
-converted back to the specified type to become the value of the
-assignment. Thus, if @code{a} has type @code{char *}, the following two
-expressions are equivalent:
-
-@smallexample
-(int)a = 5
-(int)(a = (char *)(int)5)
-@end smallexample
-
-An assignment-with-arithmetic operation such as @samp{+=} applied to a cast
-performs the arithmetic using the type resulting from the cast, and then
-continues as in the previous case. Therefore, these two expressions are
-equivalent:
-
-@smallexample
-(int)a += 5
-(int)(a = (char *)(int) ((int)a + 5))
-@end smallexample
-
-You cannot take the address of an lvalue cast, because the use of its
-address would not work out coherently. Suppose that @code{&(int)f} were
-permitted, where @code{f} has type @code{float}. Then the following
-statement would try to store an integer bit-pattern where a floating
-point number belongs:
-
-@smallexample
-*&(int)f = 1;
-@end smallexample
-
-This is quite different from what @code{(int)f = 1} would do---that
-would convert 1 to floating point and store it. Rather than cause this
-inconsistency, we think it is better to prohibit use of @samp{&} on a cast.
-
-If you really do want an @code{int *} pointer with the address of
-@code{f}, you can simply write @code{(int *)&f}.
-
@node Conditionals
@section Conditionals with Omitted Operands
@cindex conditional expressions, extensions
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