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Annotation of GNUtools/cc/c-convert.c, revision 1.1

1.1     ! root        1: /* Language-level data type conversion for GNU C.
        !             2:    Copyright (C) 1987, 1988, 1991 Free Software Foundation, Inc.
        !             3: 
        !             4: This file is part of GNU CC.
        !             5: 
        !             6: GNU CC is free software; you can redistribute it and/or modify
        !             7: it under the terms of the GNU General Public License as published by
        !             8: the Free Software Foundation; either version 2, or (at your option)
        !             9: any later version.
        !            10: 
        !            11: GNU CC is distributed in the hope that it will be useful,
        !            12: but WITHOUT ANY WARRANTY; without even the implied warranty of
        !            13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
        !            14: GNU General Public License for more details.
        !            15: 
        !            16: You should have received a copy of the GNU General Public License
        !            17: along with GNU CC; see the file COPYING.  If not, write to
        !            18: the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
        !            19: 
        !            20: 
        !            21: /* This file contains the functions for converting C expressions
        !            22:    to different data types.  The only entry point is `convert'.
        !            23:    Every language front end must have a `convert' function
        !            24:    but what kind of conversions it does will depend on the language.  */
        !            25: 
        !            26: #include "config.h"
        !            27: #include "tree.h"
        !            28: #include "flags.h"
        !            29: #include "convert.h"
        !            30: 
        !            31: /* Change of width--truncation and extension of integers or reals--
        !            32:    is represented with NOP_EXPR.  Proper functioning of many things
        !            33:    assumes that no other conversions can be NOP_EXPRs.
        !            34: 
        !            35:    Conversion between integer and pointer is represented with CONVERT_EXPR.
        !            36:    Converting integer to real uses FLOAT_EXPR
        !            37:    and real to integer uses FIX_TRUNC_EXPR.
        !            38: 
        !            39:    Here is a list of all the functions that assume that widening and
        !            40:    narrowing is always done with a NOP_EXPR:
        !            41:      In convert.c, convert_to_integer.
        !            42:      In c-typeck.c, build_binary_op (boolean ops), and truthvalue_conversion.
        !            43:      In expr.c: expand_expr, for operands of a MULT_EXPR.
        !            44:      In fold-const.c: fold.
        !            45:      In tree.c: get_narrower and get_unwidened.  */
        !            46: 
        !            47: /* Subroutines of `convert'.  */
        !            48: 
        !            49: 
        !            50: 
        !            51: /* Create an expression whose value is that of EXPR,
        !            52:    converted to type TYPE.  The TREE_TYPE of the value
        !            53:    is always TYPE.  This function implements all reasonable
        !            54:    conversions; callers should filter out those that are
        !            55:    not permitted by the language being compiled.  */
        !            56: 
        !            57: tree
        !            58: convert (type, expr)
        !            59:      tree type, expr;
        !            60: {
        !            61:   register tree e = expr;
        !            62:   register enum tree_code code = TREE_CODE (type);
        !            63: 
        !            64:   if (type == TREE_TYPE (expr)
        !            65:       || TREE_CODE (expr) == ERROR_MARK)
        !            66:     return expr;
        !            67:   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)))
        !            68:     return fold (build1 (NOP_EXPR, type, expr));
        !            69:   if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
        !            70:     return error_mark_node;
        !            71:   if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
        !            72:     {
        !            73:       error ("void value not ignored as it ought to be");
        !            74:       return error_mark_node;
        !            75:     }
        !            76:   if (code == VOID_TYPE)
        !            77:     return build1 (CONVERT_EXPR, type, e);
        !            78: #if 0
        !            79:   /* This is incorrect.  A truncation can't be stripped this way.
        !            80:      Extensions will be stripped by the use of get_unwidened.  */
        !            81:   if (TREE_CODE (expr) == NOP_EXPR)
        !            82:     return convert (type, TREE_OPERAND (expr, 0));
        !            83: #endif
        !            84:   if (code == INTEGER_TYPE || code == ENUMERAL_TYPE)
        !            85:     return fold (convert_to_integer (type, e));
        !            86:   if (code == POINTER_TYPE)
        !            87:     return fold (convert_to_pointer (type, e));
        !            88:   if (code == REAL_TYPE)
        !            89:     return fold (convert_to_real (type, e));
        !            90:   if (code == COMPLEX_TYPE)
        !            91:     return fold (convert_to_complex (type, e));
        !            92: 
        !            93:   error ("conversion to non-scalar type requested");
        !            94:   return error_mark_node;
        !            95: }

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