1 /* Language-level data type conversion for GNU C. 2 Copyright (C) 1987, 1988, 1991, 1998, 2002 Free Software Foundation, Inc. 3 4 This file is part of GCC. 5 6 GCC is free software; you can redistribute it and/or modify it under 7 the terms of the GNU General Public License as published by the Free 8 Software Foundation; either version 2, or (at your option) any later 9 version. 10 11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY 12 WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with GCC; see the file COPYING. If not, write to the Free 18 Software Foundation, 59 Temple Place - Suite 330, Boston, MA 19 02111-1307, USA. */ 20 21 22 /* This file contains the functions for converting C expressions 23 to different data types. The only entry point is `convert'. 24 Every language front end must have a `convert' function 25 but what kind of conversions it does will depend on the language. */ 26 27 #include "config.h" 28 #include "system.h" 29 #include "tree.h" 30 #include "flags.h" 31 #include "convert.h" 32 #include "c-common.h" 33 #include "toplev.h" 34 35 /* Change of width--truncation and extension of integers or reals-- 36 is represented with NOP_EXPR. Proper functioning of many things 37 assumes that no other conversions can be NOP_EXPRs. 38 39 Conversion between integer and pointer is represented with CONVERT_EXPR. 40 Converting integer to real uses FLOAT_EXPR 41 and real to integer uses FIX_TRUNC_EXPR. 42 43 Here is a list of all the functions that assume that widening and 44 narrowing is always done with a NOP_EXPR: 45 In convert.c, convert_to_integer. 46 In c-typeck.c, build_binary_op (boolean ops), and 47 c_common_truthvalue_conversion. 48 In expr.c: expand_expr, for operands of a MULT_EXPR. 49 In fold-const.c: fold. 50 In tree.c: get_narrower and get_unwidened. */ 51 52 /* Subroutines of `convert'. */ 53 54 55 56 /* Create an expression whose value is that of EXPR, 57 converted to type TYPE. The TREE_TYPE of the value 58 is always TYPE. This function implements all reasonable 59 conversions; callers should filter out those that are 60 not permitted by the language being compiled. */ 61 62 tree 63 convert (type, expr) 64 tree type, expr; 65 { 66 tree e = expr; 67 enum tree_code code = TREE_CODE (type); 68 69 if (type == TREE_TYPE (expr) 70 || TREE_CODE (expr) == ERROR_MARK 71 || code == ERROR_MARK || TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK) 72 return expr; 73 74 if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr))) 75 return fold (build1 (NOP_EXPR, type, expr)); 76 if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK) 77 return error_mark_node; 78 if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE) 79 { 80 error ("void value not ignored as it ought to be"); 81 return error_mark_node; 82 } 83 if (code == VOID_TYPE) 84 return build1 (CONVERT_EXPR, type, e); 85 #if 0 86 /* This is incorrect. A truncation can't be stripped this way. 87 Extensions will be stripped by the use of get_unwidened. */ 88 if (TREE_CODE (expr) == NOP_EXPR) 89 return convert (type, TREE_OPERAND (expr, 0)); 90 #endif 91 if (code == INTEGER_TYPE || code == ENUMERAL_TYPE) 92 return fold (convert_to_integer (type, e)); 93 if (code == BOOLEAN_TYPE) 94 { 95 tree t = c_common_truthvalue_conversion (expr); 96 /* If it returns a NOP_EXPR, we must fold it here to avoid 97 infinite recursion between fold () and convert (). */ 98 if (TREE_CODE (t) == NOP_EXPR) 99 return fold (build1 (NOP_EXPR, type, TREE_OPERAND (t, 0))); 100 else 101 return fold (build1 (NOP_EXPR, type, t)); 102 } 103 if (code == POINTER_TYPE || code == REFERENCE_TYPE) 104 return fold (convert_to_pointer (type, e)); 105 if (code == REAL_TYPE) 106 return fold (convert_to_real (type, e)); 107 if (code == COMPLEX_TYPE) 108 return fold (convert_to_complex (type, e)); 109 if (code == VECTOR_TYPE) 110 return fold (convert_to_vector (type, e)); 111 112 error ("conversion to non-scalar type requested"); 113 return error_mark_node; 114 } 115