gcc/c-convert.c

   1 /* Language-level data type conversion for GNU C.
   2    Copyright (C) 1987, 1988, 1991, 1998, 2002, 2003, 2004, 2005
   3    Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 2, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15 for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING.  If not, write to the Free
  19 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  20 02110-1301, USA.  */
  21
  22
  23 /* This file contains the functions for converting C expressions
  24    to different data types.  The only entry point is `convert'.
  25    Every language front end must have a `convert' function
  26    but what kind of conversions it does will depend on the language.  */
  27
  28 #include "config.h"
  29 #include "system.h"
  30 #include "coretypes.h"
  31 #include "tm.h"
  32 #include "tree.h"
  33 #include "flags.h"
  34 #include "convert.h"
  35 #include "c-common.h"
  36 #include "c-tree.h"
  37 #include "langhooks.h"
  38 #include "toplev.h"
  39 #include "target.h"
  40
  41 /* Change of width--truncation and extension of integers or reals--
  42    is represented with NOP_EXPR.  Proper functioning of many things
  43    assumes that no other conversions can be NOP_EXPRs.
  44
  45    Conversion between integer and pointer is represented with CONVERT_EXPR.
  46    Converting integer to real uses FLOAT_EXPR
  47    and real to integer uses FIX_TRUNC_EXPR.
  48
  49    Here is a list of all the functions that assume that widening and
  50    narrowing is always done with a NOP_EXPR:
  51      In convert.c, convert_to_integer.
  52      In c-typeck.c, build_binary_op (boolean ops), and
  53         c_common_truthvalue_conversion.
  54      In expr.c: expand_expr, for operands of a MULT_EXPR.
  55      In fold-const.c: fold.
  56      In tree.c: get_narrower and get_unwidened.  */
  57 \f
  58 /* Subroutines of `convert'.  */
  59
  60
  61 \f
  62 /* Create an expression whose value is that of EXPR,
  63    converted to type TYPE.  The TREE_TYPE of the value
  64    is always TYPE.  This function implements all reasonable
  65    conversions; callers should filter out those that are
  66    not permitted by the language being compiled.  */
  67
  68 tree
  69 convert (tree type, tree expr)
  70 {
  71   tree e = expr;
  72   enum tree_code code = TREE_CODE (type);
  73   const char *invalid_conv_diag;
  74
  75   if (type == error_mark_node
  76       || expr == error_mark_node
  77       || TREE_TYPE (expr) == error_mark_node)
  78     return error_mark_node;
  79
  80   if ((invalid_conv_diag
  81        = targetm.invalid_conversion (TREE_TYPE (expr), type)))
  82     {
  83       error (invalid_conv_diag);
  84       return error_mark_node;
  85     }
  86
  87   if (type == TREE_TYPE (expr))
  88     return expr;
  89
  90   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)))
  91     return fold_build1 (NOP_EXPR, type, expr);
  92   if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
  93     return error_mark_node;
  94   if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
  95     {
  96       error ("void value not ignored as it ought to be");
  97       return error_mark_node;
  98     }
  99   if (code == VOID_TYPE)
 100     return build1 (CONVERT_EXPR, type, e);
 101 #if 0
 102   /* This is incorrect.  A truncation can't be stripped this way.
 103      Extensions will be stripped by the use of get_unwidened.  */
 104   if (TREE_CODE (expr) == NOP_EXPR)
 105     return convert (type, TREE_OPERAND (expr, 0));
 106 #endif
 107   if (code == INTEGER_TYPE || code == ENUMERAL_TYPE)
 108     return fold (convert_to_integer (type, e));
 109   if (code == BOOLEAN_TYPE)
 110     {
 111       tree t = c_objc_common_truthvalue_conversion (expr);
 112       if (TREE_CODE (t) == ERROR_MARK)
 113         return t;
 114
 115       /* If it returns a NOP_EXPR, we must fold it here to avoid
 116          infinite recursion between fold () and convert ().  */
 117       if (TREE_CODE (t) == NOP_EXPR)
 118         return fold_build1 (NOP_EXPR, type, TREE_OPERAND (t, 0));
 119       else
 120         return fold_build1 (NOP_EXPR, type, t);
 121     }
 122   if (code == POINTER_TYPE || code == REFERENCE_TYPE)
 123     return fold (convert_to_pointer (type, e));
 124   if (code == REAL_TYPE)
 125     return fold (convert_to_real (type, e));
 126   if (code == COMPLEX_TYPE)
 127     return fold (convert_to_complex (type, e));
 128   if (code == VECTOR_TYPE)
 129     return fold (convert_to_vector (type, e));
 130   if ((code == RECORD_TYPE || code == UNION_TYPE)
 131       && lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
 132       return e;
 133
 134   error ("conversion to non-scalar type requested");
 135   return error_mark_node;
 136 }