gcc/c-convert.c

   1 /* Language-level data type conversion for GNU C.
   2    Copyright (C) 1987, 1988, 1991, 1998, 2002, 2003, 2004
   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, 59 Temple Place - Suite 330, Boston, MA
  20 02111-1307, 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 "langhooks.h"
  37 #include "toplev.h"
  38
  39 /* Change of width--truncation and extension of integers or reals--
  40    is represented with NOP_EXPR.  Proper functioning of many things
  41    assumes that no other conversions can be NOP_EXPRs.
  42
  43    Conversion between integer and pointer is represented with CONVERT_EXPR.
  44    Converting integer to real uses FLOAT_EXPR
  45    and real to integer uses FIX_TRUNC_EXPR.
  46
  47    Here is a list of all the functions that assume that widening and
  48    narrowing is always done with a NOP_EXPR:
  49      In convert.c, convert_to_integer.
  50      In c-typeck.c, build_binary_op (boolean ops), and
  51         c_common_truthvalue_conversion.
  52      In expr.c: expand_expr, for operands of a MULT_EXPR.
  53      In fold-const.c: fold.
  54      In tree.c: get_narrower and get_unwidened.  */
  55 \f
  56 /* Subroutines of `convert'.  */
  57
  58
  59 \f
  60 /* Create an expression whose value is that of EXPR,
  61    converted to type TYPE.  The TREE_TYPE of the value
  62    is always TYPE.  This function implements all reasonable
  63    conversions; callers should filter out those that are
  64    not permitted by the language being compiled.  */
  65
  66 tree
  67 convert (tree type, tree expr)
  68 {
  69   tree e = expr;
  70   enum tree_code code = TREE_CODE (type);
  71
  72   if (type == TREE_TYPE (expr)
  73       || TREE_CODE (expr) == ERROR_MARK
  74       || code == ERROR_MARK || TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
  75     return expr;
  76
  77   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)))
  78     return fold (build1 (NOP_EXPR, type, expr));
  79   if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
  80     return error_mark_node;
  81   if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
  82     {
  83       error ("void value not ignored as it ought to be");
  84       return error_mark_node;
  85     }
  86   if (code == VOID_TYPE)
  87     return build1 (CONVERT_EXPR, type, e);
  88 #if 0
  89   /* This is incorrect.  A truncation can't be stripped this way.
  90      Extensions will be stripped by the use of get_unwidened.  */
  91   if (TREE_CODE (expr) == NOP_EXPR)
  92     return convert (type, TREE_OPERAND (expr, 0));
  93 #endif
  94   if (code == INTEGER_TYPE || code == ENUMERAL_TYPE)
  95     return fold (convert_to_integer (type, e));
  96   if (code == BOOLEAN_TYPE)
  97     {
  98       tree t = lang_hooks.truthvalue_conversion (expr);
  99       if (TREE_CODE (t) == ERROR_MARK)
 100         return t;
 101
 102       /* If it returns a NOP_EXPR, we must fold it here to avoid
 103          infinite recursion between fold () and convert ().  */
 104       if (TREE_CODE (t) == NOP_EXPR)
 105         return fold (build1 (NOP_EXPR, type, TREE_OPERAND (t, 0)));
 106       else
 107         return fold (build1 (NOP_EXPR, type, t));
 108     }
 109   if (code == POINTER_TYPE || code == REFERENCE_TYPE)
 110     return fold (convert_to_pointer (type, e));
 111   if (code == REAL_TYPE)
 112     return fold (convert_to_real (type, e));
 113   if (code == COMPLEX_TYPE)
 114     return fold (convert_to_complex (type, e));
 115   if (code == VECTOR_TYPE)
 116     return fold (convert_to_vector (type, e));
 117   if ((code == RECORD_TYPE || code == UNION_TYPE)
 118       && lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
 119       return e;
 120
 121   error ("conversion to non-scalar type requested");
 122   return error_mark_node;
 123 }