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 "c-tree.h"
  37 #include "langhooks.h"
  38 #include "toplev.h"
  39
  40 /* Change of width--truncation and extension of integers or reals--
  41    is represented with NOP_EXPR.  Proper functioning of many things
  42    assumes that no other conversions can be NOP_EXPRs.
  43
  44    Conversion between integer and pointer is represented with CONVERT_EXPR.
  45    Converting integer to real uses FLOAT_EXPR
  46    and real to integer uses FIX_TRUNC_EXPR.
  47
  48    Here is a list of all the functions that assume that widening and
  49    narrowing is always done with a NOP_EXPR:
  50      In convert.c, convert_to_integer.
  51      In c-typeck.c, build_binary_op (boolean ops), and
  52         c_common_truthvalue_conversion.
  53      In expr.c: expand_expr, for operands of a MULT_EXPR.
  54      In fold-const.c: fold.
  55      In tree.c: get_narrower and get_unwidened.  */
  56 \f
  57 /* Subroutines of `convert'.  */
  58
  59
  60 \f
  61 /* Create an expression whose value is that of EXPR,
  62    converted to type TYPE.  The TREE_TYPE of the value
  63    is always TYPE.  This function implements all reasonable
  64    conversions; callers should filter out those that are
  65    not permitted by the language being compiled.  */
  66
  67 tree
  68 convert (tree type, tree expr)
  69 {
  70   tree e = expr;
  71   enum tree_code code = TREE_CODE (type);
  72
  73   if (type == TREE_TYPE (expr)
  74       || TREE_CODE (expr) == ERROR_MARK
  75       || code == ERROR_MARK || TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
  76     return expr;
  77
  78   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)))
  79     return fold (build1 (NOP_EXPR, type, expr));
  80   if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
  81     return error_mark_node;
  82   if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
  83     {
  84       error ("void value not ignored as it ought to be");
  85       return error_mark_node;
  86     }
  87   if (code == VOID_TYPE)
  88     return build1 (CONVERT_EXPR, type, e);
  89 #if 0
  90   /* This is incorrect.  A truncation can't be stripped this way.
  91      Extensions will be stripped by the use of get_unwidened.  */
  92   if (TREE_CODE (expr) == NOP_EXPR)
  93     return convert (type, TREE_OPERAND (expr, 0));
  94 #endif
  95   if (code == INTEGER_TYPE || code == ENUMERAL_TYPE)
  96     return fold (convert_to_integer (type, e));
  97   if (code == BOOLEAN_TYPE)
  98     {
  99       tree t = c_objc_common_truthvalue_conversion (expr);
 100       if (TREE_CODE (t) == ERROR_MARK)
 101         return t;
 102
 103       /* If it returns a NOP_EXPR, we must fold it here to avoid
 104          infinite recursion between fold () and convert ().  */
 105       if (TREE_CODE (t) == NOP_EXPR)
 106         return fold (build1 (NOP_EXPR, type, TREE_OPERAND (t, 0)));
 107       else
 108         return fold (build1 (NOP_EXPR, type, t));
 109     }
 110   if (code == POINTER_TYPE || code == REFERENCE_TYPE)
 111     return fold (convert_to_pointer (type, e));
 112   if (code == REAL_TYPE)
 113     return fold (convert_to_real (type, e));
 114   if (code == COMPLEX_TYPE)
 115     return fold (convert_to_complex (type, e));
 116   if (code == VECTOR_TYPE)
 117     return fold (convert_to_vector (type, e));
 118   if ((code == RECORD_TYPE || code == UNION_TYPE)
 119       && lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
 120       return e;
 121
 122   error ("conversion to non-scalar type requested");
 123   return error_mark_node;
 124 }