gcc/c-convert.c

   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 \f
  52 /* Subroutines of `convert'.  */
  53
  54
  55 \f
  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 }