gdb/expression.h

   1 /* Definitions for expressions stored in reversed prefix form, for GDB.
   2    Copyright (C) 1986 Free Software Foundation, Inc.
   3
   4 GDB is distributed in the hope that it will be useful, but WITHOUT ANY
   5 WARRANTY.  No author or distributor accepts responsibility to anyone
   6 for the consequences of using it or for whether it serves any
   7 particular purpose or works at all, unless he says so in writing.
   8 Refer to the GDB General Public License for full details.
   9
  10 Everyone is granted permission to copy, modify and redistribute GDB,
  11 but only under the conditions described in the GDB General Public
  12 License.  A copy of this license is supposed to have been given to you
  13 along with GDB so you can know your rights and responsibilities.  It
  14 should be in a file named COPYING.  Among other things, the copyright
  15 notice and this notice must be preserved on all copies.
  16
  17 In other words, go ahead and share GDB, but don't try to stop
  18 anyone else from sharing it farther.  Help stamp out software hoarding!
  19 */
  20
  21 /* Definitions for saved C expressions.  */
  22
  23 /* An expression is represented as a vector of union exp_element's.
  24    Each exp_element is an opcode, except that some opcodes cause
  25    the following exp_element to be treated as a long or double constant
  26    or as a variable.  The opcodes are obeyed, using a stack for temporaries.
  27    The value is left on the temporary stack at the end.  */
  28
  29 /* When it is necessary to include a string,
  30    it can occupy as many exp_elements as it needs.
  31    We find the length of the string using strlen,
  32    divide to find out how many exp_elements are used up,
  33    and skip that many.  Strings, like numbers, are indicated
  34    by the preceding opcode.  */
  35
  36 enum exp_opcode
  37 {
  38 /* BINOP_... operate on two values computed by following subexpressions,
  39    replacing them by one result value.  They take no immediate arguments.  */
  40   BINOP_ADD,            /* + */
  41   BINOP_SUB,            /* - */
  42   BINOP_MUL,            /* * */
  43   BINOP_DIV,            /* / */
  44   BINOP_REM,            /* % */
  45   BINOP_LSH,            /* << */
  46   BINOP_RSH,            /* >> */
  47   BINOP_AND,            /* && */
  48   BINOP_OR,             /* || */
  49   BINOP_LOGAND,         /* & */
  50   BINOP_LOGIOR,         /* | */
  51   BINOP_LOGXOR,         /* ^ */
  52   BINOP_EQUAL,          /* == */
  53   BINOP_NOTEQUAL,       /* != */
  54   BINOP_LESS,           /* < */
  55   BINOP_GTR,            /* > */
  56   BINOP_LEQ,            /* <= */
  57   BINOP_GEQ,            /* >= */
  58   BINOP_REPEAT,         /* @ */
  59   BINOP_ASSIGN,         /* = */
  60   BINOP_COMMA,          /* , */
  61   BINOP_SUBSCRIPT,      /* x[y] */
  62   BINOP_EXP,            /* Exponentiation */
  63
  64 /* C++.  */
  65   BINOP_MIN,            /* <? */
  66   BINOP_MAX,            /* >? */
  67   BINOP_SCOPE,          /* :: */
  68
  69   /* STRUCTOP_MEMBER is used for pointer-to-member constructs.
  70      X . * Y translates into X STRUCTOP_MEMBER Y.  */
  71   STRUCTOP_MEMBER,
  72   /* STRUCTOP_MPTR is used for pointer-to-member constructs
  73      when X is a pointer instead of an aggregate.  */
  74   STRUCTOP_MPTR,
  75 /* end of C++.  */
  76
  77   BINOP_END,
  78
  79   BINOP_ASSIGN_MODIFY,  /* +=, -=, *=, and so on.
  80                            The following exp_element is another opcode,
  81                            a BINOP_, saying how to modify.
  82                            Then comes another BINOP_ASSIGN_MODIFY,
  83                            making three exp_elements in total.  */
  84
  85 /* Operates on three values computed by following subexpressions.  */
  86   TERNOP_COND,          /* ?: */
  87
  88 /* The OP_... series take immediate following arguments.
  89    After the arguments come another OP_... (the same one)
  90    so that the grouping can be recognized from the end.  */
  91
  92 /* OP_LONG is followed by a type pointer in the next exp_element
  93    and the long constant value in the following exp_element.
  94    Then comes another OP_LONG.
  95    Thus, the operation occupies four exp_elements.  */
  96
  97   OP_LONG,
  98 /* OP_DOUBLE is similar but takes a double constant instead of a long one.  */
  99   OP_DOUBLE,
 100 /* OP_VAR_VALUE takes one struct symbol * in the following exp_element,
 101    followed by another OP_VAR_VALUE, making three exp_elements.  */
 102   OP_VAR_VALUE,
 103 /* OP_LAST is followed by an integer in the next exp_element.
 104    The integer is zero for the last value printed,
 105    or it is the absolute number of a history element.
 106    With another OP_LAST at the end, this makes three exp_elements.  */
 107   OP_LAST,
 108 /* OP_REGISTER is followed by an integer in the next exp_element.
 109    This is the number of a register to fetch (as an int).
 110    With another OP_REGISTER at the end, this makes three exp_elements.  */
 111   OP_REGISTER,
 112 /* OP_INTERNALVAR is followed by an internalvar ptr in the next exp_element.
 113    With another OP_INTERNALVAR at the end, this makes three exp_elements.  */
 114   OP_INTERNALVAR,
 115 /* OP_FUNCALL is followed by an integer in the next exp_element.
 116    The integer is the number of args to the function call.
 117    That many plus one values from following subexpressions
 118    are used, the first one being the function.
 119    The integer is followed by a repeat of OP_FUNCALL,
 120    making three exp_elements.  */
 121   OP_FUNCALL,
 122 /* OP_STRING represents a string constant.
 123    Its format is the same as that of a STRUCTOP, but the string
 124    data is just made into a string constant when the operation
 125    is executed.  */
 126   OP_STRING,
 127
 128 /* UNOP_CAST is followed by a type pointer in the next exp_element.
 129    With another UNOP_CAST at the end, this makes three exp_elements.
 130    It casts the value of the following subexpression.  */
 131   UNOP_CAST,
 132 /* UNOP_MEMVAL is followed by a type pointer in the next exp_element
 133    With another UNOP_MEMVAL at the end, this makes three exp_elements.
 134    It casts the contents of the word addressed by the value of the
 135    following subexpression.  */
 136   UNOP_MEMVAL,
 137 /* UNOP_... operate on one value from a following subexpression
 138    and replace it with a result.  They take no immediate arguments.  */
 139   UNOP_NEG,             /* Unary - */
 140   UNOP_ZEROP,           /* Unary ! */
 141   UNOP_LOGNOT,          /* Unary ~ */
 142   UNOP_IND,             /* Unary * */
 143   UNOP_ADDR,            /* Unary & */
 144   UNOP_PREINCREMENT,    /* ++ before an expression */
 145   UNOP_POSTINCREMENT,   /* ++ after an expression */
 146   UNOP_PREDECREMENT,    /* -- before an expression */
 147   UNOP_POSTDECREMENT,   /* -- after an expression */
 148   UNOP_SIZEOF,          /* Unary sizeof (followed by expression) */
 149
 150 /* STRUCTOP_... operate on a value from a following subexpression
 151    by extracting a structure component specified by a string
 152    that appears in the following exp_elements (as many as needed).
 153    STRUCTOP_STRUCT is used for "." and STRUCTOP_PTR for "->".
 154    They differ only in the error message given in case the value is
 155    not suitable or the structure component specified is not found.
 156
 157    The length of the string follows in the next exp_element,
 158    (after the string), followed by another STRUCTOP_... code.  */
 159   STRUCTOP_STRUCT,
 160   STRUCTOP_PTR,
 161
 162 /* C++ */
 163   /* OP_THIS is just a placeholder for the class instance variable.
 164      It just comes in a tight (OP_THIS, OP_THIS) pair.  */
 165   OP_THIS,
 166
 167   /* OP_SCOPE surrounds a type name and a field name.  The type
 168      name is encoded as one element, but the field name stays as
 169      a string, which, of course, is variable length.  */
 170   OP_SCOPE,
 171
 172 };
 173
 174 union exp_element
 175 {
 176   enum exp_opcode opcode;
 177   struct symbol *symbol;
 178   long longconst;
 179   double doubleconst;
 180   char string;
 181   struct type *type;
 182   struct internalvar *internalvar;
 183 };
 184
 185 struct expression
 186 {
 187   int nelts;
 188   union exp_element elts[1];
 189 };
 190
 191 struct expression *parse_c_expression ();
 192 struct expression *parse_c_1 ();