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Guard against single operand multiplication when detecting like terms This *shouldn't* happen, but it apparently does in some pathological cases so guard against a single operand multiplication to prevent a crash.
author William Astle <lost@l-w.ca>
date Mon, 04 Nov 2024 23:48:23 -0700
parents 2c24602be78f
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1 /*
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2 expr.h
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3 Copyright © 2009 William Astle
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4
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5 This file is part of LWLINK.
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6
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7 LWLINK is free software: you can redistribute it and/or modify it under the
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8 terms of the GNU General Public License as published by the Free Software
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9 Foundation, either version 3 of the License, or (at your option) any later
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10 version.
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11
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12 This program is distributed in the hope that it will be useful, but WITHOUT
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13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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15 more details.
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16
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17 You should have received a copy of the GNU General Public License along with
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18 this program. If not, see <http://www.gnu.org/licenses/>.
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19 */
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20
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21 /*
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22 Definitions for expression evaluator
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23 */
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24
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25 #ifndef __expr_h_seen__
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26 #define __expr_h_seen__
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27
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28 #ifndef __expr_c_seen__
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29 #define __expr_E__ extern
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30 #else
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31 #define __expr_E__
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32 #endif
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33
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34 // term types
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35 #define LW_TERM_NONE 0
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36 #define LW_TERM_OPER 1 // an operator
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37 #define LW_TERM_INT 2 // 32 bit signed integer
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38 #define LW_TERM_SYM 3 // symbol reference
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39
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40 // operator types
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41 #define LW_OPER_NONE 0
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42 #define LW_OPER_PLUS 1 // +
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43 #define LW_OPER_MINUS 2 // -
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44 #define LW_OPER_TIMES 3 // *
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45 #define LW_OPER_DIVIDE 4 // /
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46 #define LW_OPER_MOD 5 // %
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47 #define LW_OPER_INTDIV 6 // \ (don't end line with \)
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48 #define LW_OPER_BWAND 7 // bitwise AND
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49 #define LW_OPER_BWOR 8 // bitwise OR
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50 #define LW_OPER_BWXOR 9 // bitwise XOR
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51 #define LW_OPER_AND 10 // boolean AND
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52 #define LW_OPER_OR 11 // boolean OR
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53 #define LW_OPER_NEG 12 // - unary negation (2's complement)
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54 #define LW_OPER_COM 13 // ^ unary 1's complement
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55
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56
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57 // term structure
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58 typedef struct lw_expr_term_s
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59 {
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60 int term_type; // type of term (see above)
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61 char *symbol; // name of a symbol
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62 int value; // value of the term (int) or operator number (OPER)
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63 } lw_expr_term_t;
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64
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65 // type for an expression evaluation stack
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66 typedef struct lw_expr_stack_node_s lw_expr_stack_node_t;
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67 struct lw_expr_stack_node_s
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68 {
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69 lw_expr_term_t *term;
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70 lw_expr_stack_node_t *prev;
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71 lw_expr_stack_node_t *next;
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72 };
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73
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74 typedef struct lw_expr_stack_s
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75 {
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76 lw_expr_stack_node_t *head;
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77 lw_expr_stack_node_t *tail;
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78 } lw_expr_stack_t;
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79
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80 __expr_E__ void lw_expr_term_free(lw_expr_term_t *t);
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81 __expr_E__ lw_expr_term_t *lw_expr_term_create_oper(int oper);
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82 __expr_E__ lw_expr_term_t *lw_expr_term_create_sym(char *sym, int symtype);
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83 __expr_E__ lw_expr_term_t *lw_expr_term_create_int(int val);
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84 __expr_E__ lw_expr_term_t *lw_expr_term_dup(lw_expr_term_t *t);
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85
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86 __expr_E__ void lw_expr_stack_free(lw_expr_stack_t *s);
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87 __expr_E__ lw_expr_stack_t *lw_expr_stack_create(void);
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88 __expr_E__ lw_expr_stack_t *lw_expr_stack_dup(lw_expr_stack_t *s);
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89
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90 __expr_E__ void lw_expr_stack_push(lw_expr_stack_t *s, lw_expr_term_t *t);
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91 __expr_E__ lw_expr_term_t *lw_expr_stack_pop(lw_expr_stack_t *s);
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92
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93 // simplify expression
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94 __expr_E__ int lw_expr_reval(lw_expr_stack_t *s, lw_expr_stack_t *(*sfunc)(char *sym, int symtype, void *state), void *state);
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95
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96 // useful macros
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97 // is the expression "simple" (one term)?
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98 #define lw_expr_is_simple(s) ((s) -> head == (s) -> tail)
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99
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100 // is the expression constant?
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101 #define lw_expr_is_constant(s) (lw_expr_is_simple(s) && (!((s) -> head) || (s) -> head -> term -> term_type == LW_TERM_INT))
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102
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103 // get the constant value of an expression or 0 if not constant
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104 #define lw_expr_get_value(s) (lw_expr_is_constant(s) ? ((s) -> head ? (s) -> head -> term -> value : 0) : 0)
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105
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106 #undef __expr_E__
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107
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108 #endif // __expr_h_seen__