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/*

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 *  matiec - a compiler for the programming languages defined in IEC 61131-3

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 *

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 *  Copyright (C) 2003-2011  Mario de Sousa (msousa@fe.up.pt)

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 *  Copyright (C) 2012       Manuele Conti (conti.ma@alice.it)

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 *

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 *  This program is free software: you can redistribute it and/or modify

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 *  it under the terms of the GNU General Public License as published by

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 *  the Free Software Foundation, either version 3 of the License, or

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 *  (at your option) any later version.

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 *

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 *  This program is distributed in the hope that it will be useful,

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 *  but WITHOUT ANY WARRANTY; without even the implied warranty of

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 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

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 *  GNU General Public License for more details.

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 *

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 *  You should have received a copy of the GNU General Public License

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 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.

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 *

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 *

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 * This code is made available on the understanding that it will not be

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 * used in safety-critical situations without a full and competent review.

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 */

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/*

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 * An IEC 61131-3 compiler.

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 *

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 * Based on the

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 * FINAL DRAFT - IEC 61131-3, 2nd Ed. (2001-12-10)

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 *

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 */

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/* Do constant folding...

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 *

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 * I.e., Determine the value of all expressions in which only constant values (i.e. literals) are used.

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 * The (constant) result of each operation is stored (annotated) in the respective operation symbol 

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 * (e.g.: add_expression_c) in the abstract syntax tree,

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 *

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 * For example:

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 *       2 + 3         -> the constant value '5'    is stored in the add_expression_c symbol.

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 *       22.2 - 5.0    -> the constant value '17.2' is stored in the add_expression_c symbol.

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 *       etc...

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 *

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 *

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 * NOTE 1 

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 *      Some operations and constants can have multiple data types. For example,

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 *        1 AND 0

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 *      may be either a BOOL, BYTE, WORD or LWORD.

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 *

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 *      The same happens with 

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 *        1 + 2

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 *      which may be signed (e.g. INT) or unsigned (UINT)

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 *

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 *      For the above reason, instead of storing a single constant value, we actually store 4:

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 *        - bool

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 *        - uint64

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 *        -  int64

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 *        - real64

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 *

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 *      Additionally, since the result of an operation may result in an overflow, we actually

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 *      store the result inside a struct (defined in absyntax.hh)

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 *

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 *             ** During stage 3 (semantic analysis/checking) we will be doing constant folding.

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 *              * That algorithm will anotate the abstract syntax tree with the result of operations

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 *              * on literals (i.e. 44 + 55 will store the result 99).

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 *              * Since the same source code (e.g. 1 + 0) may actually be a BOOL or an ANY_INT,

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 *              * or an ANY_BIT, we need to handle all possibilities, and determine the result of the

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 *              * operation assuming each type.

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 *              * For this reason, we have one entry for each possible type, with some expressions

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 *              * having more than one entry filled in!

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 *              **

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 *             typedef enum { cs_undefined,   // not defined --> const_value is not valid!

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 *                            cs_const_value, // const value is valid

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 *                            cs_overflow     // result produced overflow or underflow --> const_value is not valid!

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 *                          } const_status_t;

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 *    

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 *             typedef struct {

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 *                 const_status_t status;

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 *                 real64_t       value; 

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 *             } const_value_real64_t;

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 *             const_value_real64_t *const_value_real64; // when NULL --> UNDEFINED

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 *             

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 *             typedef struct {

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 *                 const_status_t status;

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 *                 int64_t        value; 

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 *             } const_value_int64_t;

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 *             const_value_int64_t *const_value_int64; // when NULL --> UNDEFINED

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 *             

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 *             typedef struct {

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 *                 const_status_t status;

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 *                 uint64_t       value; 

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 *             } const_value_uint64_t;

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 *             const_value_uint64_t *const_value_uint64; // when NULL --> UNDEFINED

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 *             

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 *             typedef struct {

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 *                 const_status_t status;

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 *                 bool           value; 

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 *             } const_value_bool_t;

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 *             const_value_bool_t *const_value_bool; // when NULL --> UNDEFINED

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 *

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 *

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 *

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 * NOTE 2 

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 *    This file does not print out any error messages!

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 *    We cannot really print out error messages when we find an overflow. Since each operation

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 *    (symbol in the absract syntax tree for that operation) will have up to 4 constant results,

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 *    it may happen that some of them overflow, while other do not.

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 *    We must wait for data type checking to determine the exact data type of each expression

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 *    before we can decide whether or not we should print out an overflow error message.

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 *

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 *    For this reason, this visitor merely annotates the abstract syntax tree, and leaves the

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 *    actuall printing of errors for the print_datatype_errors_c class!

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 */

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#include "constant_folding.hh"

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#include <limits>

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#include <math.h> /* required for pow function, and HUGE_VAL, HUGE_VALF, HUGE_VALL */

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#include <stdlib.h> /* required for malloc() */

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#define __STDC_LIMIT_MACROS /* required for UINT64_MAX, INT64_MAX, INT64_MIN, ... */

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#include <stdint.h>         /* required for UINT64_MAX, INT64_MAX, INT64_MIN, ... */

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#ifndef   UINT64_MAX 

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  #define UINT64_MAX (std::numeric_limits< uint64_t >::max())

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#endif

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#ifndef    INT64_MAX 

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  #define  INT64_MAX (std::numeric_limits<  int64_t >::max())

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#endif

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#ifndef    INT64_MIN

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  #define  INT64_MIN (std::numeric_limits<  int64_t >::min()) 

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#endif

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#if    (real64_t  == float)

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  #define HUGE_VAL64  HUGE_VALF

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#elif  (real64_t  == double)

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  #define HUGE_VAL64  HUGE_VAL

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#elif  (real64_t  == long_double)

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  #define HUGE_VAL64  HUGE_VALL

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#else 

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  #error Could not determine which data type is being used for real64_t (defined in absyntax.hh). Aborting!

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#endif

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#define FIRST_(symbol1, symbol2) (((symbol1)->first_order < (symbol2)->first_order)   ? (symbol1) : (symbol2))

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#define  LAST_(symbol1, symbol2) (((symbol1)->last_order  > (symbol2)->last_order)    ? (symbol1) : (symbol2))

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#define STAGE3_ERROR(error_level, symbol1, symbol2, ...) {                                                                  \

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  if (current_display_error_level >= error_level) {                                                                         \

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    fprintf(stderr, "%s:%d-%d..%d-%d: error: ",                                                                             \

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            FIRST_(symbol1,symbol2)->first_file, FIRST_(symbol1,symbol2)->first_line, FIRST_(symbol1,symbol2)->first_column,\

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                                                 LAST_(symbol1,symbol2) ->last_line,  LAST_(symbol1,symbol2) ->last_column);\

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    fprintf(stderr, __VA_ARGS__);                                                                                           \

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    fprintf(stderr, "\n");                                                                                                  \

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    error_count++;                                                                                                     \

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  }                                                                                                                         \

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}

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#define STAGE3_WARNING(symbol1, symbol2, ...) {                                                                             \

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    fprintf(stderr, "%s:%d-%d..%d-%d: warning: ",                                                                           \

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            FIRST_(symbol1,symbol2)->first_file, FIRST_(symbol1,symbol2)->first_line, FIRST_(symbol1,symbol2)->first_column,\

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                                                 LAST_(symbol1,symbol2) ->last_line,  LAST_(symbol1,symbol2) ->last_column);\

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    fprintf(stderr, __VA_ARGS__);                                                                                           \

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    fprintf(stderr, "\n");                                                                                                  \

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    warning_found = true;                                                                                                   \

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}

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#define NEW_CVALUE(dtype, symbol) \

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 (symbol->const_value_##dtype) = new(symbol_c::const_value_##dtype##_t); \

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 if ((symbol->const_value_##dtype) == NULL) ERROR; \

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 (symbol->const_value_##dtype)->status = symbol_c::cs_undefined;

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#define SET_CVALUE(dtype, symbol, new_value)  ((symbol)->const_value_##dtype->value) = new_value; ((symbol)->const_value_##dtype->status) = symbol_c::cs_const_value;  

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#define GET_CVALUE(dtype, symbol)             ((symbol)->const_value_##dtype->value) 

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#define SET_OVFLOW(dtype, symbol)             ((symbol)->const_value_##dtype->status) = symbol_c::cs_overflow

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    /* The following test is correct in the presence of a NULL pointer, as the logical evaluation will be suspended as soon as the first condition is false! */

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#define VALID_CVALUE(dtype, symbol)           ((NULL != (symbol)->const_value_##dtype) && (symbol_c::cs_const_value == (symbol)->const_value_##dtype->status))

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#define ISZERO_CVALUE(dtype, symbol)          ((VALID_CVALUE(dtype, symbol)) && (GET_CVALUE(dtype, symbol) == 0))

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#define DO_BINARY_OPER(dtype, oper, otype)\

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	if (VALID_CVALUE(dtype, symbol->r_exp) && VALID_CVALUE(dtype, symbol->l_exp)) {                                \

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		NEW_CVALUE(otype, symbol);                                                                             \

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		SET_CVALUE(otype, symbol, GET_CVALUE(dtype, symbol->l_exp) oper GET_CVALUE(dtype, symbol->r_exp));     \

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	}

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#define DO_UNARY_OPER(dtype, oper, arg)\

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	if (VALID_CVALUE(dtype, arg)) {                                                                                \

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		NEW_CVALUE(dtype, symbol);                                                                             \

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		SET_CVALUE(dtype, symbol, oper GET_CVALUE(dtype, arg));                                                \

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	}

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/* NOTE:

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 *   Most of the conditions to detect overflows on signed and unsigned integer operations were adapted from

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 *   https://www.securecoding.cert.org/confluence/display/seccode/INT32-C.+Ensure+that+operations+on+signed+integers+do+not+result+in+overflow?showComments=false

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 *   https://www.securecoding.cert.org/confluence/display/seccode/INT30-C.+Ensure+that+unsigned+integer+operations+do+not+wrap

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 */

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/* NOTE: If at all possible, all overflow tests are done by pre-condition tests, i.e. tests that 

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 *       can be run _before_ the operation is executed, and therefore without accessing the result!

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 *

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 *       The exception is for real/floating point values, that simply test if the result is NaN (not a number).

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 */

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/* res = a + b */

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static void CHECK_OVERFLOW_uint64_SUM(symbol_c *res, symbol_c *a, symbol_c *b) {

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	if (!VALID_CVALUE(uint64, res))

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		return;

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	/* Test by post-condition: If sum is smaller than either operand => overflow! */

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	// if (GET_CVALUE(uint64, res) < GET_CVALUE(uint64, a))

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	/* Test by pre-condition: If (UINT64_MAX - a) < b => overflow! */

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	if ((UINT64_MAX - GET_CVALUE(uint64, a)) < GET_CVALUE(uint64, b))

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		SET_OVFLOW(uint64, res);

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}

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/* res = a - b */

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static void CHECK_OVERFLOW_uint64_SUB(symbol_c *res, symbol_c *a, symbol_c *b) {

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	if (!VALID_CVALUE(uint64, res))

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		return;

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	/* Test by post-condition: If diference is larger than a => overflow! */

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	// if (GET_CVALUE(uint64, res) > GET_CVALUE(uint64, a))

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	/* Test by pre-condition: if b > a => overflow! */

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	if (GET_CVALUE(uint64, b) > GET_CVALUE(uint64, a))

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		SET_OVFLOW(uint64, res);

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}

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/* res = a * b */

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static void CHECK_OVERFLOW_uint64_MUL(symbol_c *res, symbol_c *a, symbol_c *b) {

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	if (!VALID_CVALUE(uint64, res))

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		return;

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	/* Test by pre-condition: If (UINT64_MAX / a) < b => overflow! */

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	if ((UINT64_MAX / GET_CVALUE(uint64, a)) < GET_CVALUE(uint64, b))

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		SET_OVFLOW(uint64, res);

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}

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/* res = a / b */

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static void CHECK_OVERFLOW_uint64_DIV(symbol_c *res, symbol_c *a, symbol_c *b) {

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	if (!VALID_CVALUE(uint64, res))

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		return;

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	if (GET_CVALUE(uint64, b) == 0) /* division by zero! */

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		SET_OVFLOW(uint64, res);

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}

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/* res = a MOD b */

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static void CHECK_OVERFLOW_uint64_MOD(symbol_c *res, symbol_c *a, symbol_c *b) {

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	if (!VALID_CVALUE(uint64, res))

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		return;

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	/* no overflow condition exists, including division by zero, which IEC 61131-3 considers legal for MOD operation! */

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	if (false) 

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		SET_OVFLOW(uint64, res);

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}

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/* res = a + b */

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static void CHECK_OVERFLOW_int64_SUM(symbol_c *res, symbol_c *a_ptr, symbol_c *b_ptr) {

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	if (!VALID_CVALUE(int64, res))

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		return;

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	int64_t a = GET_CVALUE(int64, a_ptr);

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	int64_t b = GET_CVALUE(int64, b_ptr);

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	/* The following test is valid no matter what representation is being used (e.g. two's complement, etc...) */

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	if (((b > 0) && (a > (INT64_MAX - b)))

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	 || ((b < 0) && (a < (INT64_MIN - b))))

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		SET_OVFLOW(int64, res);

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}

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/* res = a - b */

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static void CHECK_OVERFLOW_int64_SUB(symbol_c *res, symbol_c *a_ptr, symbol_c *b_ptr) {

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	if (!VALID_CVALUE(int64, res))

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		return;

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	int64_t a = GET_CVALUE(int64, a_ptr);

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	int64_t b = GET_CVALUE(int64, b_ptr);

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	/* The following test is valid no matter what representation is being used (e.g. two's complement, etc...) */

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	if (((b > 0) && (a < (INT64_MIN + b)))

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	 || ((b < 0) && (a > (INT64_MAX + b))))

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		SET_OVFLOW(int64, res);

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}

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/* res = a * b */

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static void CHECK_OVERFLOW_int64_MUL(symbol_c *res, symbol_c *a_ptr, symbol_c *b_ptr) {

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	if (!VALID_CVALUE(int64, res))

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		return;

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	int64_t a = GET_CVALUE(int64, a_ptr);

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	int64_t b = GET_CVALUE(int64, b_ptr);

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	if (   ( (a > 0) &&  (b > 0) &&             (a > (INT64_MAX / b))) 

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	    || ( (a > 0) && !(b > 0) &&             (b < (INT64_MIN / a))) 

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	    || (!(a > 0) &&  (b > 0) &&             (a < (INT64_MIN / b))) 

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	    || (!(a > 0) && !(b > 0) && (a != 0) && (b < (INT64_MAX / a))))

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		SET_OVFLOW(int64, res);

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}

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/* res = a / b */

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static void CHECK_OVERFLOW_int64_DIV(symbol_c *res, symbol_c *a_ptr, symbol_c *b_ptr) {

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	if (!VALID_CVALUE(int64, res))

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		return;

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	int64_t a = GET_CVALUE(int64, a_ptr);

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	int64_t b = GET_CVALUE(int64, b_ptr);

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	if ((b == 0) || ((a == INT64_MIN) && (b == -1)))

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		SET_OVFLOW(int64, res);

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}

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/* res = a MOD b */

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static void CHECK_OVERFLOW_int64_MOD(symbol_c *res, symbol_c *a_ptr, symbol_c *b_ptr) {

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	if (!VALID_CVALUE(int64, res))

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		return;

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	int64_t a = GET_CVALUE(int64, a_ptr);