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Annotation of GNUtools/cctools/as/expr.h, revision 1.1

1.1     ! root        1: /* expr.h -> header file for expr.c
        !             2:    Copyright (C) 1987 Free Software Foundation, Inc.
        !             3: 
        !             4: This file is part of GAS, the GNU Assembler.
        !             5: 
        !             6: GAS is free software; you can redistribute it and/or modify
        !             7: it under the terms of the GNU General Public License as published by
        !             8: the Free Software Foundation; either version 1, or (at your option)
        !             9: any later version.
        !            10: 
        !            11: GAS is distributed in the hope that it will be useful,
        !            12: but WITHOUT ANY WARRANTY; without even the implied warranty of
        !            13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
        !            14: GNU General Public License for more details.
        !            15: 
        !            16: You should have received a copy of the GNU General Public License
        !            17: along with GAS; see the file COPYING.  If not, write to
        !            18: the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
        !            19: 
        !            20: #import "struc-symbol.h"
        !            21: #import "bignum.h"
        !            22: #import "flonum.h"
        !            23: 
        !            24: /*
        !            25:  * This table describes the use of segments as EXPRESSION types.
        !            26:  *
        !            27:  *     X_seg   X_add_symbol  X_subtract_symbol X_add_number
        !            28:  * SEG_NONE                                            no (legal) expression
        !            29:  * SEG_BIG                                     *       > 32 bits const.
        !            30:  * SEG_ABSOLUTE                                        0
        !            31:  * SEG_SECT            *                       0
        !            32:  * SEG_UNKNOWN         *                       0
        !            33:  * SEG_DIFFSECT                0               *       0
        !            34:  *
        !            35:  * The blank fields MUST be 0, and are nugatory.
        !            36:  * The '0' fields MAY be 0. The '*' fields MAY NOT be 0.
        !            37:  *
        !            38:  * SEG_BIG: A floating point number or an integer larger than 32 bits.
        !            39:  *   For a floating point number:
        !            40:  *     X_add_number is < 0
        !            41:  *         The result is in the global variable generic_floating_point_number.
        !            42:  *         The value in X_add_number is -'c' where c is the character that
        !            43:  *         introduced the constant.  e.g. "0f6.9" will have  -'f' as a
        !            44:  *         X_add_number value.
        !            45:  *   For an integer larger than 32 bits:
        !            46:  *     X_add_number > 0
        !            47:  *         The result is in the global variable generic_bignum.
        !            48:  *         The value in X_add_number is a count of how many littlenums it
        !            49:  *         took to represent the bignum.
        !            50:  */
        !            51: typedef enum {
        !            52:     SEG_ABSOLUTE,      /* absolute */
        !            53:     SEG_SECT,          /* normal defined section */
        !            54:     SEG_DIFFSECT,      /* difference between symbols in sections */
        !            55:     SEG_UNKNOWN,       /* expression involving an undefined symbol */
        !            56:     SEG_NONE,          /* no expression */
        !            57:     SEG_BIG            /* bigger than 32 bits constant */
        !            58: } segT;
        !            59: 
        !            60: extern char *seg_name[];
        !            61: extern segT N_TYPE_seg[];
        !            62: 
        !            63: /*
        !            64:  * When an expression is SEG_BIG, it is in these globals (see comments above
        !            65:  * about SEG_BIG).  This data may be clobbered whenever expr() is called.
        !            66:  */
        !            67: extern FLONUM_TYPE    generic_floating_point_number;
        !            68: extern LITTLENUM_TYPE generic_bignum[];
        !            69: #define SIZE_OF_LARGE_NUMBER (20)      /* Number of littlenums in above */
        !            70:                                        /* generic_bignum which is enough to */
        !            71:                                        /* hold most precise flonum. */
        !            72: 
        !            73: /*
        !            74:  * Abbreviations (mnemonics).
        !            75:  *
        !            76:  *     O       operator
        !            77:  *     Q       quantity,  operand
        !            78:  *     X       eXpression
        !            79:  */
        !            80: 
        !            81: /*
        !            82:  * By popular demand, we define a struct to represent an expression.
        !            83:  * This will no doubt mutate as expressions become baroque.
        !            84:  *
        !            85:  * Currently, we support expressions like "foo-bar+42".
        !            86:  * In other words we permit a (possibly undefined) minuend, a
        !            87:  * (possibly undefined) subtrahend and an (absolute) augend.
        !            88:  * RMS says this is so we can have 1-pass assembly for any compiler
        !            89:  * emmissions, and a 'case' statement might emit 'undefined1 - undefined2'.
        !            90:  *
        !            91:  * To simplify table-driven dispatch, we also have a "segment" for the
        !            92:  * entire expression. That way we don't require complex reasoning about
        !            93:  * whether particular components are defined; and we can change component
        !            94:  * semantics without re-working all the dispatch tables in the assembler.
        !            95:  * In other words the "type" of an expression is its segment.
        !            96:  */
        !            97: 
        !            98: typedef struct {
        !            99:     symbolS *X_add_symbol;     /* foo */
        !           100:     symbolS *X_subtract_symbol;        /* bar */
        !           101:     long     X_add_number;     /* 42 (must be signed) */
        !           102:     segT     X_seg;            /* What segment (expr type) */
        !           103: } expressionS;
        !           104: 
        !           105: extern segT expression(
        !           106:     expressionS *resultP);
        !           107: extern char get_symbol_end(
        !           108:     void);
        !           109: extern segT try_to_make_absolute(
        !           110:     expressionS *expressionP);

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