zerobyte.asm: use a real instruction to avoid confusing ndisasm

[nasm.git] / nasm.h

/* nasm.h   main header file for the Netwide Assembler: inter-module interface
 *
 * The Netwide Assembler is copyright (C) 1996 Simon Tatham and
 * Julian Hall. All rights reserved. The software is
 * redistributable under the licence given in the file "Licence"
 * distributed in the NASM archive.
 *
 * initial version: 27/iii/95 by Simon Tatham
 */

#ifndef NASM_NASM_H
#define NASM_NASM_H

#include "compiler.h"

#include <stdio.h>
#include <inttypes.h>
#include "version.h"            /* generated NASM version macros */
#include "nasmlib.h"
#include "insnsi.h"             /* For enum opcode */

#ifndef NULL
#define NULL 0
#endif

#ifndef FALSE
#define FALSE 0                 /* comes in handy */
#endif
#ifndef TRUE
#define TRUE 1
#endif

#define NO_SEG -1L              /* null segment value */
#define SEG_ABS 0x40000000L     /* mask for far-absolute segments */

#ifndef FILENAME_MAX
#define FILENAME_MAX 256
#endif

#ifndef PREFIX_MAX
#define PREFIX_MAX 10
#endif

#ifndef POSTFIX_MAX
#define POSTFIX_MAX 10
#endif

#define IDLEN_MAX 4096

/*
 * Name pollution problems: <time.h> on Digital UNIX pulls in some
 * strange hardware header file which sees fit to define R_SP. We
 * undefine it here so as not to break the enum below.
 */
#ifdef R_SP
#undef R_SP
#endif

/*
 * We must declare the existence of this structure type up here,
 * since we have to reference it before we define it...
 */
struct ofmt;

/*
 * -----------------------
 * Other function typedefs
 * -----------------------
 */

/*
 * A label-lookup function should look like this.
 */
typedef int (*lfunc) (char *label, int32_t *segment, int32_t *offset);

/*
 * And a label-definition function like this. The boolean parameter
 * `is_norm' states whether the label is a `normal' label (which
 * should affect the local-label system), or something odder like
 * an EQU or a segment-base symbol, which shouldn't.
 */
typedef void (*ldfunc) (char *label, int32_t segment, int32_t offset,
                        char *special, int is_norm, int isextrn,
                        struct ofmt * ofmt, efunc error);

/*
 * List-file generators should look like this:
 */
typedef struct {
    /*
     * Called to initialize the listing file generator. Before this
     * is called, the other routines will silently do nothing when
     * called. The `char *' parameter is the file name to write the
     * listing to.
     */
    void (*init) (char *, efunc);

    /*
     * Called to clear stuff up and close the listing file.
     */
    void (*cleanup) (void);

    /*
     * Called to output binary data. Parameters are: the offset;
     * the data; the data type. Data types are similar to the
     * output-format interface, only OUT_ADDRESS will _always_ be
     * displayed as if it's relocatable, so ensure that any non-
     * relocatable address has been converted to OUT_RAWDATA by
     * then. Note that OUT_RAWDATA+0 is a valid data type, and is a
     * dummy call used to give the listing generator an offset to
     * work with when doing things like uplevel(LIST_TIMES) or
     * uplevel(LIST_INCBIN).
     */
    void (*output) (int32_t, const void *, uint32_t);

    /*
     * Called to send a text line to the listing generator. The
     * `int' parameter is LIST_READ or LIST_MACRO depending on
     * whether the line came directly from an input file or is the
     * result of a multi-line macro expansion.
     */
    void (*line) (int, char *);

    /*
     * Called to change one of the various levelled mechanisms in
     * the listing generator. LIST_INCLUDE and LIST_MACRO can be
     * used to increase the nesting level of include files and
     * macro expansions; LIST_TIMES and LIST_INCBIN switch on the
     * two binary-output-suppression mechanisms for large-scale
     * pseudo-instructions.
     *
     * LIST_MACRO_NOLIST is synonymous with LIST_MACRO except that
     * it indicates the beginning of the expansion of a `nolist'
     * macro, so anything under that level won't be expanded unless
     * it includes another file.
     */
    void (*uplevel) (int);

    /*
     * Reverse the effects of uplevel.
     */
    void (*downlevel) (int);
} ListGen;

/*
 * The expression evaluator must be passed a scanner function; a
 * standard scanner is provided as part of nasmlib.c. The
 * preprocessor will use a different one. Scanners, and the
 * token-value structures they return, look like this.
 *
 * The return value from the scanner is always a copy of the
 * `t_type' field in the structure.
 */
struct tokenval {
    int t_type;
    int64_t t_integer, t_inttwo;
    char *t_charptr;
};
typedef int (*scanner) (void *private_data, struct tokenval * tv);

/*
 * Token types returned by the scanner, in addition to ordinary
 * ASCII character values, and zero for end-of-string.
 */
enum {                          /* token types, other than chars */
    TOKEN_INVALID = -1,         /* a placeholder value */
    TOKEN_EOS = 0,              /* end of string */
    TOKEN_EQ = '=', TOKEN_GT = '>', TOKEN_LT = '<',     /* aliases */
    TOKEN_ID = 256, TOKEN_NUM, TOKEN_REG, TOKEN_INSN,   /* major token types */
    TOKEN_ERRNUM,               /* numeric constant with error in */
    TOKEN_HERE, TOKEN_BASE,     /* $ and $$ */
    TOKEN_SPECIAL,              /* BYTE, WORD, DWORD, QWORD, FAR, NEAR, etc */
    TOKEN_PREFIX,               /* A32, O16, LOCK, REPNZ, TIMES, etc */
    TOKEN_SHL, TOKEN_SHR,       /* << and >> */
    TOKEN_SDIV, TOKEN_SMOD,     /* // and %% */
    TOKEN_GE, TOKEN_LE, TOKEN_NE,       /* >=, <= and <> (!= is same as <>) */
    TOKEN_DBL_AND, TOKEN_DBL_OR, TOKEN_DBL_XOR, /* &&, || and ^^ */
    TOKEN_SEG, TOKEN_WRT,       /* SEG and WRT */
    TOKEN_FLOAT,                /* floating-point constant */
    TOKEN_FLOATIZE,             /* __floatX__ */
};

enum floatize {
    FLOAT_16,
    FLOAT_32,
    FLOAT_64,
    FLOAT_80M,
    FLOAT_80E,
    FLOAT_128L,
    FLOAT_128H,
};

struct location {
    int64_t offset;
    int32_t segment;
    int known;
};

/*
 * Expression-evaluator datatype. Expressions, within the
 * evaluator, are stored as an array of these beasts, terminated by
 * a record with type==0. Mostly, it's a vector type: each type
 * denotes some kind of a component, and the value denotes the
 * multiple of that component present in the expression. The
 * exception is the WRT type, whose `value' field denotes the
 * segment to which the expression is relative. These segments will
 * be segment-base types, i.e. either odd segment values or SEG_ABS
 * types. So it is still valid to assume that anything with a
 * `value' field of zero is insignificant.
 */
typedef struct {
    int32_t type;                  /* a register, or EXPR_xxx */
    int64_t value;                 /* must be >= 32 bits */
} expr;

/*
 * Library routines to manipulate expression data types.
 */
int is_reloc(expr *);
int is_simple(expr *);
int is_really_simple(expr *);
int is_unknown(expr *);
int is_just_unknown(expr *);
int64_t reloc_value(expr *);
int32_t reloc_seg(expr *);
int32_t reloc_wrt(expr *);

/*
 * The evaluator can also return hints about which of two registers
 * used in an expression should be the base register. See also the
 * `operand' structure.
 */
struct eval_hints {
    int64_t base;
    int type;
};

/*
 * The actual expression evaluator function looks like this. When
 * called, it expects the first token of its expression to already
 * be in `*tv'; if it is not, set tv->t_type to TOKEN_INVALID and
 * it will start by calling the scanner.
 *
 * If a forward reference happens during evaluation, the evaluator
 * must set `*fwref' to TRUE if `fwref' is non-NULL.
 *
 * `critical' is non-zero if the expression may not contain forward
 * references. The evaluator will report its own error if this
 * occurs; if `critical' is 1, the error will be "symbol not
 * defined before use", whereas if `critical' is 2, the error will
 * be "symbol undefined".
 *
 * If `critical' has bit 8 set (in addition to its main value: 0x101
 * and 0x102 correspond to 1 and 2) then an extended expression
 * syntax is recognised, in which relational operators such as =, <
 * and >= are accepted, as well as low-precedence logical operators
 * &&, ^^ and ||.
 *
 * If `hints' is non-NULL, it gets filled in with some hints as to
 * the base register in complex effective addresses.
 */
#define CRITICAL 0x100
typedef expr *(*evalfunc) (scanner sc, void *scprivate,
                           struct tokenval * tv, int *fwref, int critical,
                           efunc error, struct eval_hints * hints);

/*
 * Special values for expr->type.  These come after EXPR_REG_END
 * as defined in regs.h.
 */

#define EXPR_UNKNOWN    (EXPR_REG_END+1) /* forward references */
#define EXPR_SIMPLE     (EXPR_REG_END+2)
#define EXPR_WRT        (EXPR_REG_END+3)
#define EXPR_SEGBASE    (EXPR_REG_END+4)

/*
 * Preprocessors ought to look like this:
 */
typedef struct preproc_ops {
    /*
     * Called at the start of a pass; given a file name, the number
     * of the pass, an error reporting function, an evaluator
     * function, and a listing generator to talk to.
     */
    void (*reset) (char *, int, efunc, evalfunc, ListGen *);

    /*
     * Called to fetch a line of preprocessed source. The line
     * returned has been malloc'ed, and so should be freed after
     * use.
     */
    char *(*getline) (void);

    /*
     * Called at the end of a pass.
     */
    void (*cleanup) (int);
} Preproc;

extern Preproc nasmpp;

/*
 * ----------------------------------------------------------------
 * Some lexical properties of the NASM source language, included
 * here because they are shared between the parser and preprocessor
 * ----------------------------------------------------------------
 */

/*
 * isidstart matches any character that may start an identifier, and isidchar
 * matches any character that may appear at places other than the start of an
 * identifier. E.g. a period may only appear at the start of an identifier
 * (for local labels), whereas a number may appear anywhere *but* at the
 * start. 
 */

#define isidstart(c) ( isalpha(c) || (c)=='_' || (c)=='.' || (c)=='?' \
                                  || (c)=='@' )
#define isidchar(c)  ( isidstart(c) || isdigit(c) || (c)=='$' || (c)=='#' \
                                                  || (c)=='~' )

/* Ditto for numeric constants. */

#define isnumstart(c)  ( isdigit(c) || (c)=='$' )
#define isnumchar(c)   ( isalnum(c) )

/* This returns the numeric value of a given 'digit'. */

#define numvalue(c)  ((c)>='a' ? (c)-'a'+10 : (c)>='A' ? (c)-'A'+10 : (c)-'0')

/*
 * Data-type flags that get passed to listing-file routines.
 */
enum {
    LIST_READ, LIST_MACRO, LIST_MACRO_NOLIST, LIST_INCLUDE,
    LIST_INCBIN, LIST_TIMES
};

/*
 * -----------------------------------------------------------
 * Format of the `insn' structure returned from `parser.c' and
 * passed into `assemble.c'
 * -----------------------------------------------------------
 */

/*
 * Here we define the operand types. These are implemented as bit
 * masks, since some are subsets of others; e.g. AX in a MOV
 * instruction is a special operand type, whereas AX in other
 * contexts is just another 16-bit register. (Also, consider CL in
 * shift instructions, DX in OUT, etc.)
 *
 * The basic concept here is that
 *    (class & ~operand) == 0
 *
 * if and only if "operand" belongs to class type "class".
 *
 * The bits are assigned as follows:
 *
 * Bits 0-7, 29: sizes
 *  0:  8 bits (BYTE)
 *  1: 16 bits (WORD)
 *  2: 32 bits (DWORD)
 *  3: 64 bits (QWORD)
 *  4: 80 bits (TWORD)
 *  5: FAR
 *  6: NEAR
 *  7: SHORT
 * 29: 128 bits (OWORD)
 *
 * Bits 8-11 modifiers
 *  8: TO
 *  9: COLON
 * 10: STRICT
 * 11: (reserved)
 *
 * Bits 12-15: type of operand
 * 12: REGISTER
 * 13: IMMEDIATE
 * 14: MEMORY (always has REGMEM attribute as well)
 * 15: REGMEM (valid EA operand)
 *
 * Bits 16-19: subclasses
 * With REG_CDT:
 * 16: REG_CREG (CRx)
 * 17: REG_DREG (DRx)
 * 18: REG_TREG (TRx)

 * With REG_GPR:
 * 16: REG_ACCUM (AL, AX, EAX, RAX)
 * 17: REG_COUNT (CL, CX, ECX, RCX)
 * 18: REG_DATA  (DL, DX, EDX, RDX)
 * 19: REG_HIGH  (AH, CH, DH, BH)
 *
 * With REG_SREG:
 * 16: REG_CS
 * 17: REG_DESS (DS, ES, SS)
 * 18: REG_FSGS
 * 19: REG_SEG67
 *
 * With FPUREG:
 * 16: FPU0
 *
 * With XMMREG:
 * 16: XMM0
 *
 * With MEMORY:
 * 16: MEM_OFFS (this is a simple offset)
 * 17: IP_REL (IP-relative offset)
 *
 * With IMMEDIATE:
 * 16: UNITY (1)
 * 17: BYTENESS (-128..127)
 *
 * Bits 20-26: register classes
 * 20: REG_CDT (CRx, DRx, TRx)
 * 21: RM_GPR (REG_GPR) (integer register)
 * 22: REG_SREG
 * 23: IP_REG (RIP or EIP) [unused]
 * 24: FPUREG
 * 25: RM_MMX (MMXREG)
 * 26: RM_XMM (XMMREG)
 *
 * Bits 27-29 & 31 are currently unallocated.
 *
 * 30: SAME_AS
 * Special flag only used in instruction patterns; means this operand
 * has to be identical to another operand.  Currently only supported
 * for registers.
 */

typedef uint32_t opflags_t;

/* Size, and other attributes, of the operand */
#define BITS8           0x00000001L
#define BITS16          0x00000002L
#define BITS32          0x00000004L
#define BITS64          0x00000008L   /* x64 and FPU only */
#define BITS80          0x00000010L   /* FPU only */
#define BITS128         0x20000000L
#define FAR             0x00000020L   /* grotty: this means 16:16 or */
                                       /* 16:32, like in CALL/JMP */
#define NEAR            0x00000040L
#define SHORT           0x00000080L   /* and this means what it says :) */

#define SIZE_MASK       0x200000FFL   /* all the size attributes */

/* Modifiers */
#define MODIFIER_MASK   0x00000f00L
#define TO              0x00000100L   /* reverse effect in FADD, FSUB &c */
#define COLON           0x00000200L   /* operand is followed by a colon */
#define STRICT          0x00000400L   /* do not optimize this operand */

/* Type of operand: memory reference, register, etc. */
#define OPTYPE_MASK     0x0000f000L
#define REGISTER        0x00001000L   /* register number in 'basereg' */
#define IMMEDIATE       0x00002000L
#define MEMORY          0x0000c000L
#define REGMEM          0x00008000L   /* for r/m, ie EA, operands */

/* Register classes */
#define REG_EA          0x00009000L   /* 'normal' reg, qualifies as EA */
#define RM_GPR          0x00208000L   /* integer operand */
#define REG_GPR         0x00209000L   /* integer register */
#define REG8            0x00209001L   /*  8-bit GPR  */
#define REG16           0x00209002L   /* 16-bit GPR */
#define REG32           0x00209004L   /* 32-bit GPR */
#define REG64           0x00209008L   /* 64-bit GPR */
#define IP_REG          0x00801000L   /* RIP or EIP register */
#define RIPREG          0x00801008L   /* RIP */
#define EIPREG          0x00801004L   /* EIP */
#define FPUREG          0x01001000L   /* floating point stack registers */
#define FPU0            0x01011000L   /* FPU stack register zero */
#define RM_MMX          0x02008000L   /* MMX operand */
#define MMXREG          0x02009000L   /* MMX register */
#define RM_XMM          0x04008000L   /* XMM (SSE) operand */
#define XMMREG          0x04009000L   /* XMM (SSE) register */
#define XMM0            0x04019000L   /* XMM register zero */
#define REG_CDT         0x00101004L   /* CRn, DRn and TRn */
#define REG_CREG        0x00111004L   /* CRn */
#define REG_DREG        0x00121004L   /* DRn */
#define REG_TREG        0x00141004L   /* TRn */
#define REG_SREG        0x00401002L   /* any segment register */
#define REG_CS          0x00411002L   /* CS */
#define REG_DESS        0x00421002L   /* DS, ES, SS */
#define REG_FSGS        0x00441002L   /* FS, GS */
#define REG_SEG67       0x00481002L   /* Unimplemented segment registers */

#define REG_RIP         0x00801008L   /* RIP relative addressing */
#define REG_EIP         0x00801004L   /* EIP relative addressing */

/* Special GPRs */
#define REG_SMASK       0x000f0000L   /* a mask for the following */
#define REG_ACCUM       0x00219000L   /* accumulator: AL, AX, EAX, RAX */
#define REG_AL          0x00219001L
#define REG_AX          0x00219002L
#define REG_EAX         0x00219004L
#define REG_RAX         0x00219008L
#define REG_COUNT       0x00229000L   /* counter: CL, CX, ECX, RCX */
#define REG_CL          0x00229001L
#define REG_CX          0x00229002L
#define REG_ECX         0x00229004L
#define REG_RCX         0x00229008L
#define REG_DL          0x00249001L   /* data: DL, DX, EDX, RDX */
#define REG_DX          0x00249002L
#define REG_EDX         0x00249004L
#define REG_RDX         0x00249008L
#define REG_HIGH        0x00289001L   /* high regs: AH, CH, DH, BH */

/* special types of EAs */
#define MEM_OFFS        0x0001c000L   /* simple [address] offset - absolute! */
#define IP_REL          0x0002c000L   /* IP-relative offset */

/* memory which matches any type of r/m operand */
#define MEMORY_ANY      (MEMORY|RM_GPR|RM_MMX|RM_XMM)

/* special type of immediate operand */
#define UNITY           0x00012000L   /* for shift/rotate instructions */
#define SBYTE           0x00022000L   /* for op r16/32,immediate instrs. */

/* special flags */
#define SAME_AS         0x40000000L

/* Register names automatically generated from regs.dat */
#include "regs.h"

enum ccode {                    /* condition code names */
    C_A, C_AE, C_B, C_BE, C_C, C_E, C_G, C_GE, C_L, C_LE, C_NA, C_NAE,
    C_NB, C_NBE, C_NC, C_NE, C_NG, C_NGE, C_NL, C_NLE, C_NO, C_NP,
    C_NS, C_NZ, C_O, C_P, C_PE, C_PO, C_S, C_Z,
    C_none = -1
};

/*
 * REX flags
 */
#define REX_OC          0x0200  /* DREX suffix has the OC0 bit set */
#define REX_D           0x0100  /* Instruction uses DREX instead of REX */
#define REX_H           0x80    /* High register present, REX forbidden */
#define REX_P           0x40    /* REX prefix present/required */
#define REX_L           0x20    /* Use LOCK prefix instead of REX.R */
#define REX_W           0x08    /* 64-bit operand size */
#define REX_R           0x04    /* ModRM reg extension */
#define REX_X           0x02    /* SIB index extension */
#define REX_B           0x01    /* ModRM r/m extension */
#define REX_REAL        0x4f    /* Actual REX prefix bits */

/*
 * Note that because segment registers may be used as instruction
 * prefixes, we must ensure the enumerations for prefixes and
 * register names do not overlap.
 */
enum prefixes {                 /* instruction prefixes */
    PREFIX_ENUM_START = REG_ENUM_LIMIT,
    P_A16 = PREFIX_ENUM_START, P_A32, P_LOCK, P_O16, P_O32,
    P_REP, P_REPE, P_REPNE, P_REPNZ, P_REPZ, P_TIMES
};

enum {                          /* extended operand types */
    EOT_NOTHING, EOT_DB_STRING, EOT_DB_NUMBER
};

enum {                          /* special EA flags */
    EAF_BYTEOFFS =  1,          /* force offset part to byte size */
    EAF_WORDOFFS =  2,          /* force offset part to [d]word size */
    EAF_TIMESTWO =  4,          /* really do EAX*2 not EAX+EAX */
    EAF_REL      =  8,          /* IP-relative addressing */
    EAF_ABS      = 16,          /* non-IP-relative addressing */
    EAF_FSGS     = 32           /* fs/gs segment override present */
};

enum eval_hint {                /* values for `hinttype' */
    EAH_NOHINT   = 0,           /* no hint at all - our discretion */
    EAH_MAKEBASE = 1,           /* try to make given reg the base */
    EAH_NOTBASE  = 2            /* try _not_ to make reg the base */
};

typedef struct {                /* operand to an instruction */
    int32_t type;               /* type of operand */
    int addr_size;              /* 0 means default; 16; 32; 64 */
    enum reg_enum basereg, indexreg; /* address registers */
    int scale;                  /* index scale */
    int hintbase;
    enum eval_hint hinttype;    /* hint as to real base register */
    int32_t segment;            /* immediate segment, if needed */
    int64_t offset;             /* any immediate number */
    int32_t wrt;                /* segment base it's relative to */
    int eaflags;                /* special EA flags */
    int opflags;                /* see OPFLAG_* defines below */
} operand;

#define OPFLAG_FORWARD          1       /* operand is a forward reference */
#define OPFLAG_EXTERN           2       /* operand is an external reference */

typedef struct extop {          /* extended operand */
    struct extop *next;         /* linked list */
    int32_t type;               /* defined above */
    char *stringval;          /* if it's a string, then here it is */
    int stringlen;              /* ... and here's how long it is */
    int32_t segment;            /* if it's a number/address, then... */
    int64_t offset;             /* ... it's given here ... */
    int32_t wrt;                /* ... and here */
} extop;

#define MAXPREFIX 4
#define MAX_OPERANDS 4

typedef struct {                /* an instruction itself */
    char *label;              /* the label defined, or NULL */
    enum prefixes prefixes[MAXPREFIX]; /* instruction prefixes, if any */
    int nprefix;                /* number of entries in above */
    enum opcode opcode;         /* the opcode - not just the string */
    enum ccode condition;       /* the condition code, if Jcc/SETcc */
    int operands;               /* how many operands? 0-3 
                                 * (more if db et al) */
    operand oprs[MAX_OPERANDS]; /* the operands, defined as above */
    extop *eops;                /* extended operands */
    int eops_float;             /* true if DD and floating */
    int32_t times;              /* repeat count (TIMES prefix) */
    int forw_ref;               /* is there a forward reference? */
    int rex;                    /* Special REX Prefix */
    int drexdst;                /* Destination register for DREX suffix */
} insn;

enum geninfo { GI_SWITCH };
/*
 * ------------------------------------------------------------
 * The data structure defining an output format driver, and the
 * interfaces to the functions therein.
 * ------------------------------------------------------------
 */

struct ofmt {
    /*
     * This is a short (one-liner) description of the type of
     * output generated by the driver.
     */
    const char *fullname;

    /*
     * This is a single keyword used to select the driver.
     */
    const char *shortname;
    

    /*
     * this is reserved for out module specific help.
     * It is set to NULL in all the out modules and is not implemented
     * in the main program
     */
    const char *helpstring;

    /*
     * this is a pointer to the first element of the debug information
     */
    struct dfmt **debug_formats;

    /*
     * and a pointer to the element that is being used
     * note: this is set to the default at compile time and changed if the
     * -F option is selected.  If developing a set of new debug formats for
     * an output format, be sure to set this to whatever default you want
     *
     */
    struct dfmt *current_dfmt;

    /*
     * This, if non-NULL, is a NULL-terminated list of `char *'s
     * pointing to extra standard macros supplied by the object
     * format (e.g. a sensible initial default value of __SECT__,
     * and user-level equivalents for any format-specific
     * directives).
     */
    const char **stdmac;

    /*
     * This procedure is called at the start of an output session.
     * It tells the output format what file it will be writing to,
     * what routine to report errors through, and how to interface
     * to the label manager and expression evaluator if necessary.
     * It also gives it a chance to do other initialisation.
     */
    void (*init) (FILE * fp, efunc error, ldfunc ldef, evalfunc eval);

    /*
     * This procedure is called to pass generic information to the
     * object file.  The first parameter gives the information type
     * (currently only command line switches)
     * and the second parameter gives the value.  This function returns
     * 1 if recognized, 0 if unrecognized
     */
    int (*setinfo) (enum geninfo type, char **string);

    /*
     * This procedure is called by assemble() to write actual
     * generated code or data to the object file. Typically it
     * doesn't have to actually _write_ it, just store it for
     * later.
     *
     * The `type' argument specifies the type of output data, and
     * usually the size as well: its contents are described below.
     */
    void (*output) (int32_t segto, const void *data, uint32_t type,
                    int32_t segment, int32_t wrt);

    /*
     * This procedure is called once for every symbol defined in
     * the module being assembled. It gives the name and value of
     * the symbol, in NASM's terms, and indicates whether it has
     * been declared to be global. Note that the parameter "name",
     * when passed, will point to a piece of static storage
     * allocated inside the label manager - it's safe to keep using
     * that pointer, because the label manager doesn't clean up
     * until after the output driver has.
     *
     * Values of `is_global' are: 0 means the symbol is local; 1
     * means the symbol is global; 2 means the symbol is common (in
     * which case `offset' holds the _size_ of the variable).
     * Anything else is available for the output driver to use
     * internally.
     *
     * This routine explicitly _is_ allowed to call the label
     * manager to define further symbols, if it wants to, even
     * though it's been called _from_ the label manager. That much
     * re-entrancy is guaranteed in the label manager. However, the
     * label manager will in turn call this routine, so it should
     * be prepared to be re-entrant itself.
     *
     * The `special' parameter contains special information passed
     * through from the command that defined the label: it may have
     * been an EXTERN, a COMMON or a GLOBAL. The distinction should
     * be obvious to the output format from the other parameters.
     */
    void (*symdef) (char *name, int32_t segment, int32_t offset, int is_global,
                    char *special);

    /*
     * This procedure is called when the source code requests a
     * segment change. It should return the corresponding segment
     * _number_ for the name, or NO_SEG if the name is not a valid
     * segment name.
     *
     * It may also be called with NULL, in which case it is to
     * return the _default_ section number for starting assembly in.
     *
     * It is allowed to modify the string it is given a pointer to.
     *
     * It is also allowed to specify a default instruction size for
     * the segment, by setting `*bits' to 16 or 32. Or, if it
     * doesn't wish to define a default, it can leave `bits' alone.
     */
    int32_t (*section) (char *name, int pass, int *bits);

    /*
     * This procedure is called to modify the segment base values
     * returned from the SEG operator. It is given a segment base
     * value (i.e. a segment value with the low bit set), and is
     * required to produce in return a segment value which may be
     * different. It can map segment bases to absolute numbers by
     * means of returning SEG_ABS types.
     *
     * It should return NO_SEG if the segment base cannot be
     * determined; the evaluator (which calls this routine) is
     * responsible for throwing an error condition if that occurs
     * in pass two or in a critical expression.
     */
    int32_t (*segbase) (int32_t segment);

    /*
     * This procedure is called to allow the output driver to
     * process its own specific directives. When called, it has the
     * directive word in `directive' and the parameter string in
     * `value'. It is called in both assembly passes, and `pass'
     * will be either 1 or 2.
     *
     * This procedure should return zero if it does not _recognise_
     * the directive, so that the main program can report an error.
     * If it recognises the directive but then has its own errors,
     * it should report them itself and then return non-zero. It
     * should also return non-zero if it correctly processes the
     * directive.
     */
    int (*directive) (char *directive, char *value, int pass);

    /*
     * This procedure is called before anything else - even before
     * the "init" routine - and is passed the name of the input
     * file from which this output file is being generated. It
     * should return its preferred name for the output file in
     * `outname', if outname[0] is not '\0', and do nothing to
     * `outname' otherwise. Since it is called before the driver is
     * properly initialized, it has to be passed its error handler
     * separately.
     *
     * This procedure may also take its own copy of the input file
     * name for use in writing the output file: it is _guaranteed_
     * that it will be called before the "init" routine.
     *
     * The parameter `outname' points to an area of storage
     * guaranteed to be at least FILENAME_MAX in size.
     */
    void (*filename) (char *inname, char *outname, efunc error);

    /*
     * This procedure is called after assembly finishes, to allow
     * the output driver to clean itself up and free its memory.
     * Typically, it will also be the point at which the object
     * file actually gets _written_.
     *
     * One thing the cleanup routine should always do is to close
     * the output file pointer.
     */
    void (*cleanup) (int debuginfo);
};

/*
 * values for the `type' parameter to an output function. Each one
 * must have the actual number of _bytes_ added to it.
 *
 * Exceptions are OUT_RELxADR, which denote an x-byte relocation
 * which will be a relative jump. For this we need to know the
 * distance in bytes from the start of the relocated record until
 * the end of the containing instruction. _This_ is what is stored
 * in the size part of the parameter, in this case.
 *
 * Also OUT_RESERVE denotes reservation of N bytes of BSS space,
 * and the contents of the "data" parameter is irrelevant.
 *
 * The "data" parameter for the output function points to a "int32_t",
 * containing the address in question, unless the type is
 * OUT_RAWDATA, in which case it points to an "uint8_t"
 * array.
 */
#define OUT_RAWDATA 0x00000000UL
#define OUT_ADDRESS 0x10000000UL
#define OUT_REL2ADR 0x20000000UL
#define OUT_REL4ADR 0x30000000UL
#define OUT_RESERVE 0x40000000UL
#define OUT_TYPMASK 0xF0000000UL
#define OUT_SIZMASK 0x0FFFFFFFUL

/*
 * ------------------------------------------------------------
 * The data structure defining a debug format driver, and the
 * interfaces to the functions therein.
 * ------------------------------------------------------------
 */

struct dfmt {

    /*
     * This is a short (one-liner) description of the type of
     * output generated by the driver.
     */
    const char *fullname;

    /*
     * This is a single keyword used to select the driver.
     */
    const char *shortname;

    /*
     * init - called initially to set up local pointer to object format, 
     * void pointer to implementation defined data, file pointer (which
     * probably won't be used, but who knows?), and error function.
     */
    void (*init) (struct ofmt * of, void *id, FILE * fp, efunc error);

    /*
     * linenum - called any time there is output with a change of
     * line number or file.
     */
    void (*linenum) (const char *filename, int32_t linenumber, int32_t segto);

    /*
     * debug_deflabel - called whenever a label is defined. Parameters
     * are the same as to 'symdef()' in the output format. This function
     * would be called before the output format version.
     */

    void (*debug_deflabel) (char *name, int32_t segment, int32_t offset,
                            int is_global, char *special);
    /*
     * debug_directive - called whenever a DEBUG directive other than 'LINE'
     * is encountered. 'directive' contains the first parameter to the
     * DEBUG directive, and params contains the rest. For example,
     * 'DEBUG VAR _somevar:int' would translate to a call to this
     * function with 'directive' equal to "VAR" and 'params' equal to 
     * "_somevar:int".
     */
    void (*debug_directive) (const char *directive, const char *params);

    /*
     * typevalue - called whenever the assembler wishes to register a type
     * for the last defined label.  This routine MUST detect if a type was
     * already registered and not re-register it.
     */
    void (*debug_typevalue) (int32_t type);

    /*
     * debug_output - called whenever output is required
     * 'type' is the type of info required, and this is format-specific
     */
    void (*debug_output) (int type, void *param);

    /*
     * cleanup - called after processing of file is complete
     */
    void (*cleanup) (void);

};
/*
 * The type definition macros
 * for debugging
 *
 * low 3 bits: reserved
 * next 5 bits: type
 * next 24 bits: number of elements for arrays (0 for labels)
 */

#define TY_UNKNOWN 0x00
#define TY_LABEL   0x08
#define TY_BYTE    0x10
#define TY_WORD    0x18
#define TY_DWORD   0x20
#define TY_FLOAT   0x28
#define TY_QWORD   0x30
#define TY_TBYTE   0x38
#define TY_OWORD   0x40
#define TY_COMMON  0xE0
#define TY_SEG     0xE8
#define TY_EXTERN  0xF0
#define TY_EQU     0xF8

#define TYM_TYPE(x) ((x) & 0xF8)
#define TYM_ELEMENTS(x) (((x) & 0xFFFFFF00) >> 8)

#define TYS_ELEMENTS(x)  ((x) << 8)

/*
 * -----
 * Special tokens
 * -----
 */

enum special_tokens {
    S_ABS, S_BYTE, S_DWORD, S_FAR, S_LONG, S_NEAR, S_NOSPLIT,
    S_OWORD, S_QWORD, S_REL, S_SHORT, S_STRICT, S_TO, S_TWORD, S_WORD
};

/*
 * -----
 * Other
 * -----
 */

/*
 * This is a useful #define which I keep meaning to use more often:
 * the number of elements of a statically defined array.
 */

#define elements(x)     ( sizeof(x) / sizeof(*(x)) )

/*
 * -----
 * Global modes
 * -----
 */

/*
 * This declaration passes the "pass" number to all other modules
 * "pass0" assumes the values: 0, 0, ..., 0, 1, 2
 * where 0 = optimizing pass
 *       1 = pass 1
 *       2 = pass 2
 */

extern int pass0;

extern int tasm_compatible_mode;
extern int optimizing;
extern int globalbits;          /* 16, 32 or 64-bit mode */
extern int globalrel;           /* default to relative addressing? */
extern int maxbits;             /* max bits supported by output */

#endif