labels.c   [plain text]


/* labels.c  label handling for the Netwide Assembler
 *
 * 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.
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "nasm.h"
#include "nasmlib.h"

/*
 * A local label is one that begins with exactly one period. Things
 * that begin with _two_ periods are NASM-specific things.
 *
 * If TASM compatibility is enabled, a local label can also begin with
 * @@, so @@local is a TASM compatible local label. Note that we only
 * check for the first @ symbol, although TASM requires both.
 */
#define islocal(l)                                              \
	(tasm_compatible_mode ?					\
	(((l)[0] == '.' || (l)[0] == '@') && (l)[1] != '.') :   \
	((l)[0] == '.' && (l)[1] != '.'))
#define islocalchar(c)						\
	(tasm_compatible_mode ?                                  \
	((c) == '.' || (c) == '@') :                            \
	((c) == '.'))

#define LABEL_BLOCK  32         /* no. of labels/block */
#define LBLK_SIZE    (LABEL_BLOCK*sizeof(union label))
#define LABEL_HASHES 37         /* no. of hash table entries */

#define END_LIST -3             /* don't clash with NO_SEG! */
#define END_BLOCK -2
#define BOGUS_VALUE -4

#define PERMTS_SIZE  4096       /* size of text blocks */
#if (PERMTS_SIZE > IDLEN_MAX)
#error "IPERMTS_SIZE must be less than or equal to IDLEN_MAX"
#endif

/* values for label.defn.is_global */
#define DEFINED_BIT 1
#define GLOBAL_BIT 2
#define EXTERN_BIT 4

#define NOT_DEFINED_YET 0
#define TYPE_MASK 3
#define LOCAL_SYMBOL (DEFINED_BIT)
#define GLOBAL_PLACEHOLDER (GLOBAL_BIT)
#define GLOBAL_SYMBOL (DEFINED_BIT|GLOBAL_BIT)

union label {                   /* actual label structures */
    struct {
        long segment, offset;
        char *label, *special;
        int is_global, is_norm;
    } defn;
    struct {
        long movingon, dummy;
        union label *next;
    } admin;
};

struct permts {                 /* permanent text storage */
    struct permts *next;        /* for the linked list */
    int size, usage;            /* size and used space in ... */
    char data[PERMTS_SIZE];     /* ... the data block itself */
};

extern int global_offset_changed;       /* defined in nasm.c */

static union label *ltab[LABEL_HASHES]; /* using a hash table */
static union label *lfree[LABEL_HASHES];        /* pointer into the above */
static struct permts *perm_head;        /* start of perm. text storage */
static struct permts *perm_tail;        /* end of perm. text storage */

static void init_block(union label *blk);
static char *perm_copy(char *string1, char *string2);

static char *prevlabel;

static int initialised = FALSE;

char lprefix[PREFIX_MAX] = { 0 };
char lpostfix[PREFIX_MAX] = { 0 };

/*
 * Internal routine: finds the `union label' corresponding to the
 * given label name. Creates a new one, if it isn't found, and if
 * `create' is TRUE.
 */
static union label *find_label(char *label, int create)
{
    int hash = 0;
    char *p, *prev;
    int prevlen;
    union label *lptr;

    if (islocal(label))
        prev = prevlabel;
    else
        prev = "";
    prevlen = strlen(prev);
    p = prev;
    while (*p)
        hash += *p++;
    p = label;
    while (*p)
        hash += *p++;
    hash %= LABEL_HASHES;
    lptr = ltab[hash];
    while (lptr->admin.movingon != END_LIST) {
        if (lptr->admin.movingon == END_BLOCK) {
            lptr = lptr->admin.next;
            if (!lptr)
                break;
        }
        if (!strncmp(lptr->defn.label, prev, prevlen) &&
            !strcmp(lptr->defn.label + prevlen, label))
            return lptr;
        lptr++;
    }
    if (create) {
        if (lfree[hash]->admin.movingon == END_BLOCK) {
            /*
             * must allocate a new block
             */
            lfree[hash]->admin.next =
                (union label *)nasm_malloc(LBLK_SIZE);
            lfree[hash] = lfree[hash]->admin.next;
            init_block(lfree[hash]);
        }

        lfree[hash]->admin.movingon = BOGUS_VALUE;
        lfree[hash]->defn.label = perm_copy(prev, label);
        lfree[hash]->defn.special = NULL;
        lfree[hash]->defn.is_global = NOT_DEFINED_YET;
        return lfree[hash]++;
    } else
        return NULL;
}

int lookup_label(char *label, long *segment, long *offset)
{
    union label *lptr;

    if (!initialised)
        return 0;

    lptr = find_label(label, 0);
    if (lptr && (lptr->defn.is_global & DEFINED_BIT)) {
        *segment = lptr->defn.segment;
        *offset = lptr->defn.offset;
        return 1;
    } else
        return 0;
}

int is_extern(char *label)
{
    union label *lptr;

    if (!initialised)
        return 0;

    lptr = find_label(label, 0);
    if (lptr && (lptr->defn.is_global & EXTERN_BIT))
        return 1;
    else
        return 0;
}

void redefine_label(char *label, long segment, long offset, char *special,
                    int is_norm, int isextrn, struct ofmt *ofmt,
                    efunc error)
{
    union label *lptr;
    int exi;

    /* This routine possibly ought to check for phase errors.  Most assemblers
     * check for phase errors at this point.  I don't know whether phase errors
     * are even possible, nor whether they are checked somewhere else
     */

    (void)segment;              /* Don't warn that this parameter is unused */
    (void)special;              /* Don't warn that this parameter is unused */
    (void)is_norm;              /* Don't warn that this parameter is unused */
    (void)isextrn;              /* Don't warn that this parameter is unused */
    (void)ofmt;                 /* Don't warn that this parameter is unused */

#ifdef DEBUG
#if DEBUG<3
    if (!strncmp(label, "debugdump", 9))
#endif
        error(ERR_DEBUG, "redefine_label (%s, %ld, %08lx, %s, %d, %d)",
              label, segment, offset, special, is_norm, isextrn);
#endif

    lptr = find_label(label, 1);
    if (!lptr)
        error(ERR_PANIC, "can't find label `%s' on pass two", label);

    if (!islocal(label)) {
        if (!islocalchar(*label) && lptr->defn.is_norm)
            prevlabel = lptr->defn.label;
    }

    global_offset_changed |= (lptr->defn.offset != offset);
    lptr->defn.offset = offset;

    if (pass0 == 1) {
        exi = !!(lptr->defn.is_global & GLOBAL_BIT);
        if (exi) {
            char *xsymbol;
            int slen;
            slen = strlen(lprefix);
            slen += strlen(lptr->defn.label);
            slen += strlen(lpostfix);
            slen++;             /* room for that null char */
            xsymbol = nasm_malloc(slen);
            snprintf(xsymbol, slen, "%s%s%s", lprefix, lptr->defn.label,
                     lpostfix);

            ofmt->symdef(xsymbol, segment, offset, exi,
                         special ? special : lptr->defn.special);
            ofmt->current_dfmt->debug_deflabel(xsymbol, segment, offset,
                                               exi,
                                               special ? special : lptr->
                                               defn.special);
/**	nasm_free(xsymbol);  ! outobj.c stores the pointer; ouch!!! **/
        } else {
            if ((lptr->defn.is_global & (GLOBAL_BIT | EXTERN_BIT)) !=
                EXTERN_BIT) {
                ofmt->symdef(lptr->defn.label, segment, offset, exi,
                             special ? special : lptr->defn.special);
                ofmt->current_dfmt->debug_deflabel(label, segment, offset,
                                                   exi,
                                                   special ? special :
                                                   lptr->defn.special);
            }
        }
    }
    /* if (pass0 == 1) */
}

void define_label(char *label, long segment, long offset, char *special,
                  int is_norm, int isextrn, struct ofmt *ofmt, efunc error)
{
    union label *lptr;
    int exi;

#ifdef DEBUG
#if DEBUG<3
    if (!strncmp(label, "debugdump", 9))
#endif
        error(ERR_DEBUG, "define_label (%s, %ld, %08lx, %s, %d, %d)",
              label, segment, offset, special, is_norm, isextrn);
#endif
    lptr = find_label(label, 1);
    if (lptr->defn.is_global & DEFINED_BIT) {
        error(ERR_NONFATAL, "symbol `%s' redefined", label);
        return;
    }
    lptr->defn.is_global |= DEFINED_BIT;
    if (isextrn)
        lptr->defn.is_global |= EXTERN_BIT;

    if (!islocalchar(label[0]) && is_norm)      /* not local, but not special either */
        prevlabel = lptr->defn.label;
    else if (islocal(label) && !*prevlabel) {
        error(ERR_NONFATAL, "attempt to define a local label before any"
              " non-local labels");
    }

    lptr->defn.segment = segment;
    lptr->defn.offset = offset;
    lptr->defn.is_norm = (!islocalchar(label[0]) && is_norm);

    if (pass0 == 1 || (!is_norm && !isextrn && (segment & 1))) {
        exi = !!(lptr->defn.is_global & GLOBAL_BIT);
        if (exi) {
            char *xsymbol;
            int slen;
            slen = strlen(lprefix);
            slen += strlen(lptr->defn.label);
            slen += strlen(lpostfix);
            slen++;             /* room for that null char */
            xsymbol = nasm_malloc(slen);
            snprintf(xsymbol, slen, "%s%s%s", lprefix, lptr->defn.label,
                     lpostfix);

            ofmt->symdef(xsymbol, segment, offset, exi,
                         special ? special : lptr->defn.special);
            ofmt->current_dfmt->debug_deflabel(xsymbol, segment, offset,
                                               exi,
                                               special ? special : lptr->
                                               defn.special);
/**	nasm_free(xsymbol);  ! outobj.c stores the pointer; ouch!!! **/
        } else {
            if ((lptr->defn.is_global & (GLOBAL_BIT | EXTERN_BIT)) !=
                EXTERN_BIT) {
                ofmt->symdef(lptr->defn.label, segment, offset, exi,
                             special ? special : lptr->defn.special);
                ofmt->current_dfmt->debug_deflabel(label, segment, offset,
                                                   exi,
                                                   special ? special :
                                                   lptr->defn.special);
            }
        }
    }                           /* if (pass0 == 1) */
}

void define_common(char *label, long segment, long size, char *special,
                   struct ofmt *ofmt, efunc error)
{
    union label *lptr;

    lptr = find_label(label, 1);
    if (lptr->defn.is_global & DEFINED_BIT) {
        error(ERR_NONFATAL, "symbol `%s' redefined", label);
        return;
    }
    lptr->defn.is_global |= DEFINED_BIT;

    if (!islocalchar(label[0])) /* not local, but not special either */
        prevlabel = lptr->defn.label;
    else
        error(ERR_NONFATAL, "attempt to define a local label as a "
              "common variable");

    lptr->defn.segment = segment;
    lptr->defn.offset = 0;

    ofmt->symdef(lptr->defn.label, segment, size, 2,
                 special ? special : lptr->defn.special);
    ofmt->current_dfmt->debug_deflabel(lptr->defn.label, segment, size, 2,
                                       special ? special : lptr->defn.
                                       special);
}

void declare_as_global(char *label, char *special, efunc error)
{
    union label *lptr;

    if (islocal(label)) {
        error(ERR_NONFATAL, "attempt to declare local symbol `%s' as"
              " global", label);
        return;
    }
    lptr = find_label(label, 1);
    switch (lptr->defn.is_global & TYPE_MASK) {
    case NOT_DEFINED_YET:
        lptr->defn.is_global = GLOBAL_PLACEHOLDER;
        lptr->defn.special = special ? perm_copy(special, "") : NULL;
        break;
    case GLOBAL_PLACEHOLDER:   /* already done: silently ignore */
    case GLOBAL_SYMBOL:
        break;
    case LOCAL_SYMBOL:
        if (!lptr->defn.is_global & EXTERN_BIT)
            error(ERR_NONFATAL, "symbol `%s': GLOBAL directive must"
                  " appear before symbol definition", label);
        break;
    }
}

int init_labels(void)
{
    int i;

    for (i = 0; i < LABEL_HASHES; i++) {
        ltab[i] = (union label *)nasm_malloc(LBLK_SIZE);
        if (!ltab[i])
            return -1;          /* can't initialise, panic */
        init_block(ltab[i]);
        lfree[i] = ltab[i];
    }

    perm_head =
        perm_tail = (struct permts *)nasm_malloc(sizeof(struct permts));

    if (!perm_head)
        return -1;

    perm_head->next = NULL;
    perm_head->size = PERMTS_SIZE;
    perm_head->usage = 0;

    prevlabel = "";

    initialised = TRUE;

    return 0;
}

void cleanup_labels(void)
{
    int i;

    initialised = FALSE;

    for (i = 0; i < LABEL_HASHES; i++) {
        union label *lptr, *lhold;

        lptr = lhold = ltab[i];

        while (lptr) {
            while (lptr->admin.movingon != END_BLOCK)
                lptr++;
            lptr = lptr->admin.next;
            nasm_free(lhold);
            lhold = lptr;
        }
    }

    while (perm_head) {
        perm_tail = perm_head;
        perm_head = perm_head->next;
        nasm_free(perm_tail);
    }
}

static void init_block(union label *blk)
{
    int j;

    for (j = 0; j < LABEL_BLOCK - 1; j++)
        blk[j].admin.movingon = END_LIST;
    blk[LABEL_BLOCK - 1].admin.movingon = END_BLOCK;
    blk[LABEL_BLOCK - 1].admin.next = NULL;
}

static char *perm_copy(char *string1, char *string2)
{
    char *p, *q;
    int len = strlen(string1) + strlen(string2) + 1;

    if (perm_tail->size - perm_tail->usage < len) {
        perm_tail->next =
            (struct permts *)nasm_malloc(sizeof(struct permts));
        perm_tail = perm_tail->next;
        perm_tail->next = NULL;
        perm_tail->size = PERMTS_SIZE;
        perm_tail->usage = 0;
    }
    p = q = perm_tail->data + perm_tail->usage;
    while ((*q = *string1++))
        q++;
    while ((*q++ = *string2++)) ;
    perm_tail->usage = q - perm_tail->data;

    return p;
}

/*
 * Notes regarding bug involving redefinition of external segments.
 *
 * Up to and including v0.97, the following code didn't work. From 0.97
 * developers release 2 onwards, it will generate an error.
 *
 * EXTERN extlabel
 * newlabel EQU extlabel + 1
 *
 * The results of allowing this code through are that two import records
 * are generated, one for 'extlabel' and one for 'newlabel'.
 *
 * The reason for this is an inadequacy in the defined interface between
 * the label manager and the output formats. The problem lies in how the
 * output format driver tells that a label is an external label for which
 * a label import record must be produced. Most (all except bin?) produce
 * the record if the segment number of the label is not one of the internal
 * segments that the output driver is producing.
 *
 * A simple fix to this would be to make the output formats keep track of
 * which symbols they've produced import records for, and make them not
 * produce import records for segments that are already defined.
 *
 * The best way, which is slightly harder but reduces duplication of code
 * and should therefore make the entire system smaller and more stable is
 * to change the interface between assembler, define_label(), and
 * the output module. The changes that are needed are:
 *
 * The semantics of the 'isextern' flag passed to define_label() need
 * examining. This information may or may not tell us what we need to
 * know (ie should we be generating an import record at this point for this
 * label). If these aren't the semantics, the semantics should be changed
 * to this.
 *
 * The output module interface needs changing, so that the `isextern' flag
 * is passed to the module, so that it can be easily tested for.
 */