labels.c

   1 /* labels.c  label handling for the Netwide Assembler
   2  *
   3  * The Netwide Assembler is copyright (C) 1996 Simon Tatham and
   4  * Julian Hall. All rights reserved. The software is
   5  * redistributable under the licence given in the file "Licence"
   6  * distributed in the NASM archive.
   7  */
   8
   9 #include <stdio.h>
  10 #include <string.h>
  11 #include <stdlib.h>
  12 #include "nasm.h"
  13 #include "nasmlib.h"
  14
  15 /*
  16  * A local label is one that begins with exactly one period. Things
  17  * that begin with _two_ periods are NASM-specific things.
  18  *
  19  * If TASM compatibility is enabled, a local label can also begin with
  20  * @@, so @@local is a TASM compatible local label. Note that we only
  21  * check for the first @ symbol, although TASM requires both.
  22  */
  23 #define islocal(l)                                              \
  24         (tasm_compatible_mode ?                                 \
  25         (((l)[0] == '.' || (l)[0] == '@') && (l)[1] != '.') :   \
  26         ((l)[0] == '.' && (l)[1] != '.'))
  27 #define islocalchar(c)                                          \
  28         (tasm_compatible_mode ?                                  \
  29         ((c) == '.' || (c) == '@') :                            \
  30         ((c) == '.'))
  31
  32 #define LABEL_BLOCK  32               /* no. of labels/block */
  33 #define LBLK_SIZE    (LABEL_BLOCK*sizeof(union label))
  34 #define LABEL_HASHES 37                       /* no. of hash table entries */
  35
  36 #define END_LIST -3                       /* don't clash with NO_SEG! */
  37 #define END_BLOCK -2
  38 #define BOGUS_VALUE -4
  39
  40 #define PERMTS_SIZE  4096               /* size of text blocks */
  41 #if (PERMTS_SIZE > IDLEN_MAX)
  42 #error "IPERMTS_SIZE must be less than or equal to IDLEN_MAX"
  43 #endif
  44
  45 /* values for label.defn.is_global */
  46 #define DEFINED_BIT 1
  47 #define GLOBAL_BIT 2
  48 #define EXTERN_BIT 4
  49
  50 #define NOT_DEFINED_YET 0
  51 #define TYPE_MASK 3
  52 #define LOCAL_SYMBOL (DEFINED_BIT)
  53 #define GLOBAL_PLACEHOLDER (GLOBAL_BIT)
  54 #define GLOBAL_SYMBOL (DEFINED_BIT|GLOBAL_BIT)
  55
  56 union label {                               /* actual label structures */
  57     struct {
  58         long segment, offset;
  59         char *label, *special;
  60         int is_global, is_norm;
  61     } defn;
  62     struct {
  63         long movingon, dummy;
  64         union label *next;
  65     } admin;
  66 };
  67
  68 struct permts {                               /* permanent text storage */
  69     struct permts *next;               /* for the linked list */
  70     int size, usage;                       /* size and used space in ... */
  71     char data[PERMTS_SIZE];               /* ... the data block itself */
  72 };
  73
  74 extern int global_offset_changed;   /* defined in nasm.c */
  75
  76 static union label *ltab[LABEL_HASHES];/* using a hash table */
  77 static union label *lfree[LABEL_HASHES];/* pointer into the above */
  78 static struct permts *perm_head;      /* start of perm. text storage */
  79 static struct permts *perm_tail;      /* end of perm. text storage */
  80
  81 static void init_block (union label *blk);
  82 static char *perm_copy (char *string1, char *string2);
  83
  84 static char *prevlabel;
  85
  86 static int initialised = FALSE;
  87
  88 char lprefix[PREFIX_MAX] = {0};
  89 char lpostfix[PREFIX_MAX] = {0};
  90
  91 /*
  92  * Internal routine: finds the `union label' corresponding to the
  93  * given label name. Creates a new one, if it isn't found, and if
  94  * `create' is TRUE.
  95  */
  96 static union label *find_label (char *label, int create)
  97 {
  98     int hash = 0;
  99     char *p, *prev;
 100     int prevlen;
 101     union label *lptr;
 102
 103     if (islocal(label))
 104         prev = prevlabel;
 105     else
 106         prev = "";
 107     prevlen = strlen(prev);
 108     p = prev;
 109     while (*p) hash += *p++;
 110     p = label;
 111     while (*p) hash += *p++;
 112     hash %= LABEL_HASHES;
 113     lptr = ltab[hash];
 114     while (lptr->admin.movingon != END_LIST) {
 115         if (lptr->admin.movingon == END_BLOCK) {
 116             lptr = lptr->admin.next;
 117             if (!lptr)
 118                 break;
 119         }
 120         if (!strncmp(lptr->defn.label, prev, prevlen) &&
 121             !strcmp(lptr->defn.label+prevlen, label))
 122             return lptr;
 123         lptr++;
 124     }
 125     if (create) {
 126         if (lfree[hash]->admin.movingon == END_BLOCK) {
 127             /*
 128              * must allocate a new block
 129              */
 130             lfree[hash]->admin.next = (union label *) nasm_malloc (LBLK_SIZE);
 131             lfree[hash] = lfree[hash]->admin.next;
 132             init_block(lfree[hash]);
 133         }
 134
 135         lfree[hash]->admin.movingon = BOGUS_VALUE;
 136         lfree[hash]->defn.label = perm_copy (prev, label);
 137         lfree[hash]->defn.special = NULL;
 138         lfree[hash]->defn.is_global = NOT_DEFINED_YET;
 139         return lfree[hash]++;
 140     }
 141     else
 142         return NULL;
 143 }
 144
 145 int lookup_label (char *label, long *segment, long *offset)
 146 {
 147     union label *lptr;
 148
 149     if (!initialised)
 150         return 0;
 151
 152     lptr = find_label (label, 0);
 153     if (lptr && (lptr->defn.is_global & DEFINED_BIT)) {
 154         *segment = lptr->defn.segment;
 155         *offset = lptr->defn.offset;
 156         return 1;
 157     }
 158     else
 159         return 0;
 160 }
 161
 162 int is_extern (char *label)
 163 {
 164     union label *lptr;
 165
 166     if (!initialised)
 167         return 0;
 168
 169     lptr = find_label (label, 0);
 170     if (lptr && (lptr->defn.is_global & EXTERN_BIT))
 171         return 1;
 172     else
 173         return 0;
 174 }
 175
 176 void redefine_label (char *label, long segment, long offset, char *special,
 177                    int is_norm, int isextrn, struct ofmt *ofmt, efunc error)
 178 {
 179     union label *lptr;
 180     int exi;
 181
 182     /* This routine possibly ought to check for phase errors.  Most assemblers
 183      * check for phase errors at this point.  I don't know whether phase errors
 184      * are even possible, nor whether they are checked somewhere else
 185      */
 186
 187     (void) segment;  /* Don't warn that this parameter is unused */
 188     (void) special;  /* Don't warn that this parameter is unused */
 189     (void) is_norm;  /* Don't warn that this parameter is unused */
 190     (void) isextrn;  /* Don't warn that this parameter is unused */
 191     (void) ofmt;     /* Don't warn that this parameter is unused */
 192
 193 #ifdef DEBUG
 194 #if DEBUG<3
 195     if (!strncmp(label, "debugdump", 9))
 196 #endif
 197         error(ERR_DEBUG, "redefine_label (%s, %ld, %08lx, %s, %d, %d)",
 198                 label, segment, offset, special, is_norm, isextrn);
 199 #endif
 200
 201     lptr = find_label (label, 1);
 202     if (!lptr)
 203         error (ERR_PANIC, "can't find label `%s' on pass two", label);
 204
 205     if (!islocal(label)) {
 206         if (!islocalchar(*label) && lptr->defn.is_norm)
 207             prevlabel = lptr->defn.label;
 208     }
 209
 210     global_offset_changed |= (lptr->defn.offset != offset);
 211     lptr->defn.offset = offset;
 212
 213 if (pass0 == 1) {
 214     exi = !!(lptr->defn.is_global & GLOBAL_BIT);
 215     if (exi)
 216     {
 217         char *xsymbol;
 218         int slen;
 219         slen = strlen(lprefix);
 220         slen += strlen(lptr->defn.label);
 221         slen += strlen(lpostfix);
 222         slen++; /* room for that null char */
 223         xsymbol = nasm_malloc(slen);
 224         snprintf(xsymbol,slen,"%s%s%s",lprefix,lptr->defn.label,lpostfix);
 225
 226         ofmt->symdef (xsymbol, segment, offset, exi,
 227                 special ? special : lptr->defn.special);
 228         ofmt->current_dfmt->debug_deflabel (xsymbol, segment, offset, exi,
 229                 special ? special : lptr->defn.special);
 230 /**     nasm_free(xsymbol);  ! outobj.c stores the pointer; ouch!!! **/
 231     }
 232     else
 233     {
 234         if ( (lptr->defn.is_global & (GLOBAL_BIT|EXTERN_BIT)) != EXTERN_BIT ) {
 235         ofmt->symdef (lptr->defn.label, segment, offset, exi,
 236                 special ? special : lptr->defn.special);
 237         ofmt->current_dfmt->debug_deflabel (label, segment, offset, exi,
 238                 special ? special : lptr->defn.special);
 239         }
 240     }
 241 } /* if (pass0 == 1) */
 242
 243 }
 244
 245 void define_label (char *label, long segment, long offset, char *special,
 246                    int is_norm, int isextrn, struct ofmt *ofmt, efunc error)
 247 {
 248     union label *lptr;
 249     int exi;
 250
 251 #ifdef DEBUG
 252 #if DEBUG<3
 253     if (!strncmp(label, "debugdump", 9))
 254 #endif
 255         error(ERR_DEBUG, "define_label (%s, %ld, %08lx, %s, %d, %d)",
 256                 label, segment, offset, special, is_norm, isextrn);
 257 #endif
 258     lptr = find_label (label, 1);
 259     if (lptr->defn.is_global & DEFINED_BIT) {
 260         error(ERR_NONFATAL, "symbol `%s' redefined", label);
 261         return;
 262     }
 263     lptr->defn.is_global |= DEFINED_BIT;
 264     if (isextrn)
 265         lptr->defn.is_global |= EXTERN_BIT;
 266
 267     if (!islocalchar(label[0]) && is_norm)    /* not local, but not special either */
 268         prevlabel = lptr->defn.label;
 269     else if (islocal(label) && !*prevlabel) {
 270         error(ERR_NONFATAL, "attempt to define a local label before any"
 271               " non-local labels");
 272         }
 273
 274     lptr->defn.segment = segment;
 275     lptr->defn.offset = offset;
 276     lptr->defn.is_norm = (!islocalchar(label[0]) && is_norm);
 277
 278 if (pass0 == 1 || (!is_norm && !isextrn && (segment&1))) {
 279     exi = !!(lptr->defn.is_global & GLOBAL_BIT);
 280     if (exi)
 281     {
 282         char *xsymbol;
 283         int slen;
 284         slen = strlen(lprefix);
 285         slen += strlen(lptr->defn.label);
 286         slen += strlen(lpostfix);
 287         slen++; /* room for that null char */
 288         xsymbol = nasm_malloc(slen);
 289         snprintf(xsymbol,slen,"%s%s%s",lprefix,lptr->defn.label,lpostfix);
 290
 291         ofmt->symdef (xsymbol, segment, offset, exi,
 292                 special ? special : lptr->defn.special);
 293         ofmt->current_dfmt->debug_deflabel (xsymbol, segment, offset, exi,
 294                 special ? special : lptr->defn.special);
 295 /**     nasm_free(xsymbol);  ! outobj.c stores the pointer; ouch!!! **/
 296     }
 297     else
 298     {
 299         if ( (lptr->defn.is_global & (GLOBAL_BIT|EXTERN_BIT)) != EXTERN_BIT ) {
 300         ofmt->symdef (lptr->defn.label, segment, offset, exi,
 301                 special ? special : lptr->defn.special);
 302         ofmt->current_dfmt->debug_deflabel (label, segment, offset, exi,
 303                 special ? special : lptr->defn.special);
 304         }
 305     }
 306 } /* if (pass0 == 1) */
 307 }
 308
 309 void define_common (char *label, long segment, long size, char *special,
 310                     struct ofmt *ofmt, efunc error)
 311 {
 312     union label *lptr;
 313
 314     lptr = find_label (label, 1);
 315     if (lptr->defn.is_global & DEFINED_BIT) {
 316         error(ERR_NONFATAL, "symbol `%s' redefined", label);
 317         return;
 318     }
 319     lptr->defn.is_global |= DEFINED_BIT;
 320
 321     if (!islocalchar(label[0]))        /* not local, but not special either */
 322         prevlabel = lptr->defn.label;
 323     else
 324         error(ERR_NONFATAL, "attempt to define a local label as a "
 325               "common variable");
 326
 327     lptr->defn.segment = segment;
 328     lptr->defn.offset = 0;
 329
 330     ofmt->symdef (lptr->defn.label, segment, size, 2,
 331                   special ? special : lptr->defn.special);
 332     ofmt->current_dfmt->debug_deflabel(lptr->defn.label, segment, size, 2,
 333                   special ? special : lptr->defn.special);
 334 }
 335
 336 void declare_as_global (char *label, char *special, efunc error)
 337 {
 338     union label *lptr;
 339
 340     if (islocal(label)) {
 341         error(ERR_NONFATAL, "attempt to declare local symbol `%s' as"
 342               " global", label);
 343         return;
 344     }
 345     lptr = find_label (label, 1);
 346     switch (lptr->defn.is_global & TYPE_MASK) {
 347       case NOT_DEFINED_YET:
 348         lptr->defn.is_global = GLOBAL_PLACEHOLDER;
 349         lptr->defn.special = special ? perm_copy(special, "") : NULL;
 350         break;
 351       case GLOBAL_PLACEHOLDER:               /* already done: silently ignore */
 352       case GLOBAL_SYMBOL:
 353         break;
 354       case LOCAL_SYMBOL:
 355         if (!lptr->defn.is_global & EXTERN_BIT)
 356             error(ERR_NONFATAL, "symbol `%s': GLOBAL directive must"
 357                   " appear before symbol definition", label);
 358         break;
 359     }
 360 }
 361
 362 int init_labels (void)
 363 {
 364     int i;
 365
 366     for (i=0; i<LABEL_HASHES; i++) {
 367         ltab[i] = (union label *) nasm_malloc (LBLK_SIZE);
 368         if (!ltab[i])
 369             return -1;                       /* can't initialise, panic */
 370         init_block (ltab[i]);
 371         lfree[i] = ltab[i];
 372     }
 373
 374     perm_head =
 375         perm_tail = (struct permts *) nasm_malloc (sizeof(struct permts));
 376
 377     if (!perm_head)
 378             return -1;
 379
 380     perm_head->next = NULL;
 381     perm_head->size = PERMTS_SIZE;
 382     perm_head->usage = 0;
 383
 384     prevlabel = "";
 385
 386     initialised = TRUE;
 387
 388     return 0;
 389 }
 390
 391 void cleanup_labels (void)
 392 {
 393     int i;
 394
 395     initialised = FALSE;
 396
 397     for (i=0; i<LABEL_HASHES; i++) {
 398         union label *lptr, *lhold;
 399
 400         lptr = lhold = ltab[i];
 401
 402         while (lptr) {
 403             while (lptr->admin.movingon != END_BLOCK) lptr++;
 404             lptr = lptr->admin.next;
 405             nasm_free (lhold);
 406             lhold = lptr;
 407         }
 408     }
 409
 410     while (perm_head) {
 411         perm_tail = perm_head;
 412         perm_head = perm_head->next;
 413         nasm_free (perm_tail);
 414     }
 415 }
 416
 417 static void init_block (union label *blk)
 418 {
 419     int j;
 420
 421     for (j=0; j<LABEL_BLOCK-1; j++)
 422             blk[j].admin.movingon = END_LIST;
 423     blk[LABEL_BLOCK-1].admin.movingon = END_BLOCK;
 424     blk[LABEL_BLOCK-1].admin.next = NULL;
 425 }
 426
 427 static char *perm_copy (char *string1, char *string2)
 428 {
 429     char *p, *q;
 430     int len = strlen(string1)+strlen(string2)+1;
 431
 432     if (perm_tail->size - perm_tail->usage < len) {
 433         perm_tail->next = (struct permts *)nasm_malloc(sizeof(struct permts));
 434         perm_tail = perm_tail->next;
 435         perm_tail->next = NULL;
 436         perm_tail->size = PERMTS_SIZE;
 437         perm_tail->usage = 0;
 438     }
 439     p = q = perm_tail->data + perm_tail->usage;
 440     while ( (*q = *string1++) ) q++;
 441     while ( (*q++ = *string2++) ) ;
 442     perm_tail->usage = q - perm_tail->data;
 443
 444     return p;
 445 }
 446
 447 /*
 448  * Notes regarding bug involving redefinition of external segments.
 449  *
 450  * Up to and including v0.97, the following code didn't work. From 0.97
 451  * developers release 2 onwards, it will generate an error.
 452  *
 453  * EXTERN extlabel
 454  * newlabel EQU extlabel + 1
 455  *
 456  * The results of allowing this code through are that two import records
 457  * are generated, one for 'extlabel' and one for 'newlabel'.
 458  *
 459  * The reason for this is an inadequacy in the defined interface between
 460  * the label manager and the output formats. The problem lies in how the
 461  * output format driver tells that a label is an external label for which
 462  * a label import record must be produced. Most (all except bin?) produce
 463  * the record if the segment number of the label is not one of the internal
 464  * segments that the output driver is producing.
 465  *
 466  * A simple fix to this would be to make the output formats keep track of
 467  * which symbols they've produced import records for, and make them not
 468  * produce import records for segments that are already defined.
 469  *
 470  * The best way, which is slightly harder but reduces duplication of code
 471  * and should therefore make the entire system smaller and more stable is
 472  * to change the interface between assembler, define_label(), and
 473  * the output module. The changes that are needed are:
 474  *
 475  * The semantics of the 'isextern' flag passed to define_label() need
 476  * examining. This information may or may not tell us what we need to
 477  * know (ie should we be generating an import record at this point for this
 478  * label). If these aren't the semantics, the semantics should be changed
 479  * to this.
 480  *
 481  * The output module interface needs changing, so that the `isextern' flag
 482  * is passed to the module, so that it can be easily tested for.
 483  */