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 <inttypes.h>
  13
  14 #include "nasm.h"
  15 #include "nasmlib.h"
  16 #include "hashtbl.h"
  17
  18 /*
  19  * A local label is one that begins with exactly one period. Things
  20  * that begin with _two_ periods are NASM-specific things.
  21  *
  22  * If TASM compatibility is enabled, a local label can also begin with
  23  * @@, so @@local is a TASM compatible local label. Note that we only
  24  * check for the first @ symbol, although TASM requires both.
  25  */
  26 #define islocal(l)                                              \
  27         (tasm_compatible_mode ?                                 \
  28         (((l)[0] == '.' || (l)[0] == '@') && (l)[1] != '.') :   \
  29         ((l)[0] == '.' && (l)[1] != '.'))
  30 #define islocalchar(c)                                          \
  31         (tasm_compatible_mode ?                                  \
  32         ((c) == '.' || (c) == '@') :                            \
  33         ((c) == '.'))
  34
  35 #define LABEL_BLOCK  128        /* no. of labels/block */
  36 #define LBLK_SIZE    (LABEL_BLOCK*sizeof(union label))
  37
  38 #define END_LIST -3             /* don't clash with NO_SEG! */
  39 #define END_BLOCK -2
  40 #define BOGUS_VALUE -4
  41
  42 #define PERMTS_SIZE  4096       /* size of text blocks */
  43 #if (PERMTS_SIZE > IDLEN_MAX)
  44 #error "IPERMTS_SIZE must be less than or equal to IDLEN_MAX"
  45 #endif
  46
  47 /* values for label.defn.is_global */
  48 #define DEFINED_BIT 1
  49 #define GLOBAL_BIT 2
  50 #define EXTERN_BIT 4
  51
  52 #define NOT_DEFINED_YET 0
  53 #define TYPE_MASK 3
  54 #define LOCAL_SYMBOL (DEFINED_BIT)
  55 #define GLOBAL_PLACEHOLDER (GLOBAL_BIT)
  56 #define GLOBAL_SYMBOL (DEFINED_BIT|GLOBAL_BIT)
  57
  58 union label {                   /* actual label structures */
  59     struct {
  60         int32_t segment, offset;
  61         char *label, *special;
  62         int is_global, is_norm;
  63     } defn;
  64     struct {
  65         int32_t movingon, dummy;
  66         union label *next;
  67     } admin;
  68 };
  69
  70 struct permts {                 /* permanent text storage */
  71     struct permts *next;        /* for the linked list */
  72     int size, usage;            /* size and used space in ... */
  73     char data[PERMTS_SIZE];     /* ... the data block itself */
  74 };
  75
  76 extern int global_offset_changed;       /* defined in nasm.c */
  77
  78 static struct hash_table *ltab;         /* labels hash table */
  79 static union label *ldata;              /* all label data blocks */
  80 static union label *lfree;              /* labels free block */
  81 static struct permts *perm_head;        /* start of perm. text storage */
  82 static struct permts *perm_tail;        /* end of perm. text storage */
  83
  84 static void init_block(union label *blk);
  85 static char *perm_copy(const char *string);
  86
  87 static char *prevlabel;
  88
  89 static int initialized = FALSE;
  90
  91 char lprefix[PREFIX_MAX] = { 0 };
  92 char lpostfix[PREFIX_MAX] = { 0 };
  93
  94 /*
  95  * Internal routine: finds the `union label' corresponding to the
  96  * given label name. Creates a new one, if it isn't found, and if
  97  * `create' is TRUE.
  98  */
  99 static union label *find_label(char *label, int create)
 100 {
 101     char *prev;
 102     int prevlen, len;
 103     union label *lptr, **lpp;
 104     char label_str[IDLEN_MAX];
 105     struct hash_insert ip;
 106
 107     if (islocal(label)) {
 108         prev = prevlabel;
 109         prevlen = strlen(prev);
 110         len = strlen(label);
 111         if (prevlen+len >= IDLEN_MAX)
 112             return NULL;        /* Error... */
 113         memcpy(label_str, prev, prevlen);
 114         memcpy(label_str+prevlen, label, len+1);
 115         label = label_str;
 116     } else {
 117         prev = "";
 118         prevlen = 0;
 119     }
 120
 121     lpp = (union label **) hash_find(ltab, label, &ip);
 122     lptr = lpp ? *lpp : NULL;
 123
 124     if (lptr || !create)
 125         return lptr;
 126
 127     /* Create a new label... */
 128     if (lfree->admin.movingon == END_BLOCK) {
 129         /*
 130          * must allocate a new block
 131          */
 132         lfree->admin.next =
 133             (union label *)nasm_malloc(LBLK_SIZE);
 134         lfree = lfree->admin.next;
 135         init_block(lfree);
 136     }
 137
 138     lfree->admin.movingon = BOGUS_VALUE;
 139     lfree->defn.label = perm_copy(label);
 140     lfree->defn.special = NULL;
 141     lfree->defn.is_global = NOT_DEFINED_YET;
 142
 143     hash_add(&ip, lfree->defn.label, lfree);
 144     return lfree++;
 145 }
 146
 147 int lookup_label(char *label, int32_t *segment, int32_t *offset)
 148 {
 149     union label *lptr;
 150
 151     if (!initialized)
 152         return 0;
 153
 154     lptr = find_label(label, 0);
 155     if (lptr && (lptr->defn.is_global & DEFINED_BIT)) {
 156         *segment = lptr->defn.segment;
 157         *offset = lptr->defn.offset;
 158         return 1;
 159     } else
 160         return 0;
 161 }
 162
 163 int is_extern(char *label)
 164 {
 165     union label *lptr;
 166
 167     if (!initialized)
 168         return 0;
 169
 170     lptr = find_label(label, 0);
 171     if (lptr && (lptr->defn.is_global & EXTERN_BIT))
 172         return 1;
 173     else
 174         return 0;
 175 }
 176
 177 void redefine_label(char *label, int32_t segment, int32_t offset, char *special,
 178                     int is_norm, int isextrn, struct ofmt *ofmt,
 179                     efunc error)
 180 {
 181     union label *lptr;
 182     int exi;
 183
 184     /* This routine possibly ought to check for phase errors.  Most assemblers
 185      * check for phase errors at this point.  I don't know whether phase errors
 186      * are even possible, nor whether they are checked somewhere else
 187      */
 188
 189     (void)segment;              /* Don't warn that this parameter is unused */
 190     (void)special;              /* Don't warn that this parameter is unused */
 191     (void)is_norm;              /* Don't warn that this parameter is unused */
 192     (void)isextrn;              /* Don't warn that this parameter is unused */
 193     (void)ofmt;                 /* Don't warn that this parameter is unused */
 194
 195 #ifdef DEBUG
 196 #if DEBUG<3
 197     if (!strncmp(label, "debugdump", 9))
 198 #endif
 199         error(ERR_DEBUG, "redefine_label (%s, %ld, %08lx, %s, %d, %d)",
 200               label, segment, offset, special, is_norm, isextrn);
 201 #endif
 202
 203     lptr = find_label(label, 1);
 204     if (!lptr)
 205         error(ERR_PANIC, "can't find label `%s' on pass two", label);
 206
 207     if (!islocal(label)) {
 208         if (!islocalchar(*label) && lptr->defn.is_norm)
 209             prevlabel = lptr->defn.label;
 210     }
 211
 212     global_offset_changed |= (lptr->defn.offset != offset);
 213     lptr->defn.offset = offset;
 214
 215     if (pass0 == 1) {
 216         exi = !!(lptr->defn.is_global & GLOBAL_BIT);
 217         if (exi) {
 218             char *xsymbol;
 219             int slen;
 220             slen = strlen(lprefix);
 221             slen += strlen(lptr->defn.label);
 222             slen += strlen(lpostfix);
 223             slen++;             /* room for that null char */
 224             xsymbol = nasm_malloc(slen);
 225             snprintf(xsymbol, slen, "%s%s%s", lprefix, lptr->defn.label,
 226                      lpostfix);
 227
 228             ofmt->symdef(xsymbol, segment, offset, exi,
 229                          special ? special : lptr->defn.special);
 230             ofmt->current_dfmt->debug_deflabel(xsymbol, segment, offset,
 231                                                exi,
 232                                                special ? special : lptr->
 233                                                defn.special);
 234 /**     nasm_free(xsymbol);  ! outobj.c stores the pointer; ouch!!! **/
 235         } else {
 236             if ((lptr->defn.is_global & (GLOBAL_BIT | EXTERN_BIT)) !=
 237                 EXTERN_BIT) {
 238                 ofmt->symdef(lptr->defn.label, segment, offset, exi,
 239                              special ? special : lptr->defn.special);
 240                 ofmt->current_dfmt->debug_deflabel(label, segment, offset,
 241                                                    exi,
 242                                                    special ? special :
 243                                                    lptr->defn.special);
 244             }
 245         }
 246     }
 247     /* if (pass0 == 1) */
 248 }
 249
 250 void define_label(char *label, int32_t segment, int32_t offset, char *special,
 251                   int is_norm, int isextrn, struct ofmt *ofmt, efunc error)
 252 {
 253     union label *lptr;
 254     int exi;
 255
 256 #ifdef DEBUG
 257 #if DEBUG<3
 258     if (!strncmp(label, "debugdump", 9))
 259 #endif
 260         error(ERR_DEBUG, "define_label (%s, %ld, %08lx, %s, %d, %d)",
 261               label, segment, offset, special, is_norm, isextrn);
 262 #endif
 263     lptr = find_label(label, 1);
 264     if (lptr->defn.is_global & DEFINED_BIT) {
 265         error(ERR_NONFATAL, "symbol `%s' redefined", label);
 266         return;
 267     }
 268     lptr->defn.is_global |= DEFINED_BIT;
 269     if (isextrn)
 270         lptr->defn.is_global |= EXTERN_BIT;
 271
 272     if (!islocalchar(label[0]) && is_norm)      /* not local, but not special either */
 273         prevlabel = lptr->defn.label;
 274     else if (islocal(label) && !*prevlabel) {
 275         error(ERR_NONFATAL, "attempt to define a local label before any"
 276               " non-local labels");
 277     }
 278
 279     lptr->defn.segment = segment;
 280     lptr->defn.offset = offset;
 281     lptr->defn.is_norm = (!islocalchar(label[0]) && is_norm);
 282
 283     if (pass0 == 1 || (!is_norm && !isextrn && (segment & 1))) {
 284         exi = !!(lptr->defn.is_global & GLOBAL_BIT);
 285         if (exi) {
 286             char *xsymbol;
 287             int slen;
 288             slen = strlen(lprefix);
 289             slen += strlen(lptr->defn.label);
 290             slen += strlen(lpostfix);
 291             slen++;             /* room for that null char */
 292             xsymbol = nasm_malloc(slen);
 293             snprintf(xsymbol, slen, "%s%s%s", lprefix, lptr->defn.label,
 294                      lpostfix);
 295
 296             ofmt->symdef(xsymbol, segment, offset, exi,
 297                          special ? special : lptr->defn.special);
 298             ofmt->current_dfmt->debug_deflabel(xsymbol, segment, offset,
 299                                                exi,
 300                                                special ? special : lptr->
 301                                                defn.special);
 302 /**     nasm_free(xsymbol);  ! outobj.c stores the pointer; ouch!!! **/
 303         } else {
 304             if ((lptr->defn.is_global & (GLOBAL_BIT | EXTERN_BIT)) !=
 305                 EXTERN_BIT) {
 306                 ofmt->symdef(lptr->defn.label, segment, offset, exi,
 307                              special ? special : lptr->defn.special);
 308                 ofmt->current_dfmt->debug_deflabel(label, segment, offset,
 309                                                    exi,
 310                                                    special ? special :
 311                                                    lptr->defn.special);
 312             }
 313         }
 314     }                           /* if (pass0 == 1) */
 315 }
 316
 317 void define_common(char *label, int32_t segment, int32_t size, char *special,
 318                    struct ofmt *ofmt, efunc error)
 319 {
 320     union label *lptr;
 321
 322     lptr = find_label(label, 1);
 323     if (lptr->defn.is_global & DEFINED_BIT) {
 324         error(ERR_NONFATAL, "symbol `%s' redefined", label);
 325         return;
 326     }
 327     lptr->defn.is_global |= DEFINED_BIT;
 328
 329     if (!islocalchar(label[0])) /* not local, but not special either */
 330         prevlabel = lptr->defn.label;
 331     else
 332         error(ERR_NONFATAL, "attempt to define a local label as a "
 333               "common variable");
 334
 335     lptr->defn.segment = segment;
 336     lptr->defn.offset = 0;
 337
 338     ofmt->symdef(lptr->defn.label, segment, size, 2,
 339                  special ? special : lptr->defn.special);
 340     ofmt->current_dfmt->debug_deflabel(lptr->defn.label, segment, size, 2,
 341                                        special ? special : lptr->defn.
 342                                        special);
 343 }
 344
 345 void declare_as_global(char *label, char *special, efunc error)
 346 {
 347     union label *lptr;
 348
 349     if (islocal(label)) {
 350         error(ERR_NONFATAL, "attempt to declare local symbol `%s' as"
 351               " global", label);
 352         return;
 353     }
 354     lptr = find_label(label, 1);
 355     switch (lptr->defn.is_global & TYPE_MASK) {
 356     case NOT_DEFINED_YET:
 357         lptr->defn.is_global = GLOBAL_PLACEHOLDER;
 358         lptr->defn.special = special ? perm_copy(special) : NULL;
 359         break;
 360     case GLOBAL_PLACEHOLDER:   /* already done: silently ignore */
 361     case GLOBAL_SYMBOL:
 362         break;
 363     case LOCAL_SYMBOL:
 364         if (!lptr->defn.is_global & EXTERN_BIT)
 365             error(ERR_NONFATAL, "symbol `%s': GLOBAL directive must"
 366                   " appear before symbol definition", label);
 367         break;
 368     }
 369 }
 370
 371 int init_labels(void)
 372 {
 373     ltab = hash_init();
 374
 375     ldata = lfree = (union label *)nasm_malloc(LBLK_SIZE);
 376     init_block(lfree);
 377
 378     perm_head =
 379         perm_tail = (struct permts *)nasm_malloc(sizeof(struct permts));
 380
 381     perm_head->next = NULL;
 382     perm_head->size = PERMTS_SIZE;
 383     perm_head->usage = 0;
 384
 385     prevlabel = "";
 386
 387     initialized = TRUE;
 388
 389     return 0;
 390 }
 391
 392 void cleanup_labels(void)
 393 {
 394     union label *lptr, *lhold;
 395
 396     initialized = FALSE;
 397
 398     hash_free(ltab);
 399
 400     lptr = lhold = ldata;
 401     while (lptr) {
 402         lptr = &lptr[LABEL_BLOCK-1];
 403         lptr = lptr->admin.next;
 404         nasm_free(lhold);
 405         lhold = lptr;
 406     }
 407
 408     while (perm_head) {
 409         perm_tail = perm_head;
 410         perm_head = perm_head->next;
 411         nasm_free(perm_tail);
 412     }
 413 }
 414
 415 static void init_block(union label *blk)
 416 {
 417     int j;
 418
 419     for (j = 0; j < LABEL_BLOCK - 1; j++)
 420         blk[j].admin.movingon = END_LIST;
 421     blk[LABEL_BLOCK - 1].admin.movingon = END_BLOCK;
 422     blk[LABEL_BLOCK - 1].admin.next = NULL;
 423 }
 424
 425 static char *perm_copy(const char *string)
 426 {
 427     char *p;
 428     int len = strlen(string)+1;
 429
 430     if (perm_tail->size - perm_tail->usage < len) {
 431         perm_tail->next =
 432             (struct permts *)nasm_malloc(sizeof(struct permts));
 433         perm_tail = perm_tail->next;
 434         perm_tail->next = NULL;
 435         perm_tail->size = PERMTS_SIZE;
 436         perm_tail->usage = 0;
 437     }
 438     p = perm_tail->data + perm_tail->usage;
 439     memcpy(p, string, len);
 440     perm_tail->usage += len;
 441
 442     return p;
 443 }
 444
 445 /*
 446  * Notes regarding bug involving redefinition of external segments.
 447  *
 448  * Up to and including v0.97, the following code didn't work. From 0.97
 449  * developers release 2 onwards, it will generate an error.
 450  *
 451  * EXTERN extlabel
 452  * newlabel EQU extlabel + 1
 453  *
 454  * The results of allowing this code through are that two import records
 455  * are generated, one for 'extlabel' and one for 'newlabel'.
 456  *
 457  * The reason for this is an inadequacy in the defined interface between
 458  * the label manager and the output formats. The problem lies in how the
 459  * output format driver tells that a label is an external label for which
 460  * a label import record must be produced. Most (all except bin?) produce
 461  * the record if the segment number of the label is not one of the internal
 462  * segments that the output driver is producing.
 463  *
 464  * A simple fix to this would be to make the output formats keep track of
 465  * which symbols they've produced import records for, and make them not
 466  * produce import records for segments that are already defined.
 467  *
 468  * The best way, which is slightly harder but reduces duplication of code
 469  * and should therefore make the entire system smaller and more stable is
 470  * to change the interface between assembler, define_label(), and
 471  * the output module. The changes that are needed are:
 472  *
 473  * The semantics of the 'isextern' flag passed to define_label() need
 474  * examining. This information may or may not tell us what we need to
 475  * know (ie should we be generating an import record at this point for this
 476  * label). If these aren't the semantics, the semantics should be changed
 477  * to this.
 478  *
 479  * The output module interface needs changing, so that the `isextern' flag
 480  * is passed to the module, so that it can be easily tested for.
 481  */