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 license given in the file "LICENSE"
   6  * distributed in the NASM archive.
   7  */
   8
   9 #include "compiler.h"
  10
  11 #include <stdio.h>
  12 #include <string.h>
  13 #include <stdlib.h>
  14 #include <inttypes.h>
  15
  16 #include "nasm.h"
  17 #include "nasmlib.h"
  18 #include "hashtbl.h"
  19
  20 /*
  21  * A local label is one that begins with exactly one period. Things
  22  * that begin with _two_ periods are NASM-specific things.
  23  *
  24  * If TASM compatibility is enabled, a local label can also begin with
  25  * @@, so @@local is a TASM compatible local label. Note that we only
  26  * check for the first @ symbol, although TASM requires both.
  27  */
  28 #define islocal(l)                                              \
  29         (tasm_compatible_mode ?                                 \
  30         (((l)[0] == '.' || (l)[0] == '@') && (l)[1] != '.') :   \
  31         ((l)[0] == '.' && (l)[1] != '.'))
  32 #define islocalchar(c)                                          \
  33         (tasm_compatible_mode ?                                  \
  34         ((c) == '.' || (c) == '@') :                            \
  35         ((c) == '.'))
  36
  37 #define LABEL_BLOCK  128        /* no. of labels/block */
  38 #define LBLK_SIZE    (LABEL_BLOCK*sizeof(union label))
  39
  40 #define END_LIST -3             /* don't clash with NO_SEG! */
  41 #define END_BLOCK -2
  42 #define BOGUS_VALUE -4
  43
  44 #define PERMTS_SIZE  4096       /* size of text blocks */
  45 #if (PERMTS_SIZE > IDLEN_MAX)
  46 #error "IPERMTS_SIZE must be less than or equal to IDLEN_MAX"
  47 #endif
  48
  49 /* values for label.defn.is_global */
  50 #define DEFINED_BIT 1
  51 #define GLOBAL_BIT 2
  52 #define EXTERN_BIT 4
  53
  54 #define NOT_DEFINED_YET 0
  55 #define TYPE_MASK 3
  56 #define LOCAL_SYMBOL (DEFINED_BIT)
  57 #define GLOBAL_PLACEHOLDER (GLOBAL_BIT)
  58 #define GLOBAL_SYMBOL (DEFINED_BIT|GLOBAL_BIT)
  59
  60 union label {                   /* actual label structures */
  61     struct {
  62         int32_t segment;
  63         int64_t offset;
  64         char *label, *special;
  65         int is_global, is_norm;
  66     } defn;
  67     struct {
  68         int32_t movingon;
  69         int64_t dummy;
  70         union label *next;
  71     } admin;
  72 };
  73
  74 struct permts {                 /* permanent text storage */
  75     struct permts *next;        /* for the linked list */
  76     int size, usage;            /* size and used space in ... */
  77     char data[PERMTS_SIZE];     /* ... the data block itself */
  78 };
  79
  80 extern int64_t global_offset_changed;       /* defined in nasm.c */
  81
  82 static struct hash_table ltab;          /* labels hash table */
  83 static union label *ldata;              /* all label data blocks */
  84 static union label *lfree;              /* labels free block */
  85 static struct permts *perm_head;        /* start of perm. text storage */
  86 static struct permts *perm_tail;        /* end of perm. text storage */
  87
  88 static void init_block(union label *blk);
  89 static char *perm_copy(const char *string);
  90
  91 static char *prevlabel;
  92
  93 static bool initialized = false;
  94
  95 char lprefix[PREFIX_MAX] = { 0 };
  96 char lpostfix[PREFIX_MAX] = { 0 };
  97
  98 /*
  99  * Internal routine: finds the `union label' corresponding to the
 100  * given label name. Creates a new one, if it isn't found, and if
 101  * `create' is true.
 102  */
 103 static union label *find_label(char *label, int create)
 104 {
 105     char *prev;
 106     int prevlen, len;
 107     union label *lptr, **lpp;
 108     char label_str[IDLEN_MAX];
 109     struct hash_insert ip;
 110
 111     if (islocal(label)) {
 112         prev = prevlabel;
 113         prevlen = strlen(prev);
 114         len = strlen(label);
 115         if (prevlen+len >= IDLEN_MAX)
 116             return NULL;        /* Error... */
 117         memcpy(label_str, prev, prevlen);
 118         memcpy(label_str+prevlen, label, len+1);
 119         label = label_str;
 120     } else {
 121         prev = "";
 122         prevlen = 0;
 123     }
 124
 125     lpp = (union label **) hash_find(&ltab, label, &ip);
 126     lptr = lpp ? *lpp : NULL;
 127
 128     if (lptr || !create)
 129         return lptr;
 130
 131     /* Create a new label... */
 132     if (lfree->admin.movingon == END_BLOCK) {
 133         /*
 134          * must allocate a new block
 135          */
 136         lfree->admin.next =
 137             (union label *)nasm_malloc(LBLK_SIZE);
 138         lfree = lfree->admin.next;
 139         init_block(lfree);
 140     }
 141
 142     lfree->admin.movingon = BOGUS_VALUE;
 143     lfree->defn.label = perm_copy(label);
 144     lfree->defn.special = NULL;
 145     lfree->defn.is_global = NOT_DEFINED_YET;
 146
 147     hash_add(&ip, lfree->defn.label, lfree);
 148     return lfree++;
 149 }
 150
 151 bool lookup_label(char *label, int32_t *segment, int64_t *offset)
 152 {
 153     union label *lptr;
 154
 155     if (!initialized)
 156         return false;
 157
 158     lptr = find_label(label, 0);
 159     if (lptr && (lptr->defn.is_global & DEFINED_BIT)) {
 160         *segment = lptr->defn.segment;
 161         *offset = lptr->defn.offset;
 162         return true;
 163     } else
 164         return false;
 165 }
 166
 167 bool is_extern(char *label)
 168 {
 169     union label *lptr;
 170
 171     if (!initialized)
 172         return false;
 173
 174     lptr = find_label(label, 0);
 175     return (lptr && (lptr->defn.is_global & EXTERN_BIT));
 176 }
 177
 178 void redefine_label(char *label, int32_t segment, int64_t offset, char *special,
 179                     bool is_norm, bool isextrn, struct ofmt *ofmt,
 180                     efunc error)
 181 {
 182     union label *lptr;
 183     int exi;
 184
 185     /* This routine possibly ought to check for phase errors.  Most assemblers
 186      * check for phase errors at this point.  I don't know whether phase errors
 187      * are even possible, nor whether they are checked somewhere else
 188      */
 189
 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     if (lptr->defn.offset != offset) global_offset_changed++;
 213     lptr->defn.offset = offset;
 214     lptr->defn.segment = segment;
 215
 216     if (pass0 == 1) {
 217         exi = !!(lptr->defn.is_global & GLOBAL_BIT);
 218         if (exi) {
 219             char *xsymbol;
 220             int slen;
 221             slen = strlen(lprefix);
 222             slen += strlen(lptr->defn.label);
 223             slen += strlen(lpostfix);
 224             slen++;             /* room for that null char */
 225             xsymbol = nasm_malloc(slen);
 226             snprintf(xsymbol, slen, "%s%s%s", lprefix, lptr->defn.label,
 227                      lpostfix);
 228
 229             ofmt->symdef(xsymbol, segment, offset, exi,
 230                          special ? special : lptr->defn.special);
 231             ofmt->current_dfmt->debug_deflabel(xsymbol, segment, offset,
 232                                                exi,
 233                                                special ? special : lptr->
 234                                                defn.special);
 235 /**     nasm_free(xsymbol);  ! outobj.c stores the pointer; ouch!!! **/
 236         } else {
 237             if ((lptr->defn.is_global & (GLOBAL_BIT | EXTERN_BIT)) !=
 238                 EXTERN_BIT) {
 239                 ofmt->symdef(lptr->defn.label, segment, offset, exi,
 240                              special ? special : lptr->defn.special);
 241                 ofmt->current_dfmt->debug_deflabel(label, segment, offset,
 242                                                    exi,
 243                                                    special ? special :
 244                                                    lptr->defn.special);
 245             }
 246         }
 247     }
 248     /* if (pass0 == 1) */
 249 }
 250
 251 void define_label(char *label, int32_t segment, int64_t offset, char *special,
 252                   bool is_norm, bool isextrn, struct ofmt *ofmt, efunc error)
 253 {
 254     union label *lptr;
 255     int exi;
 256
 257 #ifdef DEBUG
 258 #if DEBUG<3
 259     if (!strncmp(label, "debugdump", 9))
 260 #endif
 261         error(ERR_DEBUG, "define_label (%s, %ld, %08lx, %s, %d, %d)",
 262               label, segment, offset, special, is_norm, isextrn);
 263 #endif
 264     lptr = find_label(label, 1);
 265     if (lptr->defn.is_global & DEFINED_BIT) {
 266         error(ERR_NONFATAL, "symbol `%s' redefined", label);
 267         return;
 268     }
 269     lptr->defn.is_global |= DEFINED_BIT;
 270     if (isextrn)
 271         lptr->defn.is_global |= EXTERN_BIT;
 272
 273     if (!islocalchar(label[0]) && is_norm)      /* not local, but not special either */
 274         prevlabel = lptr->defn.label;
 275     else if (islocal(label) && !*prevlabel) {
 276         error(ERR_NONFATAL, "attempt to define a local label before any"
 277               " non-local labels");
 278     }
 279
 280     lptr->defn.segment = segment;
 281     lptr->defn.offset = offset;
 282     lptr->defn.is_norm = (!islocalchar(label[0]) && is_norm);
 283
 284     if (pass0 == 1 || (!is_norm && !isextrn && (segment > 0) && (segment & 1))) {
 285         exi = !!(lptr->defn.is_global & GLOBAL_BIT);
 286         if (exi) {
 287             char *xsymbol;
 288             int slen;
 289             slen = strlen(lprefix);
 290             slen += strlen(lptr->defn.label);
 291             slen += strlen(lpostfix);
 292             slen++;             /* room for that null char */
 293             xsymbol = nasm_malloc(slen);
 294             snprintf(xsymbol, slen, "%s%s%s", lprefix, lptr->defn.label,
 295                      lpostfix);
 296
 297             ofmt->symdef(xsymbol, segment, offset, exi,
 298                          special ? special : lptr->defn.special);
 299             ofmt->current_dfmt->debug_deflabel(xsymbol, segment, offset,
 300                                                exi,
 301                                                special ? special : lptr->
 302                                                defn.special);
 303 /**     nasm_free(xsymbol);  ! outobj.c stores the pointer; ouch!!! **/
 304         } else {
 305             if ((lptr->defn.is_global & (GLOBAL_BIT | EXTERN_BIT)) !=
 306                 EXTERN_BIT) {
 307                 ofmt->symdef(lptr->defn.label, segment, offset, exi,
 308                              special ? special : lptr->defn.special);
 309                 ofmt->current_dfmt->debug_deflabel(label, segment, offset,
 310                                                    exi,
 311                                                    special ? special :
 312                                                    lptr->defn.special);
 313             }
 314         }
 315     }                           /* if (pass0 == 1) */
 316 }
 317
 318 void define_common(char *label, int32_t segment, int32_t size, char *special,
 319                    struct ofmt *ofmt, efunc error)
 320 {
 321     union label *lptr;
 322
 323     lptr = find_label(label, 1);
 324     if (lptr->defn.is_global & DEFINED_BIT) {
 325         error(ERR_NONFATAL, "symbol `%s' redefined", label);
 326         return;
 327     }
 328     lptr->defn.is_global |= DEFINED_BIT;
 329
 330     if (!islocalchar(label[0])) /* not local, but not special either */
 331         prevlabel = lptr->defn.label;
 332     else
 333         error(ERR_NONFATAL, "attempt to define a local label as a "
 334               "common variable");
 335
 336     lptr->defn.segment = segment;
 337     lptr->defn.offset = 0;
 338
 339     ofmt->symdef(lptr->defn.label, segment, size, 2,
 340                  special ? special : lptr->defn.special);
 341     ofmt->current_dfmt->debug_deflabel(lptr->defn.label, segment, size, 2,
 342                                        special ? special : lptr->defn.
 343                                        special);
 344 }
 345
 346 void declare_as_global(char *label, char *special, efunc error)
 347 {
 348     union label *lptr;
 349
 350     if (islocal(label)) {
 351         error(ERR_NONFATAL, "attempt to declare local symbol `%s' as"
 352               " global", label);
 353         return;
 354     }
 355     lptr = find_label(label, 1);
 356     switch (lptr->defn.is_global & TYPE_MASK) {
 357     case NOT_DEFINED_YET:
 358         lptr->defn.is_global = GLOBAL_PLACEHOLDER;
 359         lptr->defn.special = special ? perm_copy(special) : NULL;
 360         break;
 361     case GLOBAL_PLACEHOLDER:   /* already done: silently ignore */
 362     case GLOBAL_SYMBOL:
 363         break;
 364     case LOCAL_SYMBOL:
 365         if (!lptr->defn.is_global & EXTERN_BIT)
 366             error(ERR_NONFATAL, "symbol `%s': GLOBAL directive must"
 367                   " appear before symbol definition", label);
 368         break;
 369     }
 370 }
 371
 372 int init_labels(void)
 373 {
 374     hash_init(&ltab, HASH_LARGE);
 375
 376     ldata = lfree = (union label *)nasm_malloc(LBLK_SIZE);
 377     init_block(lfree);
 378
 379     perm_head =
 380         perm_tail = (struct permts *)nasm_malloc(sizeof(struct permts));
 381
 382     perm_head->next = NULL;
 383     perm_head->size = PERMTS_SIZE;
 384     perm_head->usage = 0;
 385
 386     prevlabel = "";
 387
 388     initialized = true;
 389
 390     return 0;
 391 }
 392
 393 void cleanup_labels(void)
 394 {
 395     union label *lptr, *lhold;
 396
 397     initialized = false;
 398
 399     hash_free(&ltab);
 400
 401     lptr = lhold = ldata;
 402     while (lptr) {
 403         lptr = &lptr[LABEL_BLOCK-1];
 404         lptr = lptr->admin.next;
 405         nasm_free(lhold);
 406         lhold = lptr;
 407     }
 408
 409     while (perm_head) {
 410         perm_tail = perm_head;
 411         perm_head = perm_head->next;
 412         nasm_free(perm_tail);
 413     }
 414 }
 415
 416 static void init_block(union label *blk)
 417 {
 418     int j;
 419
 420     for (j = 0; j < LABEL_BLOCK - 1; j++)
 421         blk[j].admin.movingon = END_LIST;
 422     blk[LABEL_BLOCK - 1].admin.movingon = END_BLOCK;
 423     blk[LABEL_BLOCK - 1].admin.next = NULL;
 424 }
 425
 426 static char *perm_copy(const char *string)
 427 {
 428     char *p;
 429     int len = strlen(string)+1;
 430
 431     if (perm_tail->size - perm_tail->usage < len) {
 432         perm_tail->next =
 433             (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 = perm_tail->data + perm_tail->usage;
 440     memcpy(p, string, len);
 441     perm_tail->usage += len;
 442
 443     return p;
 444 }
 445
 446 char *local_scope(char *label)
 447 {
 448    return islocal(label) ? prevlabel : "";
 449 }
 450
 451 /*
 452  * Notes regarding bug involving redefinition of external segments.
 453  *
 454  * Up to and including v0.97, the following code didn't work. From 0.97
 455  * developers release 2 onwards, it will generate an error.
 456  *
 457  * EXTERN extlabel
 458  * newlabel EQU extlabel + 1
 459  *
 460  * The results of allowing this code through are that two import records
 461  * are generated, one for 'extlabel' and one for 'newlabel'.
 462  *
 463  * The reason for this is an inadequacy in the defined interface between
 464  * the label manager and the output formats. The problem lies in how the
 465  * output format driver tells that a label is an external label for which
 466  * a label import record must be produced. Most (all except bin?) produce
 467  * the record if the segment number of the label is not one of the internal
 468  * segments that the output driver is producing.
 469  *
 470  * A simple fix to this would be to make the output formats keep track of
 471  * which symbols they've produced import records for, and make them not
 472  * produce import records for segments that are already defined.
 473  *
 474  * The best way, which is slightly harder but reduces duplication of code
 475  * and should therefore make the entire system smaller and more stable is
 476  * to change the interface between assembler, define_label(), and
 477  * the output module. The changes that are needed are:
 478  *
 479  * The semantics of the 'isextern' flag passed to define_label() need
 480  * examining. This information may or may not tell us what we need to
 481  * know (ie should we be generating an import record at this point for this
 482  * label). If these aren't the semantics, the semantics should be changed
 483  * to this.
 484  *
 485  * The output module interface needs changing, so that the `isextern' flag
 486  * is passed to the module, so that it can be easily tested for.
 487  */