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