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