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 NOT_DEFINED_YET 0
  33 #define LOCAL_SYMBOL 1
  34 #define GLOBAL_SYMBOL 2
  35 #define GLOBAL_PLACEHOLDER 3
  36
  37 union label {                          /* actual label structures */
  38     struct {
  39         long segment, offset;
  40         char *label;
  41         int is_global;
  42     } defn;
  43     struct {
  44         long movingon, dummy;
  45         union label *next;
  46     } admin;
  47 };
  48
  49 struct permts {                        /* permanent text storage */
  50     struct permts *next;               /* for the linked list */
  51     int size, usage;                   /* size and used space in ... */
  52     char data[PERMTS_SIZE];            /* ... the data block itself */
  53 };
  54
  55 static union label *ltab[LABEL_HASHES];/* using a hash table */
  56 static union label *lfree[LABEL_HASHES];/* pointer into the above */
  57 static struct permts *perm_head;      /* start of perm. text storage */
  58 static struct permts *perm_tail;      /* end of perm. text storage */
  59
  60 static void init_block (union label *blk);
  61 static char *perm_copy (char *string1, char *string2);
  62
  63 static char *prevlabel;
  64
  65 /*
  66  * Internal routine: finds the `union label' corresponding to the
  67  * given label name. Creates a new one, if it isn't found, and if
  68  * `create' is TRUE.
  69  */
  70 static union label *find_label (char *label, int create) {
  71     int hash = 0;
  72     char *p, *prev;
  73     int prevlen;
  74     union label *lptr;
  75
  76     if (islocal(label))
  77         prev = prevlabel;
  78     else
  79         prev = "";
  80     prevlen = strlen(prev);
  81     p = prev;
  82     while (*p) hash += *p++;
  83     p = label;
  84     while (*p) hash += *p++;
  85     hash %= LABEL_HASHES;
  86     lptr = ltab[hash];
  87     while (lptr->admin.movingon != END_LIST) {
  88         if (lptr->admin.movingon == END_BLOCK) {
  89             lptr = lptr->admin.next;
  90         }
  91         if (!strncmp(lptr->defn.label, prev, prevlen) &&
  92             !strcmp(lptr->defn.label+prevlen, label))
  93             return lptr;
  94         lptr++;
  95     }
  96     if (create) {
  97         if (lfree[hash]->admin.movingon == END_BLOCK) {
  98             /*
  99              * must allocate a new block
 100              */
 101             lfree[hash]->admin.next = (union label *) nasm_malloc (LBLK_SIZE);
 102             lfree[hash] = lfree[hash]->admin.next;
 103             init_block(lfree[hash]);
 104         }
 105
 106         lfree[hash]->admin.movingon = BOGUS_VALUE;
 107         lfree[hash]->defn.label = perm_copy (prev, label);
 108         lfree[hash]->defn.is_global = NOT_DEFINED_YET;
 109         return lfree[hash]++;
 110     } else
 111         return NULL;
 112 }
 113
 114 int lookup_label (char *label, long *segment, long *offset) {
 115     union label *lptr;
 116
 117     lptr = find_label (label, 0);
 118     if (lptr && (lptr->defn.is_global == LOCAL_SYMBOL ||
 119                  lptr->defn.is_global == GLOBAL_SYMBOL)) {
 120         *segment = lptr->defn.segment;
 121         *offset = lptr->defn.offset;
 122         return 1;
 123     } else
 124         return 0;
 125 }
 126
 127 void define_label_stub (char *label, efunc error) {
 128     union label *lptr;
 129
 130     if (!islocal(label)) {
 131         lptr = find_label (label, 1);
 132         if (!lptr)
 133             error (ERR_PANIC, "can't find label `%s' on pass two", label);
 134         prevlabel = lptr->defn.label;
 135     }
 136 }
 137
 138 void define_label (char *label, long segment, long offset,
 139                    struct ofmt *ofmt, efunc error) {
 140     union label *lptr;
 141
 142     lptr = find_label (label, 1);
 143     switch (lptr->defn.is_global) {
 144       case NOT_DEFINED_YET:
 145         lptr->defn.is_global = LOCAL_SYMBOL;
 146         break;
 147       case GLOBAL_PLACEHOLDER:
 148         lptr->defn.is_global = GLOBAL_SYMBOL;
 149         break;
 150       default:
 151         error(ERR_NONFATAL, "symbol `%s' redefined", label);
 152         return;
 153     }
 154
 155     if (label[0] != '.')               /* not local, but not special either */
 156         prevlabel = lptr->defn.label;
 157     else if (!*prevlabel)
 158         error(ERR_NONFATAL, "attempt to define a local label before any"
 159               " non-local labels");
 160
 161     lptr->defn.segment = segment;
 162     lptr->defn.offset = offset;
 163
 164     ofmt->symdef (lptr->defn.label, segment, offset,
 165                   lptr->defn.is_global == GLOBAL_SYMBOL);
 166 }
 167
 168 void define_common (char *label, long segment, long size,
 169                     struct ofmt *ofmt, efunc error) {
 170     union label *lptr;
 171
 172     lptr = find_label (label, 1);
 173     switch (lptr->defn.is_global) {
 174       case NOT_DEFINED_YET:
 175         lptr->defn.is_global = LOCAL_SYMBOL;
 176         break;
 177       case GLOBAL_PLACEHOLDER:
 178         lptr->defn.is_global = GLOBAL_SYMBOL;
 179         break;
 180       default:
 181         error(ERR_NONFATAL, "symbol `%s' redefined", label);
 182         return;
 183     }
 184
 185     if (label[0] != '.')               /* not local, but not special either */
 186         prevlabel = lptr->defn.label;
 187     else
 188         error(ERR_NONFATAL, "attempt to define a local label as a "
 189               "common variable");
 190
 191     lptr->defn.segment = segment;
 192     lptr->defn.offset = 0;
 193
 194     ofmt->symdef (lptr->defn.label, segment, size, 2);
 195 }
 196
 197 void declare_as_global (char *label, efunc error) {
 198     union label *lptr;
 199
 200     if (islocal(label)) {
 201         error(ERR_NONFATAL, "attempt to declare local symbol `%s' as"
 202               " global", label);
 203         return;
 204     }
 205     lptr = find_label (label, 1);
 206     switch (lptr->defn.is_global) {
 207       case NOT_DEFINED_YET:
 208         lptr->defn.is_global = GLOBAL_PLACEHOLDER;
 209         break;
 210       case GLOBAL_PLACEHOLDER:         /* already done: silently ignore */
 211       case GLOBAL_SYMBOL:
 212         break;
 213       case LOCAL_SYMBOL:
 214         error(ERR_NONFATAL, "symbol `%s': [GLOBAL] directive must"
 215               " appear before symbol definition", label);
 216         break;
 217     }
 218 }
 219
 220 int init_labels (void) {
 221     int i;
 222
 223     for (i=0; i<LABEL_HASHES; i++) {
 224         ltab[i] = (union label *) nasm_malloc (LBLK_SIZE);
 225         if (!ltab[i])
 226             return -1;                 /* can't initialise, panic */
 227         init_block (ltab[i]);
 228         lfree[i] = ltab[i];
 229     }
 230
 231     perm_head = perm_tail = (struct permts *) nasm_malloc (sizeof(struct permts));
 232     if (!perm_head)
 233         return -1;
 234
 235     perm_head->next = NULL;
 236     perm_head->size = PERMTS_SIZE;
 237     perm_head->usage = 0;
 238
 239     prevlabel = "";
 240
 241     return 0;
 242 }
 243
 244 void cleanup_labels (void) {
 245     int i;
 246
 247     for (i=0; i<LABEL_HASHES; i++) {
 248         union label *lptr, *lhold;
 249
 250         lptr = lhold = ltab[i];
 251
 252         while (lptr) {
 253             while (lptr->admin.movingon != END_BLOCK) lptr++;
 254             lptr = lptr->admin.next;
 255             nasm_free (lhold);
 256             lhold = lptr;
 257         }
 258     }
 259
 260     while (perm_head) {
 261         perm_tail = perm_head;
 262         perm_head = perm_head->next;
 263         nasm_free (perm_tail);
 264     }
 265 }
 266
 267 static void init_block (union label *blk) {
 268     int j;
 269
 270     for (j=0; j<LABEL_BLOCK-1; j++)
 271         blk[j].admin.movingon = END_LIST;
 272     blk[LABEL_BLOCK-1].admin.movingon = END_BLOCK;
 273     blk[LABEL_BLOCK-1].admin.next = NULL;
 274 }
 275
 276 static char *perm_copy (char *string1, char *string2) {
 277     char *p, *q;
 278     int len = strlen(string1)+strlen(string2)+1;
 279
 280     if (perm_tail->size - perm_tail->usage < len) {
 281         perm_tail->next = (struct permts *)nasm_malloc(sizeof(struct permts));
 282         perm_tail = perm_tail->next;
 283         perm_tail->size = PERMTS_SIZE;
 284         perm_tail->usage = 0;
 285     }
 286     p = q = perm_tail->data + perm_tail->usage;
 287     while ( (*q = *string1++) ) q++;
 288     while ( (*q++ = *string2++) );
 289     perm_tail->usage = q - perm_tail->data;
 290
 291     return p;
 292 }