2009-12-02 Rafael Avila de Espindola <espindola@google.com>
[binutils.git] / bfd / stabs.c
blob8a1cd87e068f93912c0720db170440503a189192
1 /* Stabs in sections linking support.
2 Copyright 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
3 2006, 2007, 2008 Free Software Foundation, Inc.
4 Written by Ian Lance Taylor, Cygnus Support.
6 This file is part of BFD, the Binary File Descriptor library.
8 This program is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 3 of the License, or
11 (at your option) any later version.
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with this program; if not, write to the Free Software
20 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21 MA 02110-1301, USA. */
24 /* This file contains support for linking stabs in sections, as used
25 on COFF and ELF. */
27 #include "sysdep.h"
28 #include "bfd.h"
29 #include "libbfd.h"
30 #include "aout/stab_gnu.h"
31 #include "safe-ctype.h"
33 /* Stabs entries use a 12 byte format:
34 4 byte string table index
35 1 byte stab type
36 1 byte stab other field
37 2 byte stab desc field
38 4 byte stab value
39 FIXME: This will have to change for a 64 bit object format.
41 The stabs symbols are divided into compilation units. For the
42 first entry in each unit, the type of 0, the value is the length of
43 the string table for this unit, and the desc field is the number of
44 stabs symbols for this unit. */
46 #define STRDXOFF 0
47 #define TYPEOFF 4
48 #define OTHEROFF 5
49 #define DESCOFF 6
50 #define VALOFF 8
51 #define STABSIZE 12
53 /* A linked list of totals that we have found for a particular header
54 file. A total is a unique identifier for a particular BINCL...EINCL
55 sequence of STABs that can be used to identify duplicate sequences.
56 It consists of three fields, 'sum_chars' which is the sum of all the
57 STABS characters; 'num_chars' which is the number of these charactes
58 and 'symb' which is a buffer of all the symbols in the sequence. This
59 buffer is only checked as a last resort. */
61 struct stab_link_includes_totals
63 struct stab_link_includes_totals *next;
64 bfd_vma sum_chars; /* Accumulated sum of STABS characters. */
65 bfd_vma num_chars; /* Number of STABS characters. */
66 const char* symb; /* The STABS characters themselves. */
69 /* An entry in the header file hash table. */
71 struct stab_link_includes_entry
73 struct bfd_hash_entry root;
74 /* List of totals we have found for this file. */
75 struct stab_link_includes_totals *totals;
78 /* This structure is used to hold a list of N_BINCL symbols, some of
79 which might be converted into N_EXCL symbols. */
81 struct stab_excl_list
83 /* The next symbol to convert. */
84 struct stab_excl_list *next;
85 /* The offset to this symbol in the section contents. */
86 bfd_size_type offset;
87 /* The value to use for the symbol. */
88 bfd_vma val;
89 /* The type of this symbol (N_BINCL or N_EXCL). */
90 int type;
93 /* This structure is stored with each .stab section. */
95 struct stab_section_info
97 /* This is a linked list of N_BINCL symbols which should be
98 converted into N_EXCL symbols. */
99 struct stab_excl_list *excls;
101 /* This is used to map input stab offsets within their sections
102 to output stab offsets, to take into account stabs that have
103 been deleted. If it is NULL, the output offsets are the same
104 as the input offsets, because no stabs have been deleted from
105 this section. Otherwise the i'th entry is the number of
106 bytes of stabs that have been deleted prior to the i'th
107 stab. */
108 bfd_size_type *cumulative_skips;
110 /* This is an array of string indices. For each stab symbol, we
111 store the string index here. If a stab symbol should not be
112 included in the final output, the string index is -1. */
113 bfd_size_type stridxs[1];
117 /* The function to create a new entry in the header file hash table. */
119 static struct bfd_hash_entry *
120 stab_link_includes_newfunc (struct bfd_hash_entry *entry,
121 struct bfd_hash_table *table,
122 const char *string)
124 struct stab_link_includes_entry *ret =
125 (struct stab_link_includes_entry *) entry;
127 /* Allocate the structure if it has not already been allocated by a
128 subclass. */
129 if (ret == NULL)
130 ret = (struct stab_link_includes_entry *)
131 bfd_hash_allocate (table, sizeof (struct stab_link_includes_entry));
132 if (ret == NULL)
133 return NULL;
135 /* Call the allocation method of the superclass. */
136 ret = ((struct stab_link_includes_entry *)
137 bfd_hash_newfunc ((struct bfd_hash_entry *) ret, table, string));
138 if (ret)
139 /* Set local fields. */
140 ret->totals = NULL;
142 return (struct bfd_hash_entry *) ret;
145 /* This function is called for each input file from the add_symbols
146 pass of the linker. */
148 bfd_boolean
149 _bfd_link_section_stabs (bfd *abfd,
150 struct stab_info *sinfo,
151 asection *stabsec,
152 asection *stabstrsec,
153 void * *psecinfo,
154 bfd_size_type *pstring_offset)
156 bfd_boolean first;
157 bfd_size_type count, amt;
158 struct stab_section_info *secinfo;
159 bfd_byte *stabbuf = NULL;
160 bfd_byte *stabstrbuf = NULL;
161 bfd_byte *sym, *symend;
162 bfd_size_type stroff, next_stroff, skip;
163 bfd_size_type *pstridx;
165 if (stabsec->size == 0
166 || stabstrsec->size == 0)
167 /* This file does not contain stabs debugging information. */
168 return TRUE;
170 if (stabsec->size % STABSIZE != 0)
171 /* Something is wrong with the format of these stab symbols.
172 Don't try to optimize them. */
173 return TRUE;
175 if ((stabstrsec->flags & SEC_RELOC) != 0)
176 /* We shouldn't see relocations in the strings, and we aren't
177 prepared to handle them. */
178 return TRUE;
180 if (bfd_is_abs_section (stabsec->output_section)
181 || bfd_is_abs_section (stabstrsec->output_section))
182 /* At least one of the sections is being discarded from the
183 link, so we should just ignore them. */
184 return TRUE;
186 first = FALSE;
188 if (sinfo->stabstr == NULL)
190 flagword flags;
192 /* Initialize the stabs information we need to keep track of. */
193 first = TRUE;
194 sinfo->strings = _bfd_stringtab_init ();
195 if (sinfo->strings == NULL)
196 goto error_return;
197 /* Make sure the first byte is zero. */
198 (void) _bfd_stringtab_add (sinfo->strings, "", TRUE, TRUE);
199 if (! bfd_hash_table_init (&sinfo->includes,
200 stab_link_includes_newfunc,
201 sizeof (struct stab_link_includes_entry)))
202 goto error_return;
203 flags = (SEC_HAS_CONTENTS | SEC_READONLY | SEC_DEBUGGING
204 | SEC_LINKER_CREATED);
205 sinfo->stabstr = bfd_make_section_anyway_with_flags (abfd, ".stabstr",
206 flags);
207 if (sinfo->stabstr == NULL)
208 goto error_return;
211 /* Initialize the information we are going to store for this .stab
212 section. */
213 count = stabsec->size / STABSIZE;
215 amt = sizeof (struct stab_section_info);
216 amt += (count - 1) * sizeof (bfd_size_type);
217 *psecinfo = bfd_alloc (abfd, amt);
218 if (*psecinfo == NULL)
219 goto error_return;
221 secinfo = (struct stab_section_info *) *psecinfo;
222 secinfo->excls = NULL;
223 stabsec->rawsize = stabsec->size;
224 secinfo->cumulative_skips = NULL;
225 memset (secinfo->stridxs, 0, (size_t) count * sizeof (bfd_size_type));
227 /* Read the stabs information from abfd. */
228 if (!bfd_malloc_and_get_section (abfd, stabsec, &stabbuf)
229 || !bfd_malloc_and_get_section (abfd, stabstrsec, &stabstrbuf))
230 goto error_return;
232 /* Look through the stabs symbols, work out the new string indices,
233 and identify N_BINCL symbols which can be eliminated. */
234 stroff = 0;
235 /* The stabs sections can be split when
236 -split-by-reloc/-split-by-file is used. We must keep track of
237 each stab section's place in the single concatenated string
238 table. */
239 next_stroff = pstring_offset ? *pstring_offset : 0;
240 skip = 0;
242 symend = stabbuf + stabsec->size;
243 for (sym = stabbuf, pstridx = secinfo->stridxs;
244 sym < symend;
245 sym += STABSIZE, ++pstridx)
247 bfd_size_type symstroff;
248 int type;
249 const char *string;
251 if (*pstridx != 0)
252 /* This symbol has already been handled by an N_BINCL pass. */
253 continue;
255 type = sym[TYPEOFF];
257 if (type == 0)
259 /* Special type 0 stabs indicate the offset to the next
260 string table. We only copy the very first one. */
261 stroff = next_stroff;
262 next_stroff += bfd_get_32 (abfd, sym + 8);
263 if (pstring_offset)
264 *pstring_offset = next_stroff;
265 if (! first)
267 *pstridx = (bfd_size_type) -1;
268 ++skip;
269 continue;
271 first = FALSE;
274 /* Store the string in the hash table, and record the index. */
275 symstroff = stroff + bfd_get_32 (abfd, sym + STRDXOFF);
276 if (symstroff >= stabstrsec->size)
278 (*_bfd_error_handler)
279 (_("%B(%A+0x%lx): Stabs entry has invalid string index."),
280 abfd, stabsec, (long) (sym - stabbuf));
281 bfd_set_error (bfd_error_bad_value);
282 goto error_return;
284 string = (char *) stabstrbuf + symstroff;
285 *pstridx = _bfd_stringtab_add (sinfo->strings, string, TRUE, TRUE);
287 /* An N_BINCL symbol indicates the start of the stabs entries
288 for a header file. We need to scan ahead to the next N_EINCL
289 symbol, ignoring nesting, adding up all the characters in the
290 symbol names, not including the file numbers in types (the
291 first number after an open parenthesis). */
292 if (type == (int) N_BINCL)
294 bfd_vma sum_chars;
295 bfd_vma num_chars;
296 bfd_vma buf_len = 0;
297 char * symb;
298 char * symb_rover;
299 int nest;
300 bfd_byte * incl_sym;
301 struct stab_link_includes_entry * incl_entry;
302 struct stab_link_includes_totals * t;
303 struct stab_excl_list * ne;
305 symb = symb_rover = NULL;
306 sum_chars = num_chars = 0;
307 nest = 0;
309 for (incl_sym = sym + STABSIZE;
310 incl_sym < symend;
311 incl_sym += STABSIZE)
313 int incl_type;
315 incl_type = incl_sym[TYPEOFF];
316 if (incl_type == 0)
317 break;
318 else if (incl_type == (int) N_EXCL)
319 continue;
320 else if (incl_type == (int) N_EINCL)
322 if (nest == 0)
323 break;
324 --nest;
326 else if (incl_type == (int) N_BINCL)
327 ++nest;
328 else if (nest == 0)
330 const char *str;
332 str = ((char *) stabstrbuf
333 + stroff
334 + bfd_get_32 (abfd, incl_sym + STRDXOFF));
335 for (; *str != '\0'; str++)
337 if (num_chars >= buf_len)
339 buf_len += 32 * 1024;
340 symb = (char *) bfd_realloc_or_free (symb, buf_len);
341 if (symb == NULL)
342 goto error_return;
343 symb_rover = symb + num_chars;
345 * symb_rover ++ = * str;
346 sum_chars += *str;
347 num_chars ++;
348 if (*str == '(')
350 /* Skip the file number. */
351 ++str;
352 while (ISDIGIT (*str))
353 ++str;
354 --str;
360 BFD_ASSERT (num_chars == (bfd_vma) (symb_rover - symb));
362 /* If we have already included a header file with the same
363 value, then replaced this one with an N_EXCL symbol. */
364 incl_entry = (struct stab_link_includes_entry * )
365 bfd_hash_lookup (&sinfo->includes, string, TRUE, TRUE);
366 if (incl_entry == NULL)
367 goto error_return;
369 for (t = incl_entry->totals; t != NULL; t = t->next)
370 if (t->sum_chars == sum_chars
371 && t->num_chars == num_chars
372 && memcmp (t->symb, symb, num_chars) == 0)
373 break;
375 /* Record this symbol, so that we can set the value
376 correctly. */
377 amt = sizeof *ne;
378 ne = (struct stab_excl_list *) bfd_alloc (abfd, amt);
379 if (ne == NULL)
380 goto error_return;
381 ne->offset = sym - stabbuf;
382 ne->val = sum_chars;
383 ne->type = (int) N_BINCL;
384 ne->next = secinfo->excls;
385 secinfo->excls = ne;
387 if (t == NULL)
389 /* This is the first time we have seen this header file
390 with this set of stabs strings. */
391 t = (struct stab_link_includes_totals *)
392 bfd_hash_allocate (&sinfo->includes, sizeof *t);
393 if (t == NULL)
394 goto error_return;
395 t->sum_chars = sum_chars;
396 t->num_chars = num_chars;
397 /* Trim data down. */
398 t->symb = symb = (char *) bfd_realloc_or_free (symb, num_chars);
399 t->next = incl_entry->totals;
400 incl_entry->totals = t;
402 else
404 bfd_size_type *incl_pstridx;
406 /* We have seen this header file before. Tell the final
407 pass to change the type to N_EXCL. */
408 ne->type = (int) N_EXCL;
410 /* Free off superfluous symbols. */
411 free (symb);
413 /* Mark the skipped symbols. */
415 nest = 0;
416 for (incl_sym = sym + STABSIZE, incl_pstridx = pstridx + 1;
417 incl_sym < symend;
418 incl_sym += STABSIZE, ++incl_pstridx)
420 int incl_type;
422 incl_type = incl_sym[TYPEOFF];
424 if (incl_type == (int) N_EINCL)
426 if (nest == 0)
428 *incl_pstridx = (bfd_size_type) -1;
429 ++skip;
430 break;
432 --nest;
434 else if (incl_type == (int) N_BINCL)
435 ++nest;
436 else if (incl_type == (int) N_EXCL)
437 /* Keep existing exclusion marks. */
438 continue;
439 else if (nest == 0)
441 *incl_pstridx = (bfd_size_type) -1;
442 ++skip;
449 free (stabbuf);
450 stabbuf = NULL;
451 free (stabstrbuf);
452 stabstrbuf = NULL;
454 /* We need to set the section sizes such that the linker will
455 compute the output section sizes correctly. We set the .stab
456 size to not include the entries we don't want. We set
457 SEC_EXCLUDE for the .stabstr section, so that it will be dropped
458 from the link. We record the size of the strtab in the first
459 .stabstr section we saw, and make sure we don't set SEC_EXCLUDE
460 for that section. */
461 stabsec->size = (count - skip) * STABSIZE;
462 if (stabsec->size == 0)
463 stabsec->flags |= SEC_EXCLUDE | SEC_KEEP;
464 stabstrsec->flags |= SEC_EXCLUDE | SEC_KEEP;
465 sinfo->stabstr->size = _bfd_stringtab_size (sinfo->strings);
467 /* Calculate the `cumulative_skips' array now that stabs have been
468 deleted for this section. */
470 if (skip != 0)
472 bfd_size_type i, offset;
473 bfd_size_type *pskips;
475 amt = count * sizeof (bfd_size_type);
476 secinfo->cumulative_skips = (bfd_size_type *) bfd_alloc (abfd, amt);
477 if (secinfo->cumulative_skips == NULL)
478 goto error_return;
480 pskips = secinfo->cumulative_skips;
481 pstridx = secinfo->stridxs;
482 offset = 0;
484 for (i = 0; i < count; i++, pskips++, pstridx++)
486 *pskips = offset;
487 if (*pstridx == (bfd_size_type) -1)
488 offset += STABSIZE;
491 BFD_ASSERT (offset != 0);
494 return TRUE;
496 error_return:
497 if (stabbuf != NULL)
498 free (stabbuf);
499 if (stabstrbuf != NULL)
500 free (stabstrbuf);
501 return FALSE;
504 /* This function is called for each input file before the stab
505 section is relocated. It discards stab entries for discarded
506 functions and variables. The function returns TRUE iff
507 any entries have been deleted.
510 bfd_boolean
511 _bfd_discard_section_stabs (bfd *abfd,
512 asection *stabsec,
513 void * psecinfo,
514 bfd_boolean (*reloc_symbol_deleted_p) (bfd_vma, void *),
515 void * cookie)
517 bfd_size_type count, amt;
518 struct stab_section_info *secinfo;
519 bfd_byte *stabbuf = NULL;
520 bfd_byte *sym, *symend;
521 bfd_size_type skip;
522 bfd_size_type *pstridx;
523 int deleting;
525 if (stabsec->size == 0)
526 /* This file does not contain stabs debugging information. */
527 return FALSE;
529 if (stabsec->size % STABSIZE != 0)
530 /* Something is wrong with the format of these stab symbols.
531 Don't try to optimize them. */
532 return FALSE;
534 if ((stabsec->output_section != NULL
535 && bfd_is_abs_section (stabsec->output_section)))
536 /* At least one of the sections is being discarded from the
537 link, so we should just ignore them. */
538 return FALSE;
540 /* We should have initialized our data in _bfd_link_stab_sections.
541 If there was some bizarre error reading the string sections, though,
542 we might not have. Bail rather than asserting. */
543 if (psecinfo == NULL)
544 return FALSE;
546 count = stabsec->rawsize / STABSIZE;
547 secinfo = (struct stab_section_info *) psecinfo;
549 /* Read the stabs information from abfd. */
550 if (!bfd_malloc_and_get_section (abfd, stabsec, &stabbuf))
551 goto error_return;
553 /* Look through the stabs symbols and discard any information for
554 discarded functions. */
555 skip = 0;
556 deleting = -1;
558 symend = stabbuf + stabsec->rawsize;
559 for (sym = stabbuf, pstridx = secinfo->stridxs;
560 sym < symend;
561 sym += STABSIZE, ++pstridx)
563 int type;
565 if (*pstridx == (bfd_size_type) -1)
566 /* This stab was deleted in a previous pass. */
567 continue;
569 type = sym[TYPEOFF];
571 if (type == (int) N_FUN)
573 int strx = bfd_get_32 (abfd, sym + STRDXOFF);
575 if (strx == 0)
577 if (deleting)
579 skip++;
580 *pstridx = -1;
582 deleting = -1;
583 continue;
585 deleting = 0;
586 if ((*reloc_symbol_deleted_p) (sym + VALOFF - stabbuf, cookie))
587 deleting = 1;
590 if (deleting == 1)
592 *pstridx = -1;
593 skip++;
595 else if (deleting == -1)
597 /* Outside of a function. Check for deleted variables. */
598 if (type == (int) N_STSYM || type == (int) N_LCSYM)
599 if ((*reloc_symbol_deleted_p) (sym + VALOFF - stabbuf, cookie))
601 *pstridx = -1;
602 skip ++;
604 /* We should also check for N_GSYM entries which reference a
605 deleted global, but those are less harmful to debuggers
606 and would require parsing the stab strings. */
610 free (stabbuf);
611 stabbuf = NULL;
613 /* Shrink the stabsec as needed. */
614 stabsec->size -= skip * STABSIZE;
615 if (stabsec->size == 0)
616 stabsec->flags |= SEC_EXCLUDE | SEC_KEEP;
618 /* Recalculate the `cumulative_skips' array now that stabs have been
619 deleted for this section. */
621 if (skip != 0)
623 bfd_size_type i, offset;
624 bfd_size_type *pskips;
626 if (secinfo->cumulative_skips == NULL)
628 amt = count * sizeof (bfd_size_type);
629 secinfo->cumulative_skips = (bfd_size_type *) bfd_alloc (abfd, amt);
630 if (secinfo->cumulative_skips == NULL)
631 goto error_return;
634 pskips = secinfo->cumulative_skips;
635 pstridx = secinfo->stridxs;
636 offset = 0;
638 for (i = 0; i < count; i++, pskips++, pstridx++)
640 *pskips = offset;
641 if (*pstridx == (bfd_size_type) -1)
642 offset += STABSIZE;
645 BFD_ASSERT (offset != 0);
648 return skip > 0;
650 error_return:
651 if (stabbuf != NULL)
652 free (stabbuf);
653 return FALSE;
656 /* Write out the stab section. This is called with the relocated
657 contents. */
659 bfd_boolean
660 _bfd_write_section_stabs (bfd *output_bfd,
661 struct stab_info *sinfo,
662 asection *stabsec,
663 void * *psecinfo,
664 bfd_byte *contents)
666 struct stab_section_info *secinfo;
667 struct stab_excl_list *e;
668 bfd_byte *sym, *tosym, *symend;
669 bfd_size_type *pstridx;
671 secinfo = (struct stab_section_info *) *psecinfo;
673 if (secinfo == NULL)
674 return bfd_set_section_contents (output_bfd, stabsec->output_section,
675 contents, stabsec->output_offset,
676 stabsec->size);
678 /* Handle each N_BINCL entry. */
679 for (e = secinfo->excls; e != NULL; e = e->next)
681 bfd_byte *excl_sym;
683 BFD_ASSERT (e->offset < stabsec->rawsize);
684 excl_sym = contents + e->offset;
685 bfd_put_32 (output_bfd, e->val, excl_sym + VALOFF);
686 excl_sym[TYPEOFF] = e->type;
689 /* Copy over all the stabs symbols, omitting the ones we don't want,
690 and correcting the string indices for those we do want. */
691 tosym = contents;
692 symend = contents + stabsec->rawsize;
693 for (sym = contents, pstridx = secinfo->stridxs;
694 sym < symend;
695 sym += STABSIZE, ++pstridx)
697 if (*pstridx != (bfd_size_type) -1)
699 if (tosym != sym)
700 memcpy (tosym, sym, STABSIZE);
701 bfd_put_32 (output_bfd, *pstridx, tosym + STRDXOFF);
703 if (sym[TYPEOFF] == 0)
705 /* This is the header symbol for the stabs section. We
706 don't really need one, since we have merged all the
707 input stabs sections into one, but we generate one
708 for the benefit of readers which expect to see one. */
709 BFD_ASSERT (sym == contents);
710 bfd_put_32 (output_bfd, _bfd_stringtab_size (sinfo->strings),
711 tosym + VALOFF);
712 bfd_put_16 (output_bfd,
713 stabsec->output_section->size / STABSIZE - 1,
714 tosym + DESCOFF);
717 tosym += STABSIZE;
721 BFD_ASSERT ((bfd_size_type) (tosym - contents) == stabsec->size);
723 return bfd_set_section_contents (output_bfd, stabsec->output_section,
724 contents, (file_ptr) stabsec->output_offset,
725 stabsec->size);
728 /* Write out the .stabstr section. */
730 bfd_boolean
731 _bfd_write_stab_strings (bfd *output_bfd, struct stab_info *sinfo)
733 if (bfd_is_abs_section (sinfo->stabstr->output_section))
734 /* The section was discarded from the link. */
735 return TRUE;
737 BFD_ASSERT ((sinfo->stabstr->output_offset
738 + _bfd_stringtab_size (sinfo->strings))
739 <= sinfo->stabstr->output_section->size);
741 if (bfd_seek (output_bfd,
742 (file_ptr) (sinfo->stabstr->output_section->filepos
743 + sinfo->stabstr->output_offset),
744 SEEK_SET) != 0)
745 return FALSE;
747 if (! _bfd_stringtab_emit (output_bfd, sinfo->strings))
748 return FALSE;
750 /* We no longer need the stabs information. */
751 _bfd_stringtab_free (sinfo->strings);
752 bfd_hash_table_free (&sinfo->includes);
754 return TRUE;
757 /* Adjust an address in the .stab section. Given OFFSET within
758 STABSEC, this returns the new offset in the adjusted stab section,
759 or -1 if the address refers to a stab which has been removed. */
761 bfd_vma
762 _bfd_stab_section_offset (asection *stabsec,
763 void * psecinfo,
764 bfd_vma offset)
766 struct stab_section_info *secinfo;
768 secinfo = (struct stab_section_info *) psecinfo;
770 if (secinfo == NULL)
771 return offset;
773 if (offset >= stabsec->rawsize)
774 return offset - stabsec->rawsize + stabsec->size;
776 if (secinfo->cumulative_skips)
778 bfd_vma i;
780 i = offset / STABSIZE;
782 if (secinfo->stridxs [i] == (bfd_size_type) -1)
783 return (bfd_vma) -1;
785 return offset - secinfo->cumulative_skips [i];
788 return offset;