new file.

[binutils.git] / bfd / syms.c

/* Generic symbol-table support for the BFD library.
   Copyright (C) 1990, 1991, 1992, 1993 Free Software Foundation, Inc.
   Written by Cygnus Support.

This file is part of BFD, the Binary File Descriptor library.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

/*
SECTION
        Symbols

        BFD tries to maintain as much symbol information as it can when
        it moves information from file to file. BFD passes information
        to applications though the <<asymbol>> structure. When the
        application requests the symbol table, BFD reads the table in
        the native form and translates parts of it into the internal
        format. To maintain more than the information passed to
        applications, some targets keep some information ``behind the
        scenes'' in a structure only the particular back end knows
        about. For example, the coff back end keeps the original
        symbol table structure as well as the canonical structure when
        a BFD is read in. On output, the coff back end can reconstruct
        the output symbol table so that no information is lost, even
        information unique to coff which BFD doesn't know or
        understand. If a coff symbol table were read, but were written
        through an a.out back end, all the coff specific information
        would be lost. The symbol table of a BFD
        is not necessarily read in until a canonicalize request is
        made. Then the BFD back end fills in a table provided by the
        application with pointers to the canonical information.  To
        output symbols, the application provides BFD with a table of
        pointers to pointers to <<asymbol>>s. This allows applications
        like the linker to output a symbol as it was read, since the ``behind
        the scenes'' information will be still available.
@menu
@* Reading Symbols::
@* Writing Symbols::
@* typedef asymbol::
@* symbol handling functions::
@end menu

INODE
Reading Symbols, Writing Symbols, Symbols, Symbols
SUBSECTION
        Reading symbols

        There are two stages to reading a symbol table from a BFD:
        allocating storage, and the actual reading process. This is an
        excerpt from an application which reads the symbol table:

|         long storage_needed;
|         asymbol **symbol_table;
|         long number_of_symbols;
|         long i;
|
|         storage_needed = bfd_get_symtab_upper_bound (abfd);
|
|         if (storage_needed < 0)
|           FAIL
|
|         if (storage_needed == 0) {
|            return ;
|         }
|         symbol_table = (asymbol **) xmalloc (storage_needed);
|           ...
|         number_of_symbols =
|            bfd_canonicalize_symtab (abfd, symbol_table);
|
|         if (number_of_symbols < 0)
|           FAIL
|
|         for (i = 0; i < number_of_symbols; i++) {
|            process_symbol (symbol_table[i]);
|         }

        All storage for the symbols themselves is in an obstack
        connected to the BFD; it is freed when the BFD is closed.


INODE
Writing Symbols, Mini symbols, Reading Symbols, Symbols
SUBSECTION
        Writing symbols

        Writing of a symbol table is automatic when a BFD open for
        writing is closed. The application attaches a vector of
        pointers to pointers to symbols to the BFD being written, and
        fills in the symbol count. The close and cleanup code reads
        through the table provided and performs all the necessary
        operations. The BFD output code must always be provided with an
        ``owned'' symbol: one which has come from another BFD, or one
        which has been created using <<bfd_make_empty_symbol>>.  Here is an
        example showing the creation of a symbol table with only one element:

|       #include "bfd.h"
|       main()
|       {
|         bfd *abfd;
|         asymbol *ptrs[2];
|         asymbol *new;
|
|         abfd = bfd_openw("foo","a.out-sunos-big");
|         bfd_set_format(abfd, bfd_object);
|         new = bfd_make_empty_symbol(abfd);
|         new->name = "dummy_symbol";
|         new->section = bfd_make_section_old_way(abfd, ".text");
|         new->flags = BSF_GLOBAL;
|         new->value = 0x12345;
|
|         ptrs[0] = new;
|         ptrs[1] = (asymbol *)0;
|
|         bfd_set_symtab(abfd, ptrs, 1);
|         bfd_close(abfd);
|       }
|
|       ./makesym
|       nm foo
|       00012345 A dummy_symbol

        Many formats cannot represent arbitary symbol information; for
        instance, the <<a.out>> object format does not allow an
        arbitary number of sections. A symbol pointing to a section
        which is not one  of <<.text>>, <<.data>> or <<.bss>> cannot
        be described.

INODE
Mini symbols, typedef asymbol, Writing Symbols, Symbols
SUBSECTION
        Mini symbols

        Mini symbols provide read-only access to the symbol table.
        They use less memory space, but require more time to access.
        They can be useful for tools like nm or objdump, which may
        have to handle symbol tables of extremely large executables.

        The <<bfd_read_minisymbols>> function will read the symbols
        into memory in an internal form.  It will return a <<void *>>
        pointer to a block of memory, a symbol count, and the size of
        each symbol.  The pointer is allocated using <<malloc>>, and
        should be freed by the caller when it is no longer needed.

        The function <<bfd_minisymbol_to_symbol>> will take a pointer
        to a minisymbol, and a pointer to a structure returned by
        <<bfd_make_empty_symbol>>, and return a <<asymbol>> structure.
        The return value may or may not be the same as the value from
        <<bfd_make_empty_symbol>> which was passed in.

*/



/*
DOCDD
INODE
typedef asymbol, symbol handling functions, Mini symbols, Symbols

*/
/*
SUBSECTION
        typedef asymbol

        An <<asymbol>> has the form:

*/

/*
CODE_FRAGMENT

.
.typedef struct symbol_cache_entry
.{
.       {* A pointer to the BFD which owns the symbol. This information
.          is necessary so that a back end can work out what additional
.          information (invisible to the application writer) is carried
.          with the symbol.
.
.          This field is *almost* redundant, since you can use section->owner
.          instead, except that some symbols point to the global sections
.          bfd_{abs,com,und}_section.  This could be fixed by making
.          these globals be per-bfd (or per-target-flavor).  FIXME. *}
.
.  struct _bfd *the_bfd; {* Use bfd_asymbol_bfd(sym) to access this field. *}
.
.       {* The text of the symbol. The name is left alone, and not copied; the
.          application may not alter it. *}
.  CONST char *name;
.
.       {* The value of the symbol.  This really should be a union of a
.          numeric value with a pointer, since some flags indicate that
.          a pointer to another symbol is stored here.  *}
.  symvalue value;
.
.       {* Attributes of a symbol: *}
.
.#define BSF_NO_FLAGS    0x00
.
.       {* The symbol has local scope; <<static>> in <<C>>. The value
.          is the offset into the section of the data. *}
.#define BSF_LOCAL      0x01
.
.       {* The symbol has global scope; initialized data in <<C>>. The
.          value is the offset into the section of the data. *}
.#define BSF_GLOBAL     0x02
.
.       {* The symbol has global scope and is exported. The value is
.          the offset into the section of the data. *}
.#define BSF_EXPORT     BSF_GLOBAL {* no real difference *}
.
.       {* A normal C symbol would be one of:
.          <<BSF_LOCAL>>, <<BSF_FORT_COMM>>,  <<BSF_UNDEFINED>> or
.          <<BSF_GLOBAL>> *}
.
.       {* The symbol is a debugging record. The value has an arbitary
.          meaning. *}
.#define BSF_DEBUGGING  0x08
.
.       {* The symbol denotes a function entry point.  Used in ELF,
.          perhaps others someday.  *}
.#define BSF_FUNCTION    0x10
.
.       {* Used by the linker. *}
.#define BSF_KEEP        0x20
.#define BSF_KEEP_G      0x40
.
.       {* A weak global symbol, overridable without warnings by
.          a regular global symbol of the same name.  *}
.#define BSF_WEAK        0x80
.
.       {* This symbol was created to point to a section, e.g. ELF's
.          STT_SECTION symbols.  *}
.#define BSF_SECTION_SYM 0x100
.
.       {* The symbol used to be a common symbol, but now it is
.          allocated. *}
.#define BSF_OLD_COMMON  0x200
.
.       {* The default value for common data. *}
.#define BFD_FORT_COMM_DEFAULT_VALUE 0
.
.       {* In some files the type of a symbol sometimes alters its
.          location in an output file - ie in coff a <<ISFCN>> symbol
.          which is also <<C_EXT>> symbol appears where it was
.          declared and not at the end of a section.  This bit is set
.          by the target BFD part to convey this information. *}
.
.#define BSF_NOT_AT_END    0x400
.
.       {* Signal that the symbol is the label of constructor section. *}
.#define BSF_CONSTRUCTOR   0x800
.
.       {* Signal that the symbol is a warning symbol. If the symbol
.          is a warning symbol, then the value field (I know this is
.          tacky) will point to the asymbol which when referenced will
.          cause the warning. *}
.#define BSF_WARNING       0x1000
.
.       {* Signal that the symbol is indirect. The value of the symbol
.          is a pointer to an undefined asymbol which contains the
.          name to use instead. *}
.#define BSF_INDIRECT      0x2000
.
.       {* BSF_FILE marks symbols that contain a file name.  This is used
.          for ELF STT_FILE symbols.  *}
.#define BSF_FILE          0x4000
.
.       {* Symbol is from dynamic linking information.  *}
.#define BSF_DYNAMIC       0x8000
.
.  flagword flags;
.
.       {* A pointer to the section to which this symbol is
.          relative.  This will always be non NULL, there are special
.          sections for undefined and absolute symbols.  *}
.  struct sec *section;
.
.       {* Back end special data.  *}
.  union
.    {
.      PTR p;
.      bfd_vma i;
.    } udata;
.
.} asymbol;
*/

#include "bfd.h"
#include "sysdep.h"

#include "libbfd.h"
#include "aout/stab_gnu.h"

/*
DOCDD
INODE
symbol handling functions,  , typedef asymbol, Symbols
SUBSECTION
        Symbol handling functions
*/

/*
FUNCTION
        bfd_get_symtab_upper_bound

DESCRIPTION
        Return the number of bytes required to store a vector of pointers
        to <<asymbols>> for all the symbols in the BFD @var{abfd},
        including a terminal NULL pointer. If there are no symbols in
        the BFD, then return 0.  If an error occurs, return -1.

.#define bfd_get_symtab_upper_bound(abfd) \
.     BFD_SEND (abfd, _bfd_get_symtab_upper_bound, (abfd))

*/

/*
FUNCTION
        bfd_is_local_label

SYNOPSIS
        boolean bfd_is_local_label(bfd *abfd, asymbol *sym);

DESCRIPTION
        Return true if the given symbol @var{sym} in the BFD @var{abfd} is
        a compiler generated local label, else return false.
.#define bfd_is_local_label(abfd, sym) \
.     BFD_SEND (abfd, _bfd_is_local_label,(abfd, sym))
*/

/*
FUNCTION
        bfd_canonicalize_symtab

DESCRIPTION
        Read the symbols from the BFD @var{abfd}, and fills in
        the vector @var{location} with pointers to the symbols and
        a trailing NULL.
        Return the actual number of symbol pointers, not
        including the NULL.


.#define bfd_canonicalize_symtab(abfd, location) \
.     BFD_SEND (abfd, _bfd_canonicalize_symtab,\
.                  (abfd, location))

*/


/*
FUNCTION
        bfd_set_symtab

SYNOPSIS
        boolean bfd_set_symtab (bfd *abfd, asymbol **location, unsigned int count);

DESCRIPTION
        Arrange that when the output BFD @var{abfd} is closed,
        the table @var{location} of @var{count} pointers to symbols
        will be written.
*/

boolean
bfd_set_symtab (abfd, location, symcount)
     bfd *abfd;
     asymbol **location;
     unsigned int symcount;
{
  if ((abfd->format != bfd_object) || (bfd_read_p (abfd)))
    {
      bfd_set_error (bfd_error_invalid_operation);
      return false;
    }

  bfd_get_outsymbols (abfd) = location;
  bfd_get_symcount (abfd) = symcount;
  return true;
}

/*
FUNCTION
        bfd_print_symbol_vandf

SYNOPSIS
        void bfd_print_symbol_vandf(PTR file, asymbol *symbol);

DESCRIPTION
        Print the value and flags of the @var{symbol} supplied to the
        stream @var{file}.
*/
void
bfd_print_symbol_vandf (arg, symbol)
     PTR arg;
     asymbol *symbol;
{
  FILE *file = (FILE *) arg;
  flagword type = symbol->flags;
  if (symbol->section != (asection *) NULL)
    {
      fprintf_vma (file, symbol->value + symbol->section->vma);
    }
  else
    {
      fprintf_vma (file, symbol->value);
    }

  /* This presumes that a symbol can not be both BSF_DEBUGGING and
     BSF_DYNAMIC, nor both BSF_FUNCTION and BSF_FILE.  */
  fprintf (file, " %c%c%c%c%c%c%c",
           ((type & BSF_LOCAL)
            ? (type & BSF_GLOBAL) ? '!' : 'l'
            : (type & BSF_GLOBAL) ? 'g' : ' '),
           (type & BSF_WEAK) ? 'w' : ' ',
           (type & BSF_CONSTRUCTOR) ? 'C' : ' ',
           (type & BSF_WARNING) ? 'W' : ' ',
           (type & BSF_INDIRECT) ? 'I' : ' ',
           (type & BSF_DEBUGGING) ? 'd' : (type & BSF_DYNAMIC) ? 'D' : ' ',
           (type & BSF_FUNCTION) ? 'F' : (type & BSF_FILE) ? 'f' : ' ');
}


/*
FUNCTION
        bfd_make_empty_symbol

DESCRIPTION
        Create a new <<asymbol>> structure for the BFD @var{abfd}
        and return a pointer to it.

        This routine is necessary because each back end has private
        information surrounding the <<asymbol>>. Building your own
        <<asymbol>> and pointing to it will not create the private
        information, and will cause problems later on.

.#define bfd_make_empty_symbol(abfd) \
.     BFD_SEND (abfd, _bfd_make_empty_symbol, (abfd))
*/

/*
FUNCTION
        bfd_make_debug_symbol

DESCRIPTION
        Create a new <<asymbol>> structure for the BFD @var{abfd},
        to be used as a debugging symbol.  Further details of its use have
        yet to be worked out.

.#define bfd_make_debug_symbol(abfd,ptr,size) \
.        BFD_SEND (abfd, _bfd_make_debug_symbol, (abfd, ptr, size))
*/

struct section_to_type
{
  CONST char *section;
  char type;
};

/* Map section names to POSIX/BSD single-character symbol types.
   This table is probably incomplete.  It is sorted for convenience of
   adding entries.  Since it is so short, a linear search is used.  */
static CONST struct section_to_type stt[] =
{
  {"*DEBUG*", 'N'},
  {".bss", 'b'},
  {".data", 'd'},
  {".rdata", 'r'},              /* Read only data.  */
  {".rodata", 'r'},             /* Read only data.  */
  {".sbss", 's'},               /* Small BSS (uninitialized data).  */
  {".scommon", 'c'},            /* Small common.  */
  {".sdata", 'g'},              /* Small initialized data.  */
  {".text", 't'},
  {0, 0}
};

/* Return the single-character symbol type corresponding to
   section S, or '?' for an unknown COFF section.  

   Check for any leading string which matches, so .text5 returns
   't' as well as .text */

static char
coff_section_type (s)
     char *s;
{
  CONST struct section_to_type *t;

  for (t = &stt[0]; t->section; t++) 
    if (!strncmp (s, t->section, strlen (t->section)))
      return t->type;

  return '?';
}

#ifndef islower
#define islower(c) ((c) >= 'a' && (c) <= 'z')
#endif
#ifndef toupper
#define toupper(c) (islower(c) ? ((c) & ~0x20) : (c))
#endif

/*
FUNCTION
        bfd_decode_symclass

DESCRIPTION
        Return a character corresponding to the symbol
        class of @var{symbol}, or '?' for an unknown class.

SYNOPSIS
        int bfd_decode_symclass(asymbol *symbol);
*/
int
bfd_decode_symclass (symbol)
     asymbol *symbol;
{
  char c;

  if (bfd_is_com_section (symbol->section))
    return 'C';
  if (bfd_is_und_section (symbol->section))
    return 'U';
  if (bfd_is_ind_section (symbol->section))
    return 'I';
  if (symbol->flags & BSF_WEAK)
    return 'W';
  if (!(symbol->flags & (BSF_GLOBAL | BSF_LOCAL)))
    return '?';

  if (bfd_is_abs_section (symbol->section))
    c = 'a';
  else if (symbol->section)
    c = coff_section_type (symbol->section->name);
  else
    return '?';
  if (symbol->flags & BSF_GLOBAL)
    c = toupper (c);
  return c;

  /* We don't have to handle these cases just yet, but we will soon:
     N_SETV: 'v';
     N_SETA: 'l';
     N_SETT: 'x';
     N_SETD: 'z';
     N_SETB: 's';
     N_INDR: 'i';
     */
}

/*
FUNCTION
        bfd_symbol_info

DESCRIPTION
        Fill in the basic info about symbol that nm needs.
        Additional info may be added by the back-ends after
        calling this function.

SYNOPSIS
        void bfd_symbol_info(asymbol *symbol, symbol_info *ret);
*/

void
bfd_symbol_info (symbol, ret)
     asymbol *symbol;
     symbol_info *ret;
{
  ret->type = bfd_decode_symclass (symbol);
  if (ret->type != 'U')
    ret->value = symbol->value + symbol->section->vma;
  else
    ret->value = 0;
  ret->name = symbol->name;
}

void
bfd_symbol_is_absolute ()
{
  abort ();
}

/*
FUNCTION
        bfd_copy_private_symbol_data

SYNOPSIS
        boolean bfd_copy_private_symbol_data(bfd *ibfd, asymbol *isym, bfd *obfd, asymbol *osym);

DESCRIPTION
        Copy private symbol information from @var{isym} in the BFD
        @var{ibfd} to the symbol @var{osym} in the BFD @var{obfd}.
        Return <<true>> on success, <<false>> on error.  Possible error
        returns are:

        o <<bfd_error_no_memory>> -
        Not enough memory exists to create private data for @var{osec}.

.#define bfd_copy_private_symbol_data(ibfd, isymbol, obfd, osymbol) \
.     BFD_SEND (ibfd, _bfd_copy_private_symbol_data, \
.               (ibfd, isymbol, obfd, osymbol))

*/

/* The generic version of the function which returns mini symbols.
   This is used when the backend does not provide a more efficient
   version.  It just uses BFD asymbol structures as mini symbols.  */

long
_bfd_generic_read_minisymbols (abfd, dynamic, minisymsp, sizep)
     bfd *abfd;
     boolean dynamic;
     PTR *minisymsp;
     unsigned int *sizep;
{
  long storage;
  asymbol **syms = NULL;
  long symcount;

  if (dynamic)
    storage = bfd_get_dynamic_symtab_upper_bound (abfd);
  else
    storage = bfd_get_symtab_upper_bound (abfd);
  if (storage < 0)
    goto error_return;

  syms = (asymbol **) malloc ((size_t) storage);
  if (syms == NULL)
    {
      bfd_set_error (bfd_error_no_memory);
      goto error_return;
    }

  if (dynamic)
    symcount = bfd_canonicalize_dynamic_symtab (abfd, syms);
  else
    symcount = bfd_canonicalize_symtab (abfd, syms);
  if (symcount < 0)
    goto error_return;

  *minisymsp = (PTR) syms;
  *sizep = sizeof (asymbol *);
  return symcount;

 error_return:
  if (syms != NULL)
    free (syms);
  return -1;
}

/* The generic version of the function which converts a minisymbol to
   an asymbol.  We don't worry about the sym argument we are passed;
   we just return the asymbol the minisymbol points to.  */

/*ARGSUSED*/
asymbol *
_bfd_generic_minisymbol_to_symbol (abfd, dynamic, minisym, sym)
     bfd *abfd;
     boolean dynamic;
     const PTR minisym;
     asymbol *sym;
{
  return *(asymbol **) minisym;
}