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[deliverable/binutils-gdb.git] / gdb / minsyms.c

/* GDB routines for manipulating the minimal symbol tables.
   Copyright (C) 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
   2002, 2003, 2004, 2007 Free Software Foundation, Inc.
   Contributed by Cygnus Support, using pieces from other GDB modules.

   This file is part of GDB.

   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., 51 Franklin Street, Fifth Floor,
   Boston, MA 02110-1301, USA.  */


/* This file contains support routines for creating, manipulating, and
   destroying minimal symbol tables.

   Minimal symbol tables are used to hold some very basic information about
   all defined global symbols (text, data, bss, abs, etc).  The only two
   required pieces of information are the symbol's name and the address
   associated with that symbol.

   In many cases, even if a file was compiled with no special options for
   debugging at all, as long as was not stripped it will contain sufficient
   information to build useful minimal symbol tables using this structure.

   Even when a file contains enough debugging information to build a full
   symbol table, these minimal symbols are still useful for quickly mapping
   between names and addresses, and vice versa.  They are also sometimes used
   to figure out what full symbol table entries need to be read in. */


#include "defs.h"
#include <ctype.h>
#include "gdb_string.h"
#include "symtab.h"
#include "bfd.h"
#include "symfile.h"
#include "objfiles.h"
#include "demangle.h"
#include "value.h"
#include "cp-abi.h"

/* Accumulate the minimal symbols for each objfile in bunches of BUNCH_SIZE.
   At the end, copy them all into one newly allocated location on an objfile's
   symbol obstack.  */

#define BUNCH_SIZE 127

struct msym_bunch
  {
    struct msym_bunch *next;
    struct minimal_symbol contents[BUNCH_SIZE];
  };

/* Bunch currently being filled up.
   The next field points to chain of filled bunches.  */

static struct msym_bunch *msym_bunch;

/* Number of slots filled in current bunch.  */

static int msym_bunch_index;

/* Total number of minimal symbols recorded so far for the objfile.  */

static int msym_count;

/* Compute a hash code based using the same criteria as `strcmp_iw'.  */

unsigned int
msymbol_hash_iw (const char *string)
{
  unsigned int hash = 0;
  while (*string && *string != '(')
    {
      while (isspace (*string))
        ++string;
      if (*string && *string != '(')
        {
          hash = hash * 67 + *string - 113;
          ++string;
        }
    }
  return hash;
}

/* Compute a hash code for a string.  */

unsigned int
msymbol_hash (const char *string)
{
  unsigned int hash = 0;
  for (; *string; ++string)
    hash = hash * 67 + *string - 113;
  return hash;
}

/* Add the minimal symbol SYM to an objfile's minsym hash table, TABLE.  */
void
add_minsym_to_hash_table (struct minimal_symbol *sym,
                          struct minimal_symbol **table)
{
  if (sym->hash_next == NULL)
    {
      unsigned int hash
        = msymbol_hash (SYMBOL_LINKAGE_NAME (sym)) % MINIMAL_SYMBOL_HASH_SIZE;
      sym->hash_next = table[hash];
      table[hash] = sym;
    }
}

/* Add the minimal symbol SYM to an objfile's minsym demangled hash table,
   TABLE.  */
static void
add_minsym_to_demangled_hash_table (struct minimal_symbol *sym,
                                  struct minimal_symbol **table)
{
  if (sym->demangled_hash_next == NULL)
    {
      unsigned int hash = msymbol_hash_iw (SYMBOL_DEMANGLED_NAME (sym)) % MINIMAL_SYMBOL_HASH_SIZE;
      sym->demangled_hash_next = table[hash];
      table[hash] = sym;
    }
}


/* Look through all the current minimal symbol tables and find the
   first minimal symbol that matches NAME.  If OBJF is non-NULL, limit
   the search to that objfile.  If SFILE is non-NULL, the only file-scope
   symbols considered will be from that source file (global symbols are
   still preferred).  Returns a pointer to the minimal symbol that
   matches, or NULL if no match is found.

   Note:  One instance where there may be duplicate minimal symbols with
   the same name is when the symbol tables for a shared library and the
   symbol tables for an executable contain global symbols with the same
   names (the dynamic linker deals with the duplication).

   It's also possible to have minimal symbols with different mangled
   names, but identical demangled names.  For example, the GNU C++ v3
   ABI requires the generation of two (or perhaps three) copies of
   constructor functions --- "in-charge", "not-in-charge", and
   "allocate" copies; destructors may be duplicated as well.
   Obviously, there must be distinct mangled names for each of these,
   but the demangled names are all the same: S::S or S::~S.  */

struct minimal_symbol *
lookup_minimal_symbol (const char *name, const char *sfile,
                       struct objfile *objf)
{
  struct objfile *objfile;
  struct minimal_symbol *msymbol;
  struct minimal_symbol *found_symbol = NULL;
  struct minimal_symbol *found_file_symbol = NULL;
  struct minimal_symbol *trampoline_symbol = NULL;

  unsigned int hash = msymbol_hash (name) % MINIMAL_SYMBOL_HASH_SIZE;
  unsigned int dem_hash = msymbol_hash_iw (name) % MINIMAL_SYMBOL_HASH_SIZE;

#ifdef SOFUN_ADDRESS_MAYBE_MISSING
  if (sfile != NULL)
    {
      char *p = strrchr (sfile, '/');
      if (p != NULL)
        sfile = p + 1;
    }
#endif

  for (objfile = object_files;
       objfile != NULL && found_symbol == NULL;
       objfile = objfile->next)
    {
      if (objf == NULL || objf == objfile)
        {
          /* Do two passes: the first over the ordinary hash table,
             and the second over the demangled hash table.  */
        int pass;

        for (pass = 1; pass <= 2 && found_symbol == NULL; pass++)
            {
            /* Select hash list according to pass.  */
            if (pass == 1)
              msymbol = objfile->msymbol_hash[hash];
            else
              msymbol = objfile->msymbol_demangled_hash[dem_hash];

            while (msymbol != NULL && found_symbol == NULL)
                {
                  /* FIXME: carlton/2003-02-27: This is an unholy
                     mixture of linkage names and natural names.  If
                     you want to test the linkage names with strcmp,
                     do that.  If you want to test the natural names
                     with strcmp_iw, use SYMBOL_MATCHES_NATURAL_NAME.  */
                  if (strcmp (DEPRECATED_SYMBOL_NAME (msymbol), (name)) == 0
                      || (SYMBOL_DEMANGLED_NAME (msymbol) != NULL
                          && strcmp_iw (SYMBOL_DEMANGLED_NAME (msymbol),
                                        (name)) == 0))
                    {
                    switch (MSYMBOL_TYPE (msymbol))
                      {
                      case mst_file_text:
                      case mst_file_data:
                      case mst_file_bss:
#ifdef SOFUN_ADDRESS_MAYBE_MISSING
                        if (sfile == NULL
                            || strcmp (msymbol->filename, sfile) == 0)
                          found_file_symbol = msymbol;
#else
                        /* We have neither the ability nor the need to
                           deal with the SFILE parameter.  If we find
                           more than one symbol, just return the latest
                           one (the user can't expect useful behavior in
                           that case).  */
                        found_file_symbol = msymbol;
#endif
                        break;

                      case mst_solib_trampoline:

                        /* If a trampoline symbol is found, we prefer to
                           keep looking for the *real* symbol. If the
                           actual symbol is not found, then we'll use the
                           trampoline entry. */
                        if (trampoline_symbol == NULL)
                          trampoline_symbol = msymbol;
                        break;

                      case mst_unknown:
                      default:
                        found_symbol = msymbol;
                        break;
                      }
                    }

                /* Find the next symbol on the hash chain.  */
                if (pass == 1)
                  msymbol = msymbol->hash_next;
                else
                  msymbol = msymbol->demangled_hash_next;
                }
            }
        }
    }
  /* External symbols are best.  */
  if (found_symbol)
    return found_symbol;

  /* File-local symbols are next best.  */
  if (found_file_symbol)
    return found_file_symbol;

  /* Symbols for shared library trampolines are next best.  */
  if (trampoline_symbol)
    return trampoline_symbol;

  return NULL;
}

/* Look through all the current minimal symbol tables and find the
   first minimal symbol that matches NAME and has text type.  If OBJF
   is non-NULL, limit the search to that objfile.  Returns a pointer
   to the minimal symbol that matches, or NULL if no match is found.

   This function only searches the mangled (linkage) names.  */

struct minimal_symbol *
lookup_minimal_symbol_text (const char *name, struct objfile *objf)
{
  struct objfile *objfile;
  struct minimal_symbol *msymbol;
  struct minimal_symbol *found_symbol = NULL;
  struct minimal_symbol *found_file_symbol = NULL;

  unsigned int hash = msymbol_hash (name) % MINIMAL_SYMBOL_HASH_SIZE;

  for (objfile = object_files;
       objfile != NULL && found_symbol == NULL;
       objfile = objfile->next)
    {
      if (objf == NULL || objf == objfile)
        {
          for (msymbol = objfile->msymbol_hash[hash];
               msymbol != NULL && found_symbol == NULL;
               msymbol = msymbol->hash_next)
            {
              if (strcmp (SYMBOL_LINKAGE_NAME (msymbol), name) == 0 &&
                  (MSYMBOL_TYPE (msymbol) == mst_text ||
                   MSYMBOL_TYPE (msymbol) == mst_file_text))
                {
                  switch (MSYMBOL_TYPE (msymbol))
                    {
                    case mst_file_text:
                      found_file_symbol = msymbol;
                      break;
                    default:
                      found_symbol = msymbol;
                      break;
                    }
                }
            }
        }
    }
  /* External symbols are best.  */
  if (found_symbol)
    return found_symbol;

  /* File-local symbols are next best.  */
  if (found_file_symbol)
    return found_file_symbol;

  return NULL;
}

/* Look through all the current minimal symbol tables and find the
   first minimal symbol that matches NAME and is a solib trampoline.
   If OBJF is non-NULL, limit the search to that objfile.  Returns a
   pointer to the minimal symbol that matches, or NULL if no match is
   found.

   This function only searches the mangled (linkage) names.  */

struct minimal_symbol *
lookup_minimal_symbol_solib_trampoline (const char *name,
                                        struct objfile *objf)
{
  struct objfile *objfile;
  struct minimal_symbol *msymbol;
  struct minimal_symbol *found_symbol = NULL;

  unsigned int hash = msymbol_hash (name) % MINIMAL_SYMBOL_HASH_SIZE;

  for (objfile = object_files;
       objfile != NULL && found_symbol == NULL;
       objfile = objfile->next)
    {
      if (objf == NULL || objf == objfile)
        {
          for (msymbol = objfile->msymbol_hash[hash];
               msymbol != NULL && found_symbol == NULL;
               msymbol = msymbol->hash_next)
            {
              if (strcmp (SYMBOL_LINKAGE_NAME (msymbol), name) == 0 &&
                  MSYMBOL_TYPE (msymbol) == mst_solib_trampoline)
                return msymbol;
            }
        }
    }

  return NULL;
}

/* Search through the minimal symbol table for each objfile and find
   the symbol whose address is the largest address that is still less
   than or equal to PC, and matches SECTION (if non-NULL).  Returns a
   pointer to the minimal symbol if such a symbol is found, or NULL if
   PC is not in a suitable range.  Note that we need to look through
   ALL the minimal symbol tables before deciding on the symbol that
   comes closest to the specified PC.  This is because objfiles can
   overlap, for example objfile A has .text at 0x100 and .data at
   0x40000 and objfile B has .text at 0x234 and .data at 0x40048.  */

struct minimal_symbol *
lookup_minimal_symbol_by_pc_section (CORE_ADDR pc, asection *section)
{
  int lo;
  int hi;
  int new;
  struct objfile *objfile;
  struct minimal_symbol *msymbol;
  struct minimal_symbol *best_symbol = NULL;
  struct obj_section *pc_section;

  /* PC has to be in a known section.  This ensures that anything
     beyond the end of the last segment doesn't appear to be part of
     the last function in the last segment.  */
  pc_section = find_pc_section (pc);
  if (pc_section == NULL)
    return NULL;

  /* NOTE: cagney/2004-01-27: Removed code (added 2003-07-19) that was
     trying to force the PC into a valid section as returned by
     find_pc_section.  It broke IRIX 6.5 mdebug which relies on this
     code returning an absolute symbol - the problem was that
     find_pc_section wasn't returning an absolute section and hence
     the code below would skip over absolute symbols.  Since the
     original problem was with finding a frame's function, and that
     uses [indirectly] lookup_minimal_symbol_by_pc, the original
     problem has been fixed by having that function use
     find_pc_section.  */

  for (objfile = object_files;
       objfile != NULL;
       objfile = objfile->next)
    {
      /* If this objfile has a minimal symbol table, go search it using
         a binary search.  Note that a minimal symbol table always consists
         of at least two symbols, a "real" symbol and the terminating
         "null symbol".  If there are no real symbols, then there is no
         minimal symbol table at all. */

      if (objfile->minimal_symbol_count > 0)
        {
          int best_zero_sized = -1;

          msymbol = objfile->msymbols;
          lo = 0;
          hi = objfile->minimal_symbol_count - 1;

          /* This code assumes that the minimal symbols are sorted by
             ascending address values.  If the pc value is greater than or
             equal to the first symbol's address, then some symbol in this
             minimal symbol table is a suitable candidate for being the
             "best" symbol.  This includes the last real symbol, for cases
             where the pc value is larger than any address in this vector.

             By iterating until the address associated with the current
             hi index (the endpoint of the test interval) is less than
             or equal to the desired pc value, we accomplish two things:
             (1) the case where the pc value is larger than any minimal
             symbol address is trivially solved, (2) the address associated
             with the hi index is always the one we want when the interation
             terminates.  In essence, we are iterating the test interval
             down until the pc value is pushed out of it from the high end.

             Warning: this code is trickier than it would appear at first. */

          /* Should also require that pc is <= end of objfile.  FIXME! */
          if (pc >= SYMBOL_VALUE_ADDRESS (&msymbol[lo]))
            {
              while (SYMBOL_VALUE_ADDRESS (&msymbol[hi]) > pc)
                {
                  /* pc is still strictly less than highest address */
                  /* Note "new" will always be >= lo */
                  new = (lo + hi) / 2;
                  if ((SYMBOL_VALUE_ADDRESS (&msymbol[new]) >= pc) ||
                      (lo == new))
                    {
                      hi = new;
                    }
                  else
                    {
                      lo = new;
                    }
                }

              /* If we have multiple symbols at the same address, we want
                 hi to point to the last one.  That way we can find the
                 right symbol if it has an index greater than hi.  */
              while (hi < objfile->minimal_symbol_count - 1
                     && (SYMBOL_VALUE_ADDRESS (&msymbol[hi])
                         == SYMBOL_VALUE_ADDRESS (&msymbol[hi + 1])))
                hi++;

              /* Skip various undesirable symbols.  */
              while (hi >= 0)
                {
                  /* Skip any absolute symbols.  This is apparently
                     what adb and dbx do, and is needed for the CM-5.
                     There are two known possible problems: (1) on
                     ELF, apparently end, edata, etc. are absolute.
                     Not sure ignoring them here is a big deal, but if
                     we want to use them, the fix would go in
                     elfread.c.  (2) I think shared library entry
                     points on the NeXT are absolute.  If we want
                     special handling for this it probably should be
                     triggered by a special mst_abs_or_lib or some
                     such.  */

                  if (msymbol[hi].type == mst_abs)
                    {
                      hi--;
                      continue;
                    }

                  /* If SECTION was specified, skip any symbol from
                     wrong section.  */
                  if (section
                      /* Some types of debug info, such as COFF,
                         don't fill the bfd_section member, so don't
                         throw away symbols on those platforms.  */
                      && SYMBOL_BFD_SECTION (&msymbol[hi]) != NULL
                      && (!matching_bfd_sections
                          (SYMBOL_BFD_SECTION (&msymbol[hi]), section)))
                    {
                      hi--;
                      continue;
                    }

                  /* If the minimal symbol has a zero size, save it
                     but keep scanning backwards looking for one with
                     a non-zero size.  A zero size may mean that the
                     symbol isn't an object or function (e.g. a
                     label), or it may just mean that the size was not
                     specified.  */
                  if (MSYMBOL_SIZE (&msymbol[hi]) == 0
                      && best_zero_sized == -1)
                    {
                      best_zero_sized = hi;
                      hi--;
                      continue;
                    }

                  /* If we are past the end of the current symbol, try
                     the previous symbol if it has a larger overlapping
                     size.  This happens on i686-pc-linux-gnu with glibc;
                     the nocancel variants of system calls are inside
                     the cancellable variants, but both have sizes.  */
                  if (hi > 0
                      && MSYMBOL_SIZE (&msymbol[hi]) != 0
                      && pc >= (SYMBOL_VALUE_ADDRESS (&msymbol[hi])
                                + MSYMBOL_SIZE (&msymbol[hi]))
                      && pc < (SYMBOL_VALUE_ADDRESS (&msymbol[hi - 1])
                               + MSYMBOL_SIZE (&msymbol[hi - 1])))
                    {
                      hi--;
                      continue;
                    }

                  /* Otherwise, this symbol must be as good as we're going
                     to get.  */
                  break;
                }

              /* If HI has a zero size, and best_zero_sized is set,
                 then we had two or more zero-sized symbols; prefer
                 the first one we found (which may have a higher
                 address).  Also, if we ran off the end, be sure
                 to back up.  */
              if (best_zero_sized != -1
                  && (hi < 0 || MSYMBOL_SIZE (&msymbol[hi]) == 0))
                hi = best_zero_sized;

              /* If the minimal symbol has a non-zero size, and this
                 PC appears to be outside the symbol's contents, then
                 refuse to use this symbol.  If we found a zero-sized
                 symbol with an address greater than this symbol's,
                 use that instead.  We assume that if symbols have
                 specified sizes, they do not overlap.  */

              if (hi >= 0
                  && MSYMBOL_SIZE (&msymbol[hi]) != 0
                  && pc >= (SYMBOL_VALUE_ADDRESS (&msymbol[hi])
                            + MSYMBOL_SIZE (&msymbol[hi])))
                {
                  if (best_zero_sized != -1)
                    hi = best_zero_sized;
                  else
                    /* Go on to the next object file.  */
                    continue;
                }

              /* The minimal symbol indexed by hi now is the best one in this
                 objfile's minimal symbol table.  See if it is the best one
                 overall. */

              if (hi >= 0
                  && ((best_symbol == NULL) ||
                      (SYMBOL_VALUE_ADDRESS (best_symbol) <
                       SYMBOL_VALUE_ADDRESS (&msymbol[hi]))))
                {
                  best_symbol = &msymbol[hi];
                }
            }
        }
    }
  return (best_symbol);
}

/* Backward compatibility: search through the minimal symbol table 
   for a matching PC (no section given) */

struct minimal_symbol *
lookup_minimal_symbol_by_pc (CORE_ADDR pc)
{
  /* NOTE: cagney/2004-01-27: This was using find_pc_mapped_section to
     force the section but that (well unless you're doing overlay
     debugging) always returns NULL making the call somewhat useless.  */
  struct obj_section *section = find_pc_section (pc);
  if (section == NULL)
    return NULL;
  return lookup_minimal_symbol_by_pc_section (pc, section->the_bfd_section);
}
\f

/* Return leading symbol character for a BFD. If BFD is NULL,
   return the leading symbol character from the main objfile.  */

static int get_symbol_leading_char (bfd *);

static int
get_symbol_leading_char (bfd *abfd)
{
  if (abfd != NULL)
    return bfd_get_symbol_leading_char (abfd);
  if (symfile_objfile != NULL && symfile_objfile->obfd != NULL)
    return bfd_get_symbol_leading_char (symfile_objfile->obfd);
  return 0;
}

/* Prepare to start collecting minimal symbols.  Note that presetting
   msym_bunch_index to BUNCH_SIZE causes the first call to save a minimal
   symbol to allocate the memory for the first bunch. */

void
init_minimal_symbol_collection (void)
{
  msym_count = 0;
  msym_bunch = NULL;
  msym_bunch_index = BUNCH_SIZE;
}

void
prim_record_minimal_symbol (const char *name, CORE_ADDR address,
                            enum minimal_symbol_type ms_type,
                            struct objfile *objfile)
{
  int section;

  switch (ms_type)
    {
    case mst_text:
    case mst_file_text:
    case mst_solib_trampoline:
      section = SECT_OFF_TEXT (objfile);
      break;
    case mst_data:
    case mst_file_data:
      section = SECT_OFF_DATA (objfile);
      break;
    case mst_bss:
    case mst_file_bss:
      section = SECT_OFF_BSS (objfile);
      break;
    default:
      section = -1;
    }

  prim_record_minimal_symbol_and_info (name, address, ms_type,
                                       NULL, section, NULL, objfile);
}

/* Record a minimal symbol in the msym bunches.  Returns the symbol
   newly created.  */

struct minimal_symbol *
prim_record_minimal_symbol_and_info (const char *name, CORE_ADDR address,
                                     enum minimal_symbol_type ms_type,
                                     char *info, int section,
                                     asection *bfd_section,
                                     struct objfile *objfile)
{
  struct msym_bunch *new;
  struct minimal_symbol *msymbol;

  /* Don't put gcc_compiled, __gnu_compiled_cplus, and friends into
     the minimal symbols, because if there is also another symbol
     at the same address (e.g. the first function of the file),
     lookup_minimal_symbol_by_pc would have no way of getting the
     right one.  */
  if (ms_type == mst_file_text && name[0] == 'g'
      && (strcmp (name, GCC_COMPILED_FLAG_SYMBOL) == 0
          || strcmp (name, GCC2_COMPILED_FLAG_SYMBOL) == 0))
    return (NULL);

  /* It's safe to strip the leading char here once, since the name
     is also stored stripped in the minimal symbol table. */
  if (name[0] == get_symbol_leading_char (objfile->obfd))
    ++name;

  if (ms_type == mst_file_text && strncmp (name, "__gnu_compiled", 14) == 0)
    return (NULL);

  if (msym_bunch_index == BUNCH_SIZE)
    {
      new = (struct msym_bunch *) xmalloc (sizeof (struct msym_bunch));
      msym_bunch_index = 0;
      new->next = msym_bunch;
      msym_bunch = new;
    }
  msymbol = &msym_bunch->contents[msym_bunch_index];
  SYMBOL_INIT_LANGUAGE_SPECIFIC (msymbol, language_unknown);
  SYMBOL_LANGUAGE (msymbol) = language_auto;
  SYMBOL_SET_NAMES (msymbol, (char *)name, strlen (name), objfile);

  SYMBOL_VALUE_ADDRESS (msymbol) = address;
  SYMBOL_SECTION (msymbol) = section;
  SYMBOL_BFD_SECTION (msymbol) = bfd_section;

  MSYMBOL_TYPE (msymbol) = ms_type;
  /* FIXME:  This info, if it remains, needs its own field.  */
  MSYMBOL_INFO (msymbol) = info;        /* FIXME! */
  MSYMBOL_SIZE (msymbol) = 0;

  /* The hash pointers must be cleared! If they're not,
     add_minsym_to_hash_table will NOT add this msymbol to the hash table. */
  msymbol->hash_next = NULL;
  msymbol->demangled_hash_next = NULL;

  msym_bunch_index++;
  msym_count++;
  OBJSTAT (objfile, n_minsyms++);
  return msymbol;
}

/* Compare two minimal symbols by address and return a signed result based
   on unsigned comparisons, so that we sort into unsigned numeric order.  
   Within groups with the same address, sort by name.  */

static int
compare_minimal_symbols (const void *fn1p, const void *fn2p)
{
  const struct minimal_symbol *fn1;
  const struct minimal_symbol *fn2;

  fn1 = (const struct minimal_symbol *) fn1p;
  fn2 = (const struct minimal_symbol *) fn2p;

  if (SYMBOL_VALUE_ADDRESS (fn1) < SYMBOL_VALUE_ADDRESS (fn2))
    {
      return (-1);              /* addr 1 is less than addr 2 */
    }
  else if (SYMBOL_VALUE_ADDRESS (fn1) > SYMBOL_VALUE_ADDRESS (fn2))
    {
      return (1);               /* addr 1 is greater than addr 2 */
    }
  else
    /* addrs are equal: sort by name */
    {
      char *name1 = SYMBOL_LINKAGE_NAME (fn1);
      char *name2 = SYMBOL_LINKAGE_NAME (fn2);

      if (name1 && name2)       /* both have names */
        return strcmp (name1, name2);
      else if (name2)
        return 1;               /* fn1 has no name, so it is "less" */
      else if (name1)           /* fn2 has no name, so it is "less" */
        return -1;
      else
        return (0);             /* neither has a name, so they're equal. */
    }
}

/* Discard the currently collected minimal symbols, if any.  If we wish
   to save them for later use, we must have already copied them somewhere
   else before calling this function.

   FIXME:  We could allocate the minimal symbol bunches on their own
   obstack and then simply blow the obstack away when we are done with
   it.  Is it worth the extra trouble though? */

static void
do_discard_minimal_symbols_cleanup (void *arg)
{
  struct msym_bunch *next;

  while (msym_bunch != NULL)
    {
      next = msym_bunch->next;
      xfree (msym_bunch);
      msym_bunch = next;
    }
}

struct cleanup *
make_cleanup_discard_minimal_symbols (void)
{
  return make_cleanup (do_discard_minimal_symbols_cleanup, 0);
}



/* Compact duplicate entries out of a minimal symbol table by walking
   through the table and compacting out entries with duplicate addresses
   and matching names.  Return the number of entries remaining.

   On entry, the table resides between msymbol[0] and msymbol[mcount].
   On exit, it resides between msymbol[0] and msymbol[result_count].

   When files contain multiple sources of symbol information, it is
   possible for the minimal symbol table to contain many duplicate entries.
   As an example, SVR4 systems use ELF formatted object files, which
   usually contain at least two different types of symbol tables (a
   standard ELF one and a smaller dynamic linking table), as well as
   DWARF debugging information for files compiled with -g.

   Without compacting, the minimal symbol table for gdb itself contains
   over a 1000 duplicates, about a third of the total table size.  Aside
   from the potential trap of not noticing that two successive entries
   identify the same location, this duplication impacts the time required
   to linearly scan the table, which is done in a number of places.  So we
   just do one linear scan here and toss out the duplicates.

   Note that we are not concerned here about recovering the space that
   is potentially freed up, because the strings themselves are allocated
   on the objfile_obstack, and will get automatically freed when the symbol
   table is freed.  The caller can free up the unused minimal symbols at
   the end of the compacted region if their allocation strategy allows it.

   Also note we only go up to the next to last entry within the loop
   and then copy the last entry explicitly after the loop terminates.

   Since the different sources of information for each symbol may
   have different levels of "completeness", we may have duplicates
   that have one entry with type "mst_unknown" and the other with a
   known type.  So if the one we are leaving alone has type mst_unknown,
   overwrite its type with the type from the one we are compacting out.  */

static int
compact_minimal_symbols (struct minimal_symbol *msymbol, int mcount,
                         struct objfile *objfile)
{
  struct minimal_symbol *copyfrom;
  struct minimal_symbol *copyto;

  if (mcount > 0)
    {
      copyfrom = copyto = msymbol;
      while (copyfrom < msymbol + mcount - 1)
        {
          if (SYMBOL_VALUE_ADDRESS (copyfrom)
              == SYMBOL_VALUE_ADDRESS ((copyfrom + 1))
              && strcmp (SYMBOL_LINKAGE_NAME (copyfrom),
                         SYMBOL_LINKAGE_NAME ((copyfrom + 1))) == 0)
            {
              if (MSYMBOL_TYPE ((copyfrom + 1)) == mst_unknown)
                {
                  MSYMBOL_TYPE ((copyfrom + 1)) = MSYMBOL_TYPE (copyfrom);
                }
              copyfrom++;
            }
          else
            *copyto++ = *copyfrom++;
        }
      *copyto++ = *copyfrom++;
      mcount = copyto - msymbol;
    }
  return (mcount);
}

/* Build (or rebuild) the minimal symbol hash tables.  This is necessary
   after compacting or sorting the table since the entries move around
   thus causing the internal minimal_symbol pointers to become jumbled. */
  
static void
build_minimal_symbol_hash_tables (struct objfile *objfile)
{
  int i;
  struct minimal_symbol *msym;

  /* Clear the hash tables. */
  for (i = 0; i < MINIMAL_SYMBOL_HASH_SIZE; i++)
    {
      objfile->msymbol_hash[i] = 0;
      objfile->msymbol_demangled_hash[i] = 0;
    }

  /* Now, (re)insert the actual entries. */
  for (i = objfile->minimal_symbol_count, msym = objfile->msymbols;
       i > 0;
       i--, msym++)
    {
      msym->hash_next = 0;
      add_minsym_to_hash_table (msym, objfile->msymbol_hash);

      msym->demangled_hash_next = 0;
      if (SYMBOL_SEARCH_NAME (msym) != SYMBOL_LINKAGE_NAME (msym))
        add_minsym_to_demangled_hash_table (msym,
                                            objfile->msymbol_demangled_hash);
    }
}

/* Add the minimal symbols in the existing bunches to the objfile's official
   minimal symbol table.  In most cases there is no minimal symbol table yet
   for this objfile, and the existing bunches are used to create one.  Once
   in a while (for shared libraries for example), we add symbols (e.g. common
   symbols) to an existing objfile.

   Because of the way minimal symbols are collected, we generally have no way
   of knowing what source language applies to any particular minimal symbol.
   Specifically, we have no way of knowing if the minimal symbol comes from a
   C++ compilation unit or not.  So for the sake of supporting cached
   demangled C++ names, we have no choice but to try and demangle each new one
   that comes in.  If the demangling succeeds, then we assume it is a C++
   symbol and set the symbol's language and demangled name fields
   appropriately.  Note that in order to avoid unnecessary demanglings, and
   allocating obstack space that subsequently can't be freed for the demangled
   names, we mark all newly added symbols with language_auto.  After
   compaction of the minimal symbols, we go back and scan the entire minimal
   symbol table looking for these new symbols.  For each new symbol we attempt
   to demangle it, and if successful, record it as a language_cplus symbol
   and cache the demangled form on the symbol obstack.  Symbols which don't
   demangle are marked as language_unknown symbols, which inhibits future
   attempts to demangle them if we later add more minimal symbols. */

void
install_minimal_symbols (struct objfile *objfile)
{
  int bindex;
  int mcount;
  struct msym_bunch *bunch;
  struct minimal_symbol *msymbols;
  int alloc_count;

  if (msym_count > 0)
    {
      /* Allocate enough space in the obstack, into which we will gather the
         bunches of new and existing minimal symbols, sort them, and then
         compact out the duplicate entries.  Once we have a final table,
         we will give back the excess space.  */

      alloc_count = msym_count + objfile->minimal_symbol_count + 1;
      obstack_blank (&objfile->objfile_obstack,
                     alloc_count * sizeof (struct minimal_symbol));
      msymbols = (struct minimal_symbol *)
        obstack_base (&objfile->objfile_obstack);

      /* Copy in the existing minimal symbols, if there are any.  */

      if (objfile->minimal_symbol_count)
        memcpy ((char *) msymbols, (char *) objfile->msymbols,
            objfile->minimal_symbol_count * sizeof (struct minimal_symbol));

      /* Walk through the list of minimal symbol bunches, adding each symbol
         to the new contiguous array of symbols.  Note that we start with the
         current, possibly partially filled bunch (thus we use the current
         msym_bunch_index for the first bunch we copy over), and thereafter
         each bunch is full. */

      mcount = objfile->minimal_symbol_count;

      for (bunch = msym_bunch; bunch != NULL; bunch = bunch->next)
        {
          for (bindex = 0; bindex < msym_bunch_index; bindex++, mcount++)
            msymbols[mcount] = bunch->contents[bindex];
          msym_bunch_index = BUNCH_SIZE;
        }

      /* Sort the minimal symbols by address.  */

      qsort (msymbols, mcount, sizeof (struct minimal_symbol),
             compare_minimal_symbols);

      /* Compact out any duplicates, and free up whatever space we are
         no longer using.  */

      mcount = compact_minimal_symbols (msymbols, mcount, objfile);

      obstack_blank (&objfile->objfile_obstack,
               (mcount + 1 - alloc_count) * sizeof (struct minimal_symbol));
      msymbols = (struct minimal_symbol *)
        obstack_finish (&objfile->objfile_obstack);

      /* We also terminate the minimal symbol table with a "null symbol",
         which is *not* included in the size of the table.  This makes it
         easier to find the end of the table when we are handed a pointer
         to some symbol in the middle of it.  Zero out the fields in the
         "null symbol" allocated at the end of the array.  Note that the
         symbol count does *not* include this null symbol, which is why it
         is indexed by mcount and not mcount-1. */

      SYMBOL_LINKAGE_NAME (&msymbols[mcount]) = NULL;
      SYMBOL_VALUE_ADDRESS (&msymbols[mcount]) = 0;
      MSYMBOL_INFO (&msymbols[mcount]) = NULL;
      MSYMBOL_SIZE (&msymbols[mcount]) = 0;
      MSYMBOL_TYPE (&msymbols[mcount]) = mst_unknown;
      SYMBOL_INIT_LANGUAGE_SPECIFIC (&msymbols[mcount], language_unknown);

      /* Attach the minimal symbol table to the specified objfile.
         The strings themselves are also located in the objfile_obstack
         of this objfile.  */

      objfile->minimal_symbol_count = mcount;
      objfile->msymbols = msymbols;

      /* Try to guess the appropriate C++ ABI by looking at the names 
         of the minimal symbols in the table.  */
      {
        int i;

        for (i = 0; i < mcount; i++)
          {
            /* If a symbol's name starts with _Z and was successfully
               demangled, then we can assume we've found a GNU v3 symbol.
               For now we set the C++ ABI globally; if the user is
               mixing ABIs then the user will need to "set cp-abi"
               manually.  */
            const char *name = SYMBOL_LINKAGE_NAME (&objfile->msymbols[i]);
            if (name[0] == '_' && name[1] == 'Z'
                && SYMBOL_DEMANGLED_NAME (&objfile->msymbols[i]) != NULL)
              {
                set_cp_abi_as_auto_default ("gnu-v3");
                break;
              }
          }
      }

      /* Now build the hash tables; we can't do this incrementally
         at an earlier point since we weren't finished with the obstack
         yet.  (And if the msymbol obstack gets moved, all the internal
         pointers to other msymbols need to be adjusted.) */
      build_minimal_symbol_hash_tables (objfile);
    }
}

/* Sort all the minimal symbols in OBJFILE.  */

void
msymbols_sort (struct objfile *objfile)
{
  qsort (objfile->msymbols, objfile->minimal_symbol_count,
         sizeof (struct minimal_symbol), compare_minimal_symbols);
  build_minimal_symbol_hash_tables (objfile);
}

/* Check if PC is in a shared library trampoline code stub.
   Return minimal symbol for the trampoline entry or NULL if PC is not
   in a trampoline code stub.  */

struct minimal_symbol *
lookup_solib_trampoline_symbol_by_pc (CORE_ADDR pc)
{
  struct minimal_symbol *msymbol = lookup_minimal_symbol_by_pc (pc);

  if (msymbol != NULL && MSYMBOL_TYPE (msymbol) == mst_solib_trampoline)
    return msymbol;
  return NULL;
}

/* If PC is in a shared library trampoline code stub, return the
   address of the `real' function belonging to the stub.
   Return 0 if PC is not in a trampoline code stub or if the real
   function is not found in the minimal symbol table.

   We may fail to find the right function if a function with the
   same name is defined in more than one shared library, but this
   is considered bad programming style. We could return 0 if we find
   a duplicate function in case this matters someday.  */

CORE_ADDR
find_solib_trampoline_target (struct frame_info *frame, CORE_ADDR pc)
{
  struct objfile *objfile;
  struct minimal_symbol *msymbol;
  struct minimal_symbol *tsymbol = lookup_solib_trampoline_symbol_by_pc (pc);

  if (tsymbol != NULL)
    {
      ALL_MSYMBOLS (objfile, msymbol)
      {
        if (MSYMBOL_TYPE (msymbol) == mst_text
            && strcmp (SYMBOL_LINKAGE_NAME (msymbol),
                       SYMBOL_LINKAGE_NAME (tsymbol)) == 0)
          return SYMBOL_VALUE_ADDRESS (msymbol);
      }
    }
  return 0;
}