xref: /third_party/elfutils/libdw/dwarf_getscopevar.c

/* Find a named variable or parameter within given scopes.
   Copyright (C) 2005-2009 Red Hat, Inc.
   This file is part of elfutils.

   This file is free software; you can redistribute it and/or modify
   it under the terms of either

     * the GNU Lesser General Public License as published by the Free
       Software Foundation; either version 3 of the License, or (at
       your option) any later version

   or

     * 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

   or both in parallel, as here.

   elfutils 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 copies of the GNU General Public License and
   the GNU Lesser General Public License along with this program.  If
   not, see <http://www.gnu.org/licenses/>.  */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <stdbool.h>
#include <string.h>
#include "libdwP.h"
#include <dwarf.h>


/* Find the containing CU's files.  */
static int
getfiles (Dwarf_Die *die, Dwarf_Files **files)
{
  return INTUSE(dwarf_getsrcfiles) (&CUDIE (die->cu), files, NULL);
}

/* Fetch an attribute that should have a constant integer form.  */
static int
getattr (Dwarf_Die *die, int search_name, Dwarf_Word *value)
{
  Dwarf_Attribute attr_mem;
  return INTUSE(dwarf_formudata) (INTUSE(dwarf_attr) (die, search_name,
						      &attr_mem), value);
}

static inline int
file_matches (const char *lastfile,
              size_t match_file_len, const char *match_file,
              Dwarf_Files *files, size_t idx,
              bool *lastfile_matches)
{
  if (idx >= files->nfiles)
    return false;
  const char *file = files->info[idx].name;
  if (file != lastfile)
    {
      size_t len = strlen (file);
      *lastfile_matches = (len >= match_file_len
                          && !memcmp (match_file, file, match_file_len)
                          && (len == match_file_len
                              || file[len - match_file_len - 1] == '/'));
    }
  return *lastfile_matches;
}

/* Search SCOPES[0..NSCOPES-1] for a variable called NAME.
   Ignore the first SKIP_SHADOWS scopes that match the name.
   If MATCH_FILE is not null, accept only declaration in that source file;
   if MATCH_LINENO or MATCH_LINECOL are also nonzero, accept only declaration
   at that line and column.

   If successful, fill in *RESULT with the DIE of the variable found,
   and return N where SCOPES[N] is the scope defining the variable.
   Return -1 for errors or -2 for no matching variable found.  */

int
dwarf_getscopevar (Dwarf_Die *scopes, int nscopes,
		   const char *name, int skip_shadows,
		   const char *match_file, int match_lineno, int match_linecol,
		   Dwarf_Die *result)
{
  /* Match against the given file name.  */
  size_t match_file_len = match_file == NULL ? 0 : strlen (match_file);
  bool lastfile_matches = false;
  const char *lastfile = NULL;

  /* Start with the innermost scope and move out.  */
  for (int out = 0; out < nscopes; ++out)
    if (INTUSE(dwarf_haschildren) (&scopes[out]))
      {
	if (INTUSE(dwarf_child) (&scopes[out], result) != 0)
	  return -1;
	do
	  {
	    switch (INTUSE(dwarf_tag) (result))
	      {
	      case DW_TAG_variable:
	      case DW_TAG_formal_parameter:
		break;

	      default:
		continue;
	      }

	    /* Only get here for a variable or parameter.  Check the name.  */
	    const char *diename = INTUSE(dwarf_diename) (result);
	    if (diename != NULL && !strcmp (name, diename))
	      {
		/* We have a matching name.  */

		if (skip_shadows > 0)
		  {
		    /* Punt this scope for the one it shadows.  */
		    --skip_shadows;
		    break;
		  }

		if (match_file != NULL)
		  {
		    /* Check its decl_file.  */

		    Dwarf_Word i;
		    Dwarf_Files *files;
		    if (getattr (result, DW_AT_decl_file, &i) != 0
			|| getfiles (&scopes[out], &files) != 0)
		      break;

		    if (!file_matches (lastfile, match_file_len, match_file,
		                       files, i, &lastfile_matches))
		      break;

		    if (match_lineno > 0
			&& (getattr (result, DW_AT_decl_line, &i) != 0
			    || (int) i != match_lineno))
		      break;
		    if (match_linecol > 0
			&& (getattr (result, DW_AT_decl_column, &i) != 0
			    || (int) i != match_linecol))
		      break;
		  }

		/* We have a winner!  */
		return out;
	      }
	  }
	while (INTUSE(dwarf_siblingof) (result, result) == 0);
      }

  return -2;
}