Constify some linespec functions

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

/* Data structures and API for event locations in GDB.
   Copyright (C) 2013-2017 Free Software Foundation, Inc.

   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 3 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, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"
#include "gdb_assert.h"
#include "location.h"
#include "symtab.h"
#include "language.h"
#include "linespec.h"
#include "cli/cli-utils.h"
#include "probe.h"
#include "cp-support.h"

#include <ctype.h>
#include <string.h>

/* An event location used to set a stop event in the inferior.
   This structure is an amalgam of the various ways
   to specify where a stop event should be set.  */

struct event_location
{
  /* The type of this breakpoint specification.  */
  enum event_location_type type;
#define EL_TYPE(P) (P)->type

  union
  {
    /* A generic "this is a string specification" for a location.
       This representation is used by both "normal" linespecs and
       probes.  */
    char *addr_string;
#define EL_LINESPEC(P) ((P)->u.addr_string)
#define EL_PROBE(P) ((P)->u.addr_string)

    /* An address in the inferior.  */
    CORE_ADDR address;
#define EL_ADDRESS(P) (P)->u.address

    /* An explicit location.  */
    struct explicit_location explicit_loc;
#define EL_EXPLICIT(P) (&((P)->u.explicit_loc))
  } u;

  /* Cached string representation of this location.  This is used, e.g., to
     save stop event locations to file.  Malloc'd.  */
  char *as_string;
#define EL_STRING(P) ((P)->as_string)
};

/* See description in location.h.  */

enum event_location_type
event_location_type (const struct event_location *location)
{
  return EL_TYPE (location);
}

/* See description in location.h.  */

void
initialize_explicit_location (struct explicit_location *explicit_loc)
{
  memset (explicit_loc, 0, sizeof (struct explicit_location));
  explicit_loc->line_offset.sign = LINE_OFFSET_UNKNOWN;
}

/* See description in location.h.  */

event_location_up
new_linespec_location (const char **linespec)
{
  struct event_location *location;

  location = XCNEW (struct event_location);
  EL_TYPE (location) = LINESPEC_LOCATION;
  if (*linespec != NULL)
    {
      const char *p;
      const char *orig = *linespec;

      linespec_lex_to_end (linespec);
      p = remove_trailing_whitespace (orig, *linespec);
      if ((p - orig) > 0)
        EL_LINESPEC (location) = savestring (orig, p - orig);
    }
  return event_location_up (location);
}

/* See description in location.h.  */

const char *
get_linespec_location (const struct event_location *location)
{
  gdb_assert (EL_TYPE (location) == LINESPEC_LOCATION);
  return EL_LINESPEC (location);
}

/* See description in location.h.  */

event_location_up
new_address_location (CORE_ADDR addr, const char *addr_string,
                      int addr_string_len)
{
  struct event_location *location;

  location = XCNEW (struct event_location);
  EL_TYPE (location) = ADDRESS_LOCATION;
  EL_ADDRESS (location) = addr;
  if (addr_string != NULL)
    EL_STRING (location) = xstrndup (addr_string, addr_string_len);
  return event_location_up (location);
}

/* See description in location.h.  */

CORE_ADDR
get_address_location (const struct event_location *location)
{
  gdb_assert (EL_TYPE (location) == ADDRESS_LOCATION);
  return EL_ADDRESS (location);
}

/* See description in location.h.  */

const char *
get_address_string_location (const struct event_location *location)
{
  gdb_assert (EL_TYPE (location) == ADDRESS_LOCATION);
  return EL_STRING (location);
}

/* See description in location.h.  */

event_location_up
new_probe_location (const char *probe)
{
  struct event_location *location;

  location = XCNEW (struct event_location);
  EL_TYPE (location) = PROBE_LOCATION;
  if (probe != NULL)
    EL_PROBE (location) = xstrdup (probe);
  return event_location_up (location);
}

/* See description in location.h.  */

const char *
get_probe_location (const struct event_location *location)
{
  gdb_assert (EL_TYPE (location) == PROBE_LOCATION);
  return EL_PROBE (location);
}

/* See description in location.h.  */

event_location_up
new_explicit_location (const struct explicit_location *explicit_loc)
{
  struct event_location tmp;

  memset (&tmp, 0, sizeof (struct event_location));
  EL_TYPE (&tmp) = EXPLICIT_LOCATION;
  initialize_explicit_location (EL_EXPLICIT (&tmp));
  if (explicit_loc != NULL)
    {
      if (explicit_loc->source_filename != NULL)
        {
          EL_EXPLICIT (&tmp)->source_filename
            = explicit_loc->source_filename;
        }

      if (explicit_loc->function_name != NULL)
        EL_EXPLICIT (&tmp)->function_name
          = explicit_loc->function_name;

      if (explicit_loc->label_name != NULL)
        EL_EXPLICIT (&tmp)->label_name = explicit_loc->label_name;

      if (explicit_loc->line_offset.sign != LINE_OFFSET_UNKNOWN)
        EL_EXPLICIT (&tmp)->line_offset = explicit_loc->line_offset;
    }

  return copy_event_location (&tmp);
}

/* See description in location.h.  */

struct explicit_location *
get_explicit_location (struct event_location *location)
{
  gdb_assert (EL_TYPE (location) == EXPLICIT_LOCATION);
  return EL_EXPLICIT (location);
}

/* See description in location.h.  */

const struct explicit_location *
get_explicit_location_const (const struct event_location *location)
{
  gdb_assert (EL_TYPE (location) == EXPLICIT_LOCATION);
  return EL_EXPLICIT (location);
}

/* This convenience function returns a malloc'd string which
   represents the location in EXPLICIT_LOC.

   AS_LINESPEC is non-zero if this string should be a linespec.
   Otherwise it will be output in explicit form.  */

static char *
explicit_to_string_internal (int as_linespec,
                             const struct explicit_location *explicit_loc)
{
  int need_space = 0;
  char space = as_linespec ? ':' : ' ';
  string_file buf;

  if (explicit_loc->source_filename != NULL)
    {
      if (!as_linespec)
        buf.puts ("-source ");
      buf.puts (explicit_loc->source_filename);
      need_space = 1;
    }

  if (explicit_loc->function_name != NULL)
    {
      if (need_space)
        buf.putc (space);
      if (!as_linespec)
        buf.puts ("-function ");
      buf.puts (explicit_loc->function_name);
      need_space = 1;
    }

  if (explicit_loc->label_name != NULL)
    {
      if (need_space)
        buf.putc (space);
      if (!as_linespec)
        buf.puts ("-label ");
      buf.puts (explicit_loc->label_name);
      need_space = 1;
    }

  if (explicit_loc->line_offset.sign != LINE_OFFSET_UNKNOWN)
    {
      if (need_space)
        buf.putc (space);
      if (!as_linespec)
        buf.puts ("-line ");
      buf.printf ("%s%d",
                  (explicit_loc->line_offset.sign == LINE_OFFSET_NONE ? ""
                   : (explicit_loc->line_offset.sign
                      == LINE_OFFSET_PLUS ? "+" : "-")),
                  explicit_loc->line_offset.offset);
    }

  return xstrdup (buf.c_str ());
}

/* See description in location.h.  */

char *
explicit_location_to_string (const struct explicit_location *explicit_loc)
{
  return explicit_to_string_internal (0, explicit_loc);
}

/* See description in location.h.  */

char *
explicit_location_to_linespec (const struct explicit_location *explicit_loc)
{
  return explicit_to_string_internal (1, explicit_loc);
}

/* See description in location.h.  */

event_location_up
copy_event_location (const struct event_location *src)
{
  struct event_location *dst;

  dst = XCNEW (struct event_location);
  EL_TYPE (dst) = EL_TYPE (src);
  if (EL_STRING (src) != NULL)
    EL_STRING (dst) = xstrdup (EL_STRING (src));

  switch (EL_TYPE (src))
    {
    case LINESPEC_LOCATION:
      if (EL_LINESPEC (src) != NULL)
        EL_LINESPEC (dst) = xstrdup (EL_LINESPEC (src));
      break;

    case ADDRESS_LOCATION:
      EL_ADDRESS (dst) = EL_ADDRESS (src);
      break;

    case EXPLICIT_LOCATION:
      if (EL_EXPLICIT (src)->source_filename != NULL)
        EL_EXPLICIT (dst)->source_filename
          = xstrdup (EL_EXPLICIT (src)->source_filename);

      if (EL_EXPLICIT (src)->function_name != NULL)
        EL_EXPLICIT (dst)->function_name
          = xstrdup (EL_EXPLICIT (src)->function_name);

      if (EL_EXPLICIT (src)->label_name != NULL)
        EL_EXPLICIT (dst)->label_name = xstrdup (EL_EXPLICIT (src)->label_name);

      EL_EXPLICIT (dst)->line_offset = EL_EXPLICIT (src)->line_offset;
      break;


    case PROBE_LOCATION:
      if (EL_PROBE (src) != NULL)
        EL_PROBE (dst) = xstrdup (EL_PROBE (src));
      break;

    default:
      gdb_assert_not_reached ("unknown event location type");
    }

  return event_location_up (dst);
}

void
event_location_deleter::operator() (event_location *location) const
{
  if (location != NULL)
    {
      xfree (EL_STRING (location));

      switch (EL_TYPE (location))
        {
        case LINESPEC_LOCATION:
          xfree (EL_LINESPEC (location));
          break;

        case ADDRESS_LOCATION:
          /* Nothing to do.  */
          break;

        case EXPLICIT_LOCATION:
          xfree (EL_EXPLICIT (location)->source_filename);
          xfree (EL_EXPLICIT (location)->function_name);
          xfree (EL_EXPLICIT (location)->label_name);
          break;

        case PROBE_LOCATION:
          xfree (EL_PROBE (location));
          break;

        default:
          gdb_assert_not_reached ("unknown event location type");
        }

      xfree (location);
    }
}

/* See description in location.h.  */

const char *
event_location_to_string (struct event_location *location)
{
  if (EL_STRING (location) == NULL)
    {
      switch (EL_TYPE (location))
        {
        case LINESPEC_LOCATION:
          if (EL_LINESPEC (location) != NULL)
            EL_STRING (location) = xstrdup (EL_LINESPEC (location));
          break;

        case ADDRESS_LOCATION:
          EL_STRING (location)
            = xstrprintf ("*%s",
                          core_addr_to_string (EL_ADDRESS (location)));
          break;

        case EXPLICIT_LOCATION:
          EL_STRING (location)
            = explicit_location_to_string (EL_EXPLICIT (location));
          break;

        case PROBE_LOCATION:
          EL_STRING (location) = xstrdup (EL_PROBE (location));
          break;

        default:
          gdb_assert_not_reached ("unknown event location type");
        }
    }

  return EL_STRING (location);
}

/* Find an instance of the quote character C in the string S that is
   outside of all single- and double-quoted strings (i.e., any quoting
   other than C).  */

static const char *
find_end_quote (const char *s, char end_quote_char)
{
  /* zero if we're not in quotes;
     '"' if we're in a double-quoted string;
     '\'' if we're in a single-quoted string.  */
  char nested_quote_char = '\0';

  for (const char *scan = s; *scan != '\0'; scan++)
    {
      if (nested_quote_char != '\0')
        {
          if (*scan == nested_quote_char)
            nested_quote_char = '\0';
          else if (scan[0] == '\\' && *(scan + 1) != '\0')
            scan++;
        }
      else if (*scan == end_quote_char && nested_quote_char == '\0')
        return scan;
      else if (*scan == '"' || *scan == '\'')
        nested_quote_char = *scan;
    }

  return 0;
}

/* A lexer for explicit locations.  This function will advance INP
   past any strings that it lexes.  Returns a malloc'd copy of the
   lexed string or NULL if no lexing was done.  */

static gdb::unique_xmalloc_ptr<char>
explicit_location_lex_one (const char **inp,
                           const struct language_defn *language,
                           explicit_completion_info *completion_info)
{
  const char *start = *inp;

  if (*start == '\0')
    return NULL;

  /* If quoted, skip to the ending quote.  */
  if (strchr (get_gdb_linespec_parser_quote_characters (), *start))
    {
      if (completion_info != NULL)
        completion_info->quoted_arg_start = start;

      const char *end = find_end_quote (start + 1, *start);

      if (end == NULL)
        {
          if (completion_info == NULL)
            error (_("Unmatched quote, %s."), start);

          end = start + strlen (start);
          *inp = end;
          return gdb::unique_xmalloc_ptr<char> (savestring (start + 1,
                                                            *inp - start - 1));
        }

      if (completion_info != NULL)
        completion_info->quoted_arg_end = end;
      *inp = end + 1;
      return gdb::unique_xmalloc_ptr<char> (savestring (start + 1,
                                                        *inp - start - 2));
    }

  /* If the input starts with '-' or '+', the string ends with the next
     whitespace or comma.  */
  if (*start == '-' || *start == '+')
    {
      while (*inp[0] != '\0' && *inp[0] != ',' && !isspace (*inp[0]))
        ++(*inp);
    }
  else
    {
      /* Handle numbers first, stopping at the next whitespace or ','.  */
      while (isdigit (*inp[0]))
        ++(*inp);
      if (*inp[0] == '\0' || isspace (*inp[0]) || *inp[0] == ',')
        return gdb::unique_xmalloc_ptr<char> (savestring (start,
                                                          *inp - start));

      /* Otherwise stop at the next occurrence of whitespace, '\0',
         keyword, or ','.  */
      *inp = start;
      while ((*inp)[0]
             && (*inp)[0] != ','
             && !(isspace ((*inp)[0])
                  || linespec_lexer_lex_keyword (&(*inp)[1])))
        {
          /* Special case: C++ operator,.  */
          if (language->la_language == language_cplus
              && startswith (*inp, CP_OPERATOR_STR))
            (*inp) += CP_OPERATOR_LEN;
          ++(*inp);
        }
    }

  if (*inp - start > 0)
    return gdb::unique_xmalloc_ptr<char> (savestring (start, *inp - start));

  return NULL;
}

/* Return true if COMMA points past "operator".  START is the start of
   the line that COMMAND points to, hence when reading backwards, we
   must not read any character before START.  */

static bool
is_cp_operator (const char *start, const char *comma)
{
  if (comma != NULL
      && (comma - start) >= CP_OPERATOR_LEN)
    {
      const char *p = comma;

      while (p > start && isspace (p[-1]))
        p--;
      if (p - start >= CP_OPERATOR_LEN)
        {
          p -= CP_OPERATOR_LEN;
          if (strncmp (p, CP_OPERATOR_STR, CP_OPERATOR_LEN) == 0
              && (p == start
                  || !(isalnum (p[-1]) || p[-1] == '_')))
            {
              return true;
            }
        }
    }
  return false;
}

/* When scanning the input string looking for the next explicit
   location option/delimiter, we jump to the next option by looking
   for ",", and "-".  Such a character can also appear in C++ symbols
   like "operator," and "operator-".  So when we find such a
   character, we call this function to check if we found such a
   symbol, meaning we had a false positive for an option string.  In
   that case, we keep looking for the next delimiter, until we find
   one that is not a false positive, or we reach end of string.  FOUND
   is the character that scanning found (either '-' or ','), and START
   is the start of the line that FOUND points to, hence when reading
   backwards, we must not read any character before START.  Returns a
   pointer to the next non-false-positive delimiter character, or NULL
   if none was found.  */

static const char *
skip_op_false_positives (const char *start, const char *found)
{
  while (found != NULL && is_cp_operator (start, found))
    {
      if (found[0] == '-' && found[1] == '-')
        start = found + 2;
      else
        start = found + 1;
      found = find_toplevel_char (start, *found);
    }

  return found;
}

/* Assuming both FIRST and NEW_TOK point into the same string, return
   the pointer that is closer to the start of the string.  If FIRST is
   NULL, returns NEW_TOK.  If NEW_TOK is NULL, returns FIRST.  */

static const char *
first_of (const char *first, const char *new_tok)
{
  if (first == NULL)
    return new_tok;
  else if (new_tok != NULL && new_tok < first)
    return new_tok;
  else
    return first;
}

/* A lexer for functions in explicit locations.  This function will
   advance INP past a function until the next option, or until end of
   string.  Returns a malloc'd copy of the lexed string or NULL if no
   lexing was done.  */

static gdb::unique_xmalloc_ptr<char>
explicit_location_lex_one_function (const char **inp,
                                    const struct language_defn *language,
                                    explicit_completion_info *completion_info)
{
  const char *start = *inp;

  if (*start == '\0')
    return NULL;

  /* If quoted, skip to the ending quote.  */
  if (strchr (get_gdb_linespec_parser_quote_characters (), *start))
    {
      char quote_char = *start;

      /* If the input is not an Ada operator, skip to the matching
         closing quote and return the string.  */
      if (!(language->la_language == language_ada
            && quote_char == '\"' && is_ada_operator (start)))
        {
          if (completion_info != NULL)
            completion_info->quoted_arg_start = start;

          const char *end = find_toplevel_char (start + 1, quote_char);

          if (end == NULL)
            {
              if (completion_info == NULL)
                error (_("Unmatched quote, %s."), start);

              end = start + strlen (start);
              *inp = end;
              char *saved = savestring (start + 1, *inp - start - 1);
              return gdb::unique_xmalloc_ptr<char> (saved);
            }

          if (completion_info != NULL)
            completion_info->quoted_arg_end = end;
          *inp = end + 1;
          char *saved = savestring (start + 1, *inp - start - 2);
          return gdb::unique_xmalloc_ptr<char> (saved);
        }
    }

  const char *comma = find_toplevel_char (start, ',');

  /* If we have "-function -myfunction", or perhaps better example,
     "-function -[BasicClass doIt]" (objc selector), treat
     "-myfunction" as the function name.  I.e., skip the first char if
     it is an hyphen.  Don't skip the first char always, because we
     may have C++ "operator<", and find_toplevel_char needs to see the
     'o' in that case.  */
  const char *hyphen
    = (*start == '-'
       ? find_toplevel_char (start + 1, '-')
       : find_toplevel_char (start, '-'));

  /* Check for C++ "operator," and "operator-".  */
  comma = skip_op_false_positives (start, comma);
  hyphen = skip_op_false_positives (start, hyphen);

  /* Pick the one that appears first.  */
  const char *end = first_of (hyphen, comma);

  /* See if a linespec keyword appears first.  */
  const char *s = start;
  const char *ws = find_toplevel_char (start, ' ');
  while (ws != NULL && linespec_lexer_lex_keyword (ws + 1) == NULL)
    {
      s = ws + 1;
      ws = find_toplevel_char (s, ' ');
    }
  if (ws != NULL)
    end = first_of (end, ws + 1);

  /* If we don't have any terminator, then take the whole string.  */
  if (end == NULL)
    end = start + strlen (start);

  /* Trim whitespace at the end.  */
  while (end > start && end[-1] == ' ')
    end--;

  *inp = end;

  if (*inp - start > 0)
    return gdb::unique_xmalloc_ptr<char> (savestring (start, *inp - start));

  return NULL;
}

/* See description in location.h.  */

event_location_up
string_to_explicit_location (const char **argp,
                             const struct language_defn *language,
                             explicit_completion_info *completion_info)
{
  event_location_up location;

  /* It is assumed that input beginning with '-' and a non-digit
     character is an explicit location.  "-p" is reserved, though,
     for probe locations.  */
  if (argp == NULL
      || *argp == NULL
      || *argp[0] != '-'
      || !isalpha ((*argp)[1])
      || ((*argp)[0] == '-' && (*argp)[1] == 'p'))
    return NULL;

  location = new_explicit_location (NULL);

  /* Process option/argument pairs.  dprintf_command
     requires that processing stop on ','.  */
  while ((*argp)[0] != '\0' && (*argp)[0] != ',')
    {
      int len;
      const char *start;

      /* Clear these on each iteration, since they should be filled
         with info about the last option.  */
      if (completion_info != NULL)
        {
          completion_info->quoted_arg_start = NULL;
          completion_info->quoted_arg_end = NULL;
        }

      /* If *ARGP starts with a keyword, stop processing
         options.  */
      if (linespec_lexer_lex_keyword (*argp) != NULL)
        break;

      /* Mark the start of the string in case we need to rewind.  */
      start = *argp;

      if (completion_info != NULL)
        completion_info->last_option = start;

      /* Get the option string.  */
      gdb::unique_xmalloc_ptr<char> opt
        = explicit_location_lex_one (argp, language, NULL);

      /* Use the length of the option to allow abbreviations.  */
      len = strlen (opt.get ());

      /* Get the argument string.  */
      *argp = skip_spaces (*argp);

      /* All options have a required argument.  Checking for this
         required argument is deferred until later.  */
      gdb::unique_xmalloc_ptr<char> oarg;
      /* True if we have an argument.  This is required because we'll
         move from OARG before checking whether we have an
         argument.  */
      bool have_oarg = false;

      /* Convenience to consistently set both OARG/HAVE_OARG from
         ARG.  */
      auto set_oarg = [&] (gdb::unique_xmalloc_ptr<char> arg)
        {
          oarg = std::move (arg);
          have_oarg = oarg != NULL;
        };

      if (strncmp (opt.get (), "-source", len) == 0)
        {
          set_oarg (explicit_location_lex_one (argp, language,
                                               completion_info));
          EL_EXPLICIT (location)->source_filename = oarg.release ();
        }
      else if (strncmp (opt.get (), "-function", len) == 0)
        {
          set_oarg (explicit_location_lex_one_function (argp, language,
                                                        completion_info));
          EL_EXPLICIT (location)->function_name = oarg.release ();
        }
      else if (strncmp (opt.get (), "-line", len) == 0)
        {
          set_oarg (explicit_location_lex_one (argp, language, NULL));
          *argp = skip_spaces (*argp);
          if (have_oarg)
            {
              EL_EXPLICIT (location)->line_offset
                = linespec_parse_line_offset (oarg.get ());
              continue;
            }
        }
      else if (strncmp (opt.get (), "-label", len) == 0)
        {
          set_oarg (explicit_location_lex_one (argp, language, completion_info));
          EL_EXPLICIT (location)->label_name = oarg.release ();
        }
      /* Only emit an "invalid argument" error for options
         that look like option strings.  */
      else if (opt.get ()[0] == '-' && !isdigit (opt.get ()[1]))
        {
          if (completion_info == NULL)
            error (_("invalid explicit location argument, \"%s\""), opt.get ());
        }
      else
        {
          /* End of the explicit location specification.
             Stop parsing and return whatever explicit location was
             parsed.  */
          *argp = start;
          return location;
        }

      *argp = skip_spaces (*argp);

      /* It's a little lame to error after the fact, but in this
         case, it provides a much better user experience to issue
         the "invalid argument" error before any missing
         argument error.  */
      if (!have_oarg && completion_info == NULL)
        error (_("missing argument for \"%s\""), opt.get ());
    }

  /* One special error check:  If a source filename was given
     without offset, function, or label, issue an error.  */
  if (EL_EXPLICIT (location)->source_filename != NULL
      && EL_EXPLICIT (location)->function_name == NULL
      && EL_EXPLICIT (location)->label_name == NULL
      && (EL_EXPLICIT (location)->line_offset.sign == LINE_OFFSET_UNKNOWN)
      && completion_info == NULL)
    {
      error (_("Source filename requires function, label, or "
               "line offset."));
    }

  return location;
}

/* See description in location.h.  */

event_location_up
string_to_event_location_basic (const char **stringp,
                                const struct language_defn *language)
{
  event_location_up location;
  const char *cs;

  /* Try the input as a probe spec.  */
  cs = *stringp;
  if (cs != NULL && probe_linespec_to_ops (&cs) != NULL)
    {
      location = new_probe_location (*stringp);
      *stringp += strlen (*stringp);
    }
  else
    {
      /* Try an address location.  */
      if (*stringp != NULL && **stringp == '*')
        {
          const char *arg, *orig;
          CORE_ADDR addr;

          orig = arg = *stringp;
          addr = linespec_expression_to_pc (&arg);
          location = new_address_location (addr, orig, arg - orig);
          *stringp += arg - orig;
        }
      else
        {
          /* Everything else is a linespec.  */
          location = new_linespec_location (stringp);
        }
    }

  return location;
}

/* See description in location.h.  */

event_location_up
string_to_event_location (const char **stringp,
                          const struct language_defn *language)
{
  const char *arg, *orig;

  /* Try an explicit location.  */
  orig = arg = *stringp;
  event_location_up location = string_to_explicit_location (&arg, language, NULL);
  if (location != NULL)
    {
      /* It was a valid explicit location.  Advance STRINGP to
         the end of input.  */
      *stringp += arg - orig;
    }
  else
    {
      /* Everything else is a "basic" linespec, address, or probe
         location.  */
      location = string_to_event_location_basic (stringp, language);
    }

  return location;
}

/* See description in location.h.  */

int
event_location_empty_p (const struct event_location *location)
{
  switch (EL_TYPE (location))
    {
    case LINESPEC_LOCATION:
      /* Linespecs are never "empty."  (NULL is a valid linespec)  */
      return 0;

    case ADDRESS_LOCATION:
      return 0;

    case EXPLICIT_LOCATION:
      return (EL_EXPLICIT (location) == NULL
              || (EL_EXPLICIT (location)->source_filename == NULL
                  && EL_EXPLICIT (location)->function_name == NULL
                  && EL_EXPLICIT (location)->label_name == NULL
                  && (EL_EXPLICIT (location)->line_offset.sign
                      == LINE_OFFSET_UNKNOWN)));

    case PROBE_LOCATION:
      return EL_PROBE (location) == NULL;

    default:
      gdb_assert_not_reached ("unknown event location type");
    }
}

/* See description in location.h.  */

void
set_event_location_string (struct event_location *location,
                           const char *string)
{
  xfree (EL_STRING (location));
  EL_STRING (location) = string == NULL ?  NULL : xstrdup (string);
}