gdbsupport/gdb_tilde_expand.cc

/* Perform tilde expansion on paths for GDB and gdbserver.

   Copyright (C) 2017-2024 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 <algorithm>
#include "filenames.h"
#include "gdb_tilde_expand.h"
#include <glob.h>

/* RAII-style class wrapping "glob".  */

class gdb_glob
{
public:
  /* Construct a "gdb_glob" object by calling "glob" with the provided
     parameters.  This function can throw if "glob" fails.  */
  gdb_glob (const char *pattern, int flags,
	    int (*errfunc) (const char *epath, int eerrno))
  {
    int ret = glob (pattern, flags, errfunc, &m_glob);

    if (ret != 0)
      {
	if (ret == GLOB_NOMATCH)
	  error (_("Could not find a match for '%s'."), pattern);
	else
	  error (_("glob could not process pattern '%s'."),
		 pattern);
      }
  }

  /* Destroy the object and free M_GLOB.  */
  ~gdb_glob ()
  {
    globfree (&m_glob);
  }

  /* Return the GL_PATHC component of M_GLOB.  */
  int pathc () const
  {
    return m_glob.gl_pathc;
  }

  /* Return the GL_PATHV component of M_GLOB.  */
  char **pathv () const
  {
    return m_glob.gl_pathv;
  }

private:
  /* The actual glob object we're dealing with.  */
  glob_t m_glob;
};

/* See gdbsupport/gdb_tilde_expand.h.  */

std::string
gdb_tilde_expand (const char *dir)
{
  if (dir[0] != '~')
    return std::string (dir);

  /* This function uses glob in order to expand the ~.  However, this function
     will fail to expand if the actual dir we are looking for does not exist.
     Given "~/does/not/exist", glob will fail.

     In order to avoid such limitation, we only use glob to expand "~" and keep
     "/does/not/exist" unchanged.

     Similarly, to expand ~gdb/might/not/exist, we only expand "~gdb" using
     glob and leave "/might/not/exist" unchanged.  */
  const std::string d (dir);

  /* Look for the first dir separator (if any) and split d around it.  */
  const auto first_sep
    = std::find_if (d.cbegin (), d.cend(),
		    [] (const char c) -> bool
		      { return IS_DIR_SEPARATOR (c); });
  const std::string to_expand (d.cbegin (), first_sep);
  const std::string remainder (first_sep, d.cend ());

  const gdb_glob glob (to_expand.c_str (), GLOB_TILDE_CHECK, nullptr);

  gdb_assert (glob.pathc () == 1);
  return std::string (glob.pathv ()[0]) + remainder;
}