/* Copyright (C) 1992, 1995-2002, 2005-2020 Free Software Foundation, Inc.

   This file is part of the GNU C 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 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 <https://www.gnu.org/licenses/>.  */

/* Don't use __attribute__ __nonnull__ in this compilation unit.  Otherwise gcc

   optimizes away the name == NULL test below.  */

#define _GL_ARG_NONNULL(params)

#include <config.h>

/* Specification.  */

#include <stdlib.h>

#include <errno.h>

#if !_LIBC

# define __set_errno(ev) ((errno) = (ev))

#endif

#include <string.h>

#include <unistd.h>

#if !_LIBC

# define __environ      environ

#endif

#if _LIBC

/* This lock protects against simultaneous modifications of 'environ'.  */

# include <bits/libc-lock.h>

__libc_lock_define_initialized (static, envlock)

# define LOCK   __libc_lock_lock (envlock)

# define UNLOCK __libc_lock_unlock (envlock)

#else

# define LOCK

# define UNLOCK

#endif

/* In the GNU C library we must keep the namespace clean.  */

#ifdef _LIBC

# define unsetenv __unsetenv

#endif

#if _LIBC || !HAVE_UNSETENV

int

unsetenv (const char *name)

{

  size_t len;

  char **ep;

  if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)

    {

      __set_errno (EINVAL);

      return -1;

    }

  len = strlen (name);

  LOCK;

  ep = __environ;

  while (*ep != NULL)

    if (!strncmp (*ep, name, len) && (*ep)[len] == '=')

      {

        /* Found it.  Remove this pointer by moving later ones back.  */

        char **dp = ep;

        do

          dp[0] = dp[1];

        while (*dp++);

        /* Continue the loop in case NAME appears again.  */

      }

    else

      ++ep;

  UNLOCK;

  return 0;

}

#ifdef _LIBC

# undef unsetenv

weak_alias (__unsetenv, unsetenv)

#endif

#else /* HAVE_UNSETENV */

# undef unsetenv

# if !HAVE_DECL_UNSETENV

#  if VOID_UNSETENV

extern void unsetenv (const char *);

#  else

extern int unsetenv (const char *);

#  endif

# endif

/* Call the underlying unsetenv, in case there is hidden bookkeeping

   that needs updating beyond just modifying environ.  */

int

rpl_unsetenv (const char *name)

{

  int result = 0;

  if (!name || !*name || strchr (name, '='))

    {

      errno = EINVAL;

      return -1;

    }

  while (getenv (name))

# if !VOID_UNSETENV

    result =

# endif

      unsetenv (name);

  return result;

}

#endif /* HAVE_UNSETENV */