343 lines
8.2 KiB
C
343 lines
8.2 KiB
C
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/* Copyright (C) 1992-2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#if HAVE_CONFIG_H
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# include <config.h>
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#endif
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/* Pacify GCC; see the commentary about VALLEN below. This is needed
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at least through GCC 4.9.2. Pacify GCC for the entire file, as
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there seems to be no way to pacify GCC selectively, only for the
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place where it's needed. Do not use DIAG_IGNORE_NEEDS_COMMENT
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here, as it's not defined yet. */
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#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
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#include <errno.h>
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#if !_LIBC
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# if !defined errno && !defined HAVE_ERRNO_DECL
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extern int errno;
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# endif
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# define __set_errno(ev) ((errno) = (ev))
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#endif
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#if _LIBC || HAVE_STDLIB_H
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# include <stdlib.h>
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#endif
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#if _LIBC || HAVE_STRING_H
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# include <string.h>
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#endif
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#if _LIBC || HAVE_UNISTD_H
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# include <unistd.h>
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#endif
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#if !_LIBC
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# define __environ environ
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# ifndef HAVE_ENVIRON_DECL
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extern char **environ;
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# endif
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#endif
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#if _LIBC
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/* This lock protects against simultaneous modifications of `environ'. */
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# include <libc-lock.h>
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__libc_lock_define_initialized (static, envlock)
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# define LOCK __libc_lock_lock (envlock)
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# define UNLOCK __libc_lock_unlock (envlock)
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#else
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# define LOCK
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# define UNLOCK
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#endif
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/* In the GNU C library we must keep the namespace clean. */
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#ifdef _LIBC
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# define setenv __setenv
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# define unsetenv __unsetenv
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# define clearenv __clearenv
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# define tfind __tfind
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# define tsearch __tsearch
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#endif
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/* In the GNU C library implementation we try to be more clever and
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allow arbitrarily many changes of the environment given that the used
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values are from a small set. Outside glibc this will eat up all
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memory after a while. */
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#if defined _LIBC || (defined HAVE_SEARCH_H && defined HAVE_TSEARCH \
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&& defined __GNUC__)
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# define USE_TSEARCH 1
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# include <search.h>
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/* This is a pointer to the root of the search tree with the known
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values. */
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static void *known_values;
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# define KNOWN_VALUE(Str) \
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({ \
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void *value = tfind (Str, &known_values, (__compar_fn_t) strcmp); \
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value != NULL ? *(char **) value : NULL; \
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})
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# define STORE_VALUE(Str) \
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tsearch (Str, &known_values, (__compar_fn_t) strcmp)
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#else
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# undef USE_TSEARCH
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# define KNOWN_VALUE(Str) NULL
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# define STORE_VALUE(Str) do { } while (0)
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#endif
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/* If this variable is not a null pointer we allocated the current
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environment. */
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static char **last_environ;
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/* This function is used by `setenv' and `putenv'. The difference between
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the two functions is that for the former must create a new string which
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is then placed in the environment, while the argument of `putenv'
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must be used directly. This is all complicated by the fact that we try
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to reuse values once generated for a `setenv' call since we can never
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free the strings. */
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int
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__add_to_environ (const char *name, const char *value, const char *combined,
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int replace)
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{
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char **ep;
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size_t size;
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/* Compute lengths before locking, so that the critical section is
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less of a performance bottleneck. VALLEN is needed only if
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COMBINED is null (unfortunately GCC is not smart enough to deduce
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this; see the #pragma at the start of this file). Testing
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COMBINED instead of VALUE causes setenv (..., NULL, ...) to dump
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core now instead of corrupting memory later. */
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const size_t namelen = strlen (name);
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size_t vallen;
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if (combined == NULL)
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vallen = strlen (value) + 1;
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LOCK;
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/* We have to get the pointer now that we have the lock and not earlier
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since another thread might have created a new environment. */
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ep = __environ;
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size = 0;
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if (ep != NULL)
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{
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for (; *ep != NULL; ++ep)
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if (!strncmp (*ep, name, namelen) && (*ep)[namelen] == '=')
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break;
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else
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++size;
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}
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if (ep == NULL || __builtin_expect (*ep == NULL, 1))
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{
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char **new_environ;
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/* We allocated this space; we can extend it. Avoid using the raw
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reallocated pointer to avoid GCC -Wuse-after-free. */
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uintptr_t ip_last_environ = (uintptr_t)last_environ;
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new_environ = (char **) realloc (last_environ,
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(size + 2) * sizeof (char *));
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if (new_environ == NULL)
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{
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UNLOCK;
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return -1;
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}
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if ((uintptr_t)__environ != ip_last_environ)
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memcpy ((char *) new_environ, (char *) __environ,
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size * sizeof (char *));
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new_environ[size] = NULL;
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new_environ[size + 1] = NULL;
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ep = new_environ + size;
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last_environ = __environ = new_environ;
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}
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if (*ep == NULL || replace)
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{
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char *np;
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/* Use the user string if given. */
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if (combined != NULL)
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np = (char *) combined;
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else
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{
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const size_t varlen = namelen + 1 + vallen;
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#ifdef USE_TSEARCH
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char *new_value;
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int use_alloca = __libc_use_alloca (varlen);
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if (__builtin_expect (use_alloca, 1))
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new_value = (char *) alloca (varlen);
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else
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{
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new_value = malloc (varlen);
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if (new_value == NULL)
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{
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UNLOCK;
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return -1;
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}
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}
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# ifdef _LIBC
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__mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
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value, vallen);
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# else
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memcpy (new_value, name, namelen);
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new_value[namelen] = '=';
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memcpy (&new_value[namelen + 1], value, vallen);
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# endif
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np = KNOWN_VALUE (new_value);
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if (__glibc_likely (np == NULL))
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#endif
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{
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#ifdef USE_TSEARCH
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if (__glibc_unlikely (! use_alloca))
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np = new_value;
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else
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#endif
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{
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np = malloc (varlen);
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if (__glibc_unlikely (np == NULL))
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{
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UNLOCK;
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return -1;
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}
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#ifdef USE_TSEARCH
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memcpy (np, new_value, varlen);
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#else
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memcpy (np, name, namelen);
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np[namelen] = '=';
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memcpy (&np[namelen + 1], value, vallen);
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#endif
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}
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/* And remember the value. */
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STORE_VALUE (np);
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}
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#ifdef USE_TSEARCH
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else
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{
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if (__glibc_unlikely (! use_alloca))
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free (new_value);
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}
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#endif
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}
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*ep = np;
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}
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UNLOCK;
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return 0;
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}
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int
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setenv (const char *name, const char *value, int replace)
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{
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if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
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{
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__set_errno (EINVAL);
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return -1;
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}
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return __add_to_environ (name, value, NULL, replace);
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}
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int
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unsetenv (const char *name)
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{
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size_t len;
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char **ep;
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if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
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{
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__set_errno (EINVAL);
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return -1;
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}
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len = strlen (name);
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LOCK;
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ep = __environ;
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if (ep != NULL)
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while (*ep != NULL)
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{
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if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
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{
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/* Found it. Remove this pointer by moving later ones back. */
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char **dp = ep;
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do
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dp[0] = dp[1];
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while (*dp++);
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/* Continue the loop in case NAME appears again. */
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}
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else
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++ep;
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}
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UNLOCK;
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return 0;
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}
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/* The `clearenv' was planned to be added to POSIX.1 but probably
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never made it. Nevertheless the POSIX.9 standard (POSIX bindings
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for Fortran 77) requires this function. */
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int
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clearenv (void)
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{
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LOCK;
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if (__environ == last_environ && __environ != NULL)
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{
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/* We allocated this environment so we can free it. */
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free (__environ);
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last_environ = NULL;
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}
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/* Clear the environment pointer removes the whole environment. */
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__environ = NULL;
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UNLOCK;
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return 0;
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}
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#ifdef _LIBC
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libc_freeres_fn (free_mem)
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{
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/* Remove all traces. */
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clearenv ();
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/* Now remove the search tree. */
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__tdestroy (known_values, free);
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known_values = NULL;
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}
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# undef setenv
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# undef unsetenv
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# undef clearenv
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weak_alias (__setenv, setenv)
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weak_alias (__unsetenv, unsetenv)
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weak_alias (__clearenv, clearenv)
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#endif
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