1 files changed, 82 insertions, 0 deletions
diff --git a/stdlib/setenv.h b/stdlib/setenv.h
new file mode 100644
index 0000000..7cbf9f2
--- /dev/null
+++ b/stdlib/setenv.h
@@ -0,0 +1,82 @@
+/* Common declarations for the setenv/getenv family of functions.
+   Copyright (C) 2024-2025 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _SETENV_H
+#define _SETENV_H
+
+#include <atomic.h>
+#include <stdbool.h>
+
+/* We use an exponential sizing policy for environment arrays.  The
+   arrays are not deallocating during the lifetime of the process.
+   This adds between one and two additional pointers per active
+   environemnt entry, on top of what is used by setenv to keep track
+   of environment values used before.  */
+struct environ_array
+{
+  /* The actual environment array.  Use a separate allocation (and not
+     a flexible array member) so that calls like free (environ) that
+     have been encountered in some applications do not crash
+     immediately.  With such a call, if the application restores the
+     original environ pointer at process start and does not modify the
+     environment again, a use-after-free situation only occurs during
+     __libc_freeres, which is only called during memory debugging.
+     With subsequent setenv calls, there is still heap corruption, but
+     that happened with the old realloc-based implementation, too.  */
+  char **array;
+  size_t allocated;             /* Number of allocated array elments.  */
+  struct environ_array *next;   /* Previously used environment array.  */
+};
+
+/* After initialization, and until the user resets environ (perhaps by
+   calling clearenv), &__environ[0] == &environ_array_list->array[0].  */
+extern struct environ_array *__environ_array_list attribute_hidden;
+
+/* Returns true if EP (which should be an __environ value) is a
+   pointer managed by setenv.  */
+static inline bool
+__environ_is_from_array_list (char **ep)
+{
+  struct environ_array *eal = atomic_load_relaxed (&__environ_array_list);
+  return eal != NULL && eal->array == ep;
+}
+
+/* Counter for detecting concurrent modification in unsetenv.
+   Ideally, this should be a 64-bit counter that cannot wrap around,
+   but given that counter wrapround is probably impossible to hit
+   (2**32 operations in unsetenv concurrently with getenv), using
+   <atomic_wide_counter.h> seems unnecessary.  */
+#if __HAVE_64B_ATOMICS
+typedef uint64_t environ_counter;
+#else
+typedef uint32_t environ_counter;
+#endif
+
+/* Updated by unsetenv to detect multiple overwrites in getenv.  */
+extern environ_counter __environ_counter attribute_hidden;
+
+/* This function is used by `setenv' and `putenv'.  The difference between
+   the two functions is that for the former must create a new string which
+   is then placed in the environment, while the argument of `putenv'
+   must be used directly.  This is all complicated by the fact that we try
+   to reuse values once generated for a `setenv' call since we can never
+   free the strings.  */
+int __add_to_environ (const char *name, const char *value,
+                      const char *combines, int replace) attribute_hidden;
+
+#endif /* _SETENV_H */