add clearenv

Signed-off-by: Mattias Andrée <maandree@member.fsf.org>

1 files changed, 58 insertions, 0 deletions

diff --git a/src/stdlib/clearenv.c b/src/stdlib/clearenv.c
new file mode 100644
index 0000000..e393c01
--- /dev/null
+++ b/src/stdlib/clearenv.c
@@ -0,0 +1,58 @@
+/**
+ * slibc — Yet another C library
+ * Copyright © 2015  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * 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 <stdlib.h>
+
+
+
+/**
+ * The process's environment variables.
+ */
+extern char** environ;
+
+
+
+/**
+ * This function shall in some manner clear the environment.
+ * 
+ * To minimise the risk of fatal race conditions, this
+ * implementation will set the first element in
+ * `extern char** environ` to `NULL`, unless `environ`
+ * itself is `NULL`. This also reduces that risk that
+ * programs stop working when switching to slibc.
+ * 
+ * The exact behaviour of this function depeneds of the
+ * implementations. Depending on the implementation,
+ * this may or may not entail setting `environ` to `NULL`.
+ * 
+ * This function is a very common non-standard extension.
+ * 
+ * @etymology  (Clear) the (env)ironment!
+ * 
+ * @returns  This function is always successful, and will
+ *           always return zero. However, according to the
+ *           specifications, it shall return -1 on failure.
+ * 
+ * @since  Always.
+ */
+int clearenv(void)
+{
+  if (environ != NULL)
+    *environ = NULL;
+  return 0;
+}
+