+#if HAVE_SETENV || HAVE_UNSETENV
+
+/* Get setenv(), unsetenv() declarations. */
+#include <stdlib.h>
+
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#if !HAVE_SETENV
+
+/* Set NAME to VALUE in the environment.
+ If REPLACE is nonzero, overwrite an existing value. */
+extern int setenv (const char *name, const char *value, int replace);
+
+#endif
+
+#if !HAVE_UNSETENV
+
+/* Remove the variable NAME from the environment. */
+extern int unsetenv (const char *name);
+
+#endif
+
+#ifdef __cplusplus
+}
+#endif