+#ifdef HAVE_PUTENV
+void unputenv(char *p) {
+ char *e = strchr(p, '=');
+ if(!e)
+ return;
+ int len = e - p;
+#ifndef HAVE_UNSETENV
+#ifdef HAVE_MINGW
+ // Windows requires putenv("FOO=") to unset %FOO%
+ len++;
+#endif
+#endif
+ char var[len];
+ strncpy(var, p, len);
+#ifdef HAVE_UNSETENV
+ unsetenv(var);
+#else
+ // We must keep what we putenv() around in memory.
+ // To do this without memory leaks, keep things in a list and reuse if possible.
+ static list_t list = {};
+ for(list_node_t *node = list->head; node; node++) {
+ char *data = node->data;
+ if(!strcmp(data, var)) {
+ putenv(data);
+ return;
+ }
+ }
+ char *data = strcmp(var);
+ list_insert_tail(list, data);
+ putenv(data);
+#endif
+}
+#else
+void putenv(const char *p) {}
+void unputenv(const char *p) {}
+#endif
+