The following dynamic module takes unbounded memory:
/* gcc -I . -g -ggdb -fPIC foo.c -shared -o foo.so && echo running && emacs -Q -L . -batch -l foo */
#include <emacs-module.h>
int plugin_is_GPL_compatible;
int emacs_module_init(struct emacs_runtime *ert) {
emacs_env *env = ert->get_environment(ert);
while (1) {
int i;
for (i = 0; i < 10000; i++) {
emacs_value v = env->make_string(env, "asdads", 3);
env->free_global_ref(env, env->make_global_ref(env, v));
}
env->funcall(env, env->intern(env, "garbage-collect"), 0, NULL);
}
}
This is because env->make_global_ref/env->free_global_ref leak memory.
env->free_global_ref fails to remove values from the hash table of
refcounts. The following patch makes the program above run in constant
space.
--- src/emacs-module.c 2017-06-30 16:00:36.776301646 -0400
+++ src/emacs-module.c 2017-06-30 16:05:01.660120043 -0400
@@ -308,7 +308,7 @@
set_hash_value_slot (h, i, value);
}
else
- hash_remove_from_table (h, value);
+ hash_remove_from_table (h, obj);
}
}