3 files changed, 11 insertions, 2 deletions
diff --git a/src/parser.c b/src/parser.c
index cdf7c5b..03b835e 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -521,7 +521,7 @@ static void parser_parse_else_if_statement_loop(Parser *self, IfStatement *if_st
         if(!next_else_if)
             break;
         else_if_stmt->next_else_if_stmt = next_else_if;
-        /* else statement, which because they have no conditions; can't be followed by another else statement */
+        /* else statement that has no condition can't be followed by another else statement */
         if(!else_if_stmt->condition)
             break;
         else_if_stmt = next_else_if;
diff --git a/src/program.c b/src/program.c
index 9ec1b41..17aee03 100644
--- a/src/program.c
+++ b/src/program.c
@@ -91,6 +91,10 @@ int amal_program_add_extern_func(amal_program *self, BufferView name, void *func
     ProgramExternFunc extern_func;
     extern_func.func = func_ptr;
     extern_func.args_byte_size = args_byte_size;
+
+    if(hash_map_contains(&self->extern_funcs_map, name))
+        return AMAL_PROGRAM_EXTERN_FUNC_ALREADY_EXISTS;
+
     return hash_map_insert(&self->extern_funcs_map, name, &extern_func);
 }
 
diff --git a/src/std/hash_map.c b/src/std/hash_map.c
index 2b29f2e..48e9e38 100644
--- a/src/std/hash_map.c
+++ b/src/std/hash_map.c
@@ -192,7 +192,8 @@ bool hash_map_get(HashMap *self, BufferView key, void *value) {
         BufferView bucket_key;
         bucket_key = bucket_node_get_key(bucket_node);
         if(hash == bucket_node_get_hash(bucket_node) && self->compare_func(&key, &bucket_key) == 0) {
-            am_memcpy(value, bucket_node_get_value(bucket_node), self->value_type_size);
+            if(value)
+                am_memcpy(value, bucket_node_get_value(bucket_node), self->value_type_size);
             return bool_true;
         }
     }
@@ -200,6 +201,10 @@ bool hash_map_get(HashMap *self, BufferView key, void *value) {
     return bool_false;
 }
 
+bool hash_map_contains(HashMap *self, BufferView key) {
+    return hash_map_get(self, key, NULL);
+}
+
 #define MIN(a, b) ((a) < (b) ? (a) : (b))
 
 int hash_map_compare_string(const void *a, const void *b) {