From dbeab0d63b21c14e9c462c08c8f776e9428b853c Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Sun, 17 Oct 2021 12:51:51 +0200
Subject: Add stack protection for recursive funcs

---
 src/bootstrap/primitives.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

(limited to 'src/bootstrap/primitives.c')

diff --git a/src/bootstrap/primitives.c b/src/bootstrap/primitives.c
index a814e40..0403e3a 100644
--- a/src/bootstrap/primitives.c
+++ b/src/bootstrap/primitives.c
@@ -5,6 +5,7 @@ Object * proc_if(Environment *env, Object *obj);
 Object *
 eval(Environment *env, Object *root) {
     Object* lambda;
+    Object* ret = NULL;
     bool recursion_active = false;
 eval_start:
     switch (root->type) {
@@ -15,7 +16,8 @@ eval_start:
         case OBJ_TYPE_BOOL:
         case OBJ_TYPE_NIL:
         case OBJ_TYPE_STRING: {
-            return root;
+            ret = root;
+            goto eval_success;
         } break;
         case OBJ_TYPE_SYMBOL: {
             Object *val = env_lookup(env, root);
@@ -26,7 +28,8 @@ eval_start:
                 });
                 return obj_err;
             }
-            return val;
+            ret = val;
+            goto eval_success;
         } break;
         case OBJ_TYPE_PAIR: {
             if (root->car->type == OBJ_TYPE_SYMBOL) {
@@ -64,7 +67,8 @@ eval_start:
                         }
                         goto eval_start;
                     }
-                    return val->proc(env, root->cdr);
+                    ret = val->proc(env, root->cdr);
+                    goto eval_success;
                 }
                 if (val->type == OBJ_TYPE_LAMBDA) {
                     lambda = val;
@@ -86,8 +90,12 @@ eval_lambda:
                 args = root->cdr;
                 Object *params = lambda->params;
                 if (!recursion_active) {
-                    env = env_extend(lambda->env, env);
                     recursion_active = true;
+                    // Protect current stack.
+                    Environment *tmp = env_create(lambda->env);
+                    push_active_env(tmp);
+                    // Extend environment.
+                    env = env_extend(tmp, env);
                 }
                 while (params != obj_nil) {
                     if (args == obj_nil) {
@@ -138,6 +146,12 @@ eval_lambda:
         .value = ERR_UNKNOWN_OBJ_TYPE,
     });
     return obj_err;
+eval_success:
+    if (recursion_active) {
+        // Remove stack protector.
+        pop_active_env();
+    }
+    return ret;
 }
 
 Object *
-- 
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