.

Makefile

@@ -30,7 +30,7 @@ endif
 
 # debug and release flags
 
-DEBUG_CFLAGS=-Og -ggdb3 ${WARNINGS} -fno-omit-frame-pointer -fsanitize=address -fsanitize=undefined \
+DEBUG_CFLAGS=-O0 -Og -ggdb3 ${WARNINGS} -fno-omit-frame-pointer -fsanitize=address -fsanitize=undefined \
   -fno-sanitize-recover=all -fstack-protector-strong -fstack-clash-protection -fno-common ${ADD_DBG_FLAGS} \
   -DCHECK_TYCHE_BUGS=1
 DEBUG_LDFLAGS=-fsanitize=address -fsanitize=undefined

lib/stack.c

@@ -77,7 +77,7 @@ static size_t stack_len(Stack* s)
 static TYC_RESULT stack_at(Stack* s, int32_t key, VALUE* v)
 {
     if (key >= 0) {
-        if (key >= s->stack_n)
+        if (stack_top_fp(s) + key >= s->stack_n)
             return T_ERR_STACK_ACCESS_OUT_OF_RANGE;
         *v = s->stack[stack_top_fp(s) + key];
     } else {
@@ -91,7 +91,17 @@ static TYC_RESULT stack_at(Stack* s, int32_t key, VALUE* v)
 
 static TYC_RESULT stack_set(Stack* s, int32_t key, VALUE v)
 {
-    abort(); // TODO
+    if (key >= 0) {
+        if (stack_top_fp(s) + key >= s->stack_n)
+            return T_ERR_STACK_ACCESS_OUT_OF_RANGE;
+        s->stack[stack_top_fp(s) + key] = v;
+    } else {
+        if ((int) stack_top_fp(s) + (int) s->stack_n + key < 0)
+            return T_ERR_STACK_ACCESS_OUT_OF_RANGE;
+        s->stack[s->stack_n + key] = v;
+    }
+
+    return T_OK;
 }
 
 static TYC_RESULT stack_push_fp(Stack* s)