From 740a968a1200ee93e7bc778d4bd8ec765033f6fe Mon Sep 17 00:00:00 2001
From: Laria Carolin Chabowski <laria@laria.me>
Date: Fri, 23 Jan 2026 21:02:20 +0100
Subject: [PATCH] Fix some GC mistakes

Objects could be cleaned up too early
---
 src/bytecode.c | 42 +++++++++++++++++++++++-------------------
 src/context.c  | 10 ++++++----
 src/eval.c     |  3 +++
 3 files changed, 32 insertions(+), 23 deletions(-)

diff --git a/src/bytecode.c b/src/bytecode.c
index e5fd7c0..f870283 100644
--- a/src/bytecode.c
+++ b/src/bytecode.c
@@ -194,10 +194,10 @@ apfl_instructions_deinit(struct apfl_allocator allocator, struct instruction_lis
 
 #define GET_ARGUMENT(ilist, i, arg)     \
     do {                                \
-        if (i >= ilist->len) {          \
+        if (++i >= ilist->len) {          \
             return;                     \
         }                               \
-        arg = ilist->instructions[++i]; \
+        arg = ilist->instructions[i]; \
     } while (0)
 
 void
@@ -691,22 +691,25 @@ unserialize_string(
             .cap = len,
         };
 
+        if (!apfl_resizable_ensure_cap_for_more_elements(
+            unserializer->gc->allocator,
+            sizeof(struct apfl_string *),
+            (void **)&unserializer->strings,
+            unserializer->strings_len,
+            &unserializer->strings_cap,
+            1
+        )) {
+            FREE_BYTES(unserializer->gc->allocator, buf, len);
+            return false;
+        }
+
         if ((*s = apfl_string_move_into_new_gc_string(unserializer->gc, &tmpstring)) == NULL) {
             FREE_BYTES(unserializer->gc->allocator, buf, len);
             return false;
         }
 
-        if (!apfl_resizable_append(
-            unserializer->gc->allocator,
-            sizeof(struct apfl_string *),
-            (void **)&unserializer->strings,
-            &unserializer->strings_len,
-            &unserializer->strings_cap,
-            &(*s),
-            1
-        )) {
-            return false;
-        }
+        unserializer->strings[unserializer->strings_len] = *s;
+        unserializer->strings_len++;
 
         return true;
     }
@@ -800,6 +803,7 @@ unserialize_milist(
         case MINSN_ARGS_NAME: {
             struct apfl_string *name;
             FMT_TRY(unserialize_string(unserializer, &name));
+            assert(name != NULL);
             FMT_TRY(APPEND_MATCHER_INS_OR_ARG(milist, string, name));
             break;
         }
@@ -879,8 +883,10 @@ set_ilist_nested(
 ) {
     (void)unserializer;
 
-    struct instruction_list **dst = opaque;
-    *dst = ilist;
+    struct instruction_list *dst_ilist = opaque;
+
+    APPEND_INS_OR_ARG(dst_ilist, body, ilist);
+
     return true;
 }
 
@@ -893,7 +899,7 @@ unserialize_ilist(
     size_t line;
     FMT_TRY(unserialize_size(unserializer->r, &line));
 
-    struct apfl_string *filename;
+    struct apfl_string *filename = NULL;
     FMT_TRY(unserialize_string(unserializer, &filename));
 
     size_t tmproots = apfl_gc_tmproots_begin(unserializer->gc);
@@ -968,9 +974,7 @@ unserialize_ilist(
             if (ilist->len >= ilist->cap) {
                 return false;
             }
-            struct instruction_list **dst = &ilist->instructions[ilist->len].body;
-            ilist->len++;
-            FMT_TRY(unserialize_ilist(unserializer, set_ilist_nested, dst));
+            FMT_TRY(unserialize_ilist(unserializer, set_ilist_nested, ilist));
             break;
         }
         case INSN_ARGS_MATCHER: {
diff --git a/src/context.c b/src/context.c
index 8cd0bd8..e0f6354 100644
--- a/src/context.c
+++ b/src/context.c
@@ -703,10 +703,12 @@ visit_matcher_cse(struct matcher_call_stack_entry cse, gc_visitor visitor, void*
     visit_scopes(cse.scopes, visitor, opaque);
     for (size_t i = 0; i < cse.capture_count; i++) {
         apfl_value_visit_gc_object(cse.captures[i], visitor, opaque);
-        visitor(
-            opaque,
-            GC_OBJECT_FROM(cse.transfers[i].var, GC_TYPE_STRING)
-        );
+        if (cse.transfers[i].var != NULL) {
+            visitor(
+                opaque,
+                GC_OBJECT_FROM(cse.transfers[i].var, GC_TYPE_STRING)
+            );
+        }
     }
 }
 
diff --git a/src/eval.c b/src/eval.c
index 93e39bf..ab12356 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -16,6 +16,7 @@ static void evaluate(apfl_ctx ctx, struct func_call_stack_entry *cse);
 static void evaluate_matcher(apfl_ctx ctx, struct matcher_call_stack_entry *cse);
 static void dispatch(apfl_ctx ctx, struct call_stack_entry *cse);
 static void matcher_init_matching(apfl_ctx ctx, struct matcher *matcher, struct scopes scopes);
+static void must_tmproot_add_value(apfl_ctx ctx, struct apfl_value value);
 
 static void
 stack_must_drop(apfl_ctx ctx, apfl_stackidx index)
@@ -361,6 +362,8 @@ return_from_function_inner(apfl_ctx ctx)
         value = (struct apfl_value) { .type = VALUE_NIL };
     }
 
+    must_tmproot_add_value(ctx, value);
+
     call_stack_drop(ctx);
 
     apfl_stack_must_push(ctx, value);