From 832d4ba912214f6bade04ba80d41b16d8cbf10f4 Mon Sep 17 00:00:00 2001
From: Tom Kelly <ctk21@cl.cam.ac.uk>
Date: Thu, 19 Nov 2020 09:20:09 +0000
Subject: [PATCH] Must allocate main stack *after* creation of the stack cache

fix debug memory guard in caml_free_stack
---
 runtime/domain.c | 17 +++++++++--------
 runtime/fiber.c  | 11 +++++++----
 2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/runtime/domain.c b/runtime/domain.c
index e6e3514bb90..eee81f99ca0 100644
--- a/runtime/domain.c
+++ b/runtime/domain.c
@@ -274,21 +274,22 @@ static void create_domain(uintnat initial_minor_heap_wsize) {
       goto reallocate_minor_heap_failure;
     }
 
-    domain_state->current_stack =
-        caml_alloc_main_stack(Stack_size / sizeof(value));
-    if(domain_state->current_stack == NULL) {
-      goto alloc_main_stack_failure;
-    }
-
     domain_state->dls_root = caml_create_root_noexc(Val_unit);
     if(domain_state->dls_root == NULL) {
       goto create_root_failure;
     }
+
     domain_state->stack_cache = caml_alloc_stack_cache();
     if(domain_state->stack_cache == NULL) {
       goto create_stack_cache_failure;
     }
 
+    domain_state->current_stack =
+        caml_alloc_main_stack(Stack_size / sizeof(value));
+    if(domain_state->current_stack == NULL) {
+      goto alloc_main_stack_failure;
+    }
+
     domain_state->backtrace_buffer = NULL;
 #ifndef NATIVE_CODE
     domain_state->external_raise = NULL;
@@ -296,11 +297,11 @@ static void create_domain(uintnat initial_minor_heap_wsize) {
 #endif
     goto domain_init_complete;
 
+  caml_free_stack(domain_state->current_stack);
+alloc_main_stack_failure:
 create_stack_cache_failure:
   caml_delete_root(domain_state->dls_root);
 create_root_failure:
-  caml_free_stack(domain_state->current_stack);
-alloc_main_stack_failure:
 reallocate_minor_heap_failure:
   caml_teardown_major_gc();
 init_major_gc_failure:
diff --git a/runtime/fiber.c b/runtime/fiber.c
index 9550e5b4c41..ecd60c18f72 100644
--- a/runtime/fiber.c
+++ b/runtime/fiber.c
@@ -74,8 +74,8 @@ static struct stack_info* alloc_size_class_stack_noexc(mlsize_t wosize, struct s
 
   if (size_bucket != NULL && *size_bucket != NULL) {
     stack = *size_bucket;
-    CAMLassert(stack->size_bucket == stack_cache_bucket(wosize));
     *size_bucket = (struct stack_info*)stack->exception_ptr;
+    CAMLassert(stack->size_bucket == stack_cache_bucket(wosize));
     hand = stack->handler;
   } else {
     /* couldn't get a cached stack, so have to create one */
@@ -418,13 +418,16 @@ void caml_free_stack (struct stack_info* stack)
 {
   CAMLnoalloc;
   CAMLassert(stack->magic == 42);
-#ifdef DEBUG
-  memset(stack, 0x42, (char*)stack->handler - (char*)stack);
-#endif
   if (stack->size_bucket != NULL) {
     stack->exception_ptr = (void*)(*stack->size_bucket);
     *stack->size_bucket = stack;
+#ifdef DEBUG
+    memset(Stack_base(stack), 0x42, (Stack_high(stack)-Stack_base(stack))*sizeof(value));
+#endif
   } else {
+#ifdef DEBUG
+    memset(stack, 0x42, (char*)stack->handler - (char*)stack);
+#endif
     caml_stat_free(stack);
   }
 }