From 2f4fd2388478b369236646aff9cf0411b1360730 Mon Sep 17 00:00:00 2001
From: Calvin Rose <calsrose@gmail.com>
Date: Mon, 12 Feb 2018 17:36:29 -0500
Subject: [PATCH] Add per fiber stack limit.

---
 src/core/fiber.c            | 1 +
 src/core/vm.c               | 5 ++---
 src/include/dst/dstconfig.h | 2 +-
 src/include/dst/dsttypes.h  | 1 +
 4 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/core/fiber.c b/src/core/fiber.c
index afaafe78..096fbe6f 100644
--- a/src/core/fiber.c
+++ b/src/core/fiber.c
@@ -37,6 +37,7 @@ DstFiber *dst_fiber(int32_t capacity) {
         fiber->data = NULL;
     }
     fiber->parent = NULL;
+    fiber->maxstack = DST_STACK_MAX;
     return dst_fiber_reset(fiber);
 }
 
diff --git a/src/core/vm.c b/src/core/vm.c
index 22eeb140..9e182125 100644
--- a/src/core/vm.c
+++ b/src/core/vm.c
@@ -572,11 +572,10 @@ static void *op_lookup[255] = {
     VM_OP(DOP_CALL)
     {
         Dst callee = stack[oparg(2, 0xFFFF)];
-#ifdef DST_STACK_MAX
-        if (dst_vm_fiber->stacktop > DST_STACK_MAX) {
+        if (dst_vm_fiber->maxstack &&
+                dst_vm_fiber->stacktop > dst_vm_fiber->maxstack) {
             vm_throw("stack overflow");
         }
-#endif
         if (dst_checktype(callee, DST_FUNCTION)) {
             func = dst_unwrap_function(callee);
             dst_stack_frame(stack)->pc = pc;
diff --git a/src/include/dst/dstconfig.h b/src/include/dst/dstconfig.h
index 759d4838..167f3356 100644
--- a/src/include/dst/dstconfig.h
+++ b/src/include/dst/dstconfig.h
@@ -123,7 +123,7 @@ extern "C" {
 /* Define max stack size for stacks before raising a stack overflow error.
  * If this is not defined, fiber stacks can grow without limit (until memory
  * runs out) */
-#define DST_STACK_MAX 4096
+#define DST_STACK_MAX 8192
 
 /* Use nanboxed values - uses 8 bytes per value instead of 12 or 16. */
 #define DST_NANBOX
diff --git a/src/include/dst/dsttypes.h b/src/include/dst/dsttypes.h
index f2308716..2b668039 100644
--- a/src/include/dst/dsttypes.h
+++ b/src/include/dst/dsttypes.h
@@ -314,6 +314,7 @@ struct DstFiber {
     int32_t stackstart; /* Beginning of next args */
     int32_t stacktop; /* Top of stack. Where values are pushed and popped from. */
     int32_t capacity;
+    int32_t maxstack; /* Arbitrary defined limit for stack overflow */
     enum {
         DST_FIBER_PENDING,
         DST_FIBER_NEW,