From a9a3cf607ae7a8a3cfaaf44f599f743a0efab0f8 Mon Sep 17 00:00:00 2001
From: Jude Nelson <judecn@gmail.com>
Date: Fri, 5 Mar 2021 17:35:41 -0500
Subject: [PATCH 1/2] fix underflow crash

---
 src/lib.rs | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/lib.rs b/src/lib.rs
index 3c1d889..a75a361 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -89,7 +89,17 @@ pub fn grow<R, F: FnOnce() -> R>(stack_size: usize, callback: F) -> R {
 /// to determine whether a stack switch should be made or not.
 pub fn remaining_stack() -> Option<usize> {
     let current_ptr = current_stack_ptr();
-    get_stack_limit().map(|limit| current_ptr - limit)
+    match get_stack_limit() {
+        Some(limit) => {
+            if current_ptr < limit {
+                None
+            }
+            else {
+                current_ptr - limit
+            }
+        },
+        None => None
+    }
 }
 
 psm_stack_information! (

From 8e4509c1b913dab23e3220d4e58af3377fe9fd92 Mon Sep 17 00:00:00 2001
From: Jude Nelson <judecn@gmail.com>
Date: Fri, 5 Mar 2021 17:56:18 -0500
Subject: [PATCH 2/2] oops; typo

---
 src/lib.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/lib.rs b/src/lib.rs
index a75a361..bdaf835 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -95,7 +95,7 @@ pub fn remaining_stack() -> Option<usize> {
                 None
             }
             else {
-                current_ptr - limit
+                Some(current_ptr - limit)
             }
         },
         None => None