From c61108408695d4972bc8b66f65061d9517e333bf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=89milie=20Feral?= <emilie.feral@numworks.com>
Date: Fri, 14 Jun 2019 12:01:00 -0400
Subject: [PATCH] [python] Clean gc_collect and comment to explain potential
 address sanitize error

---
 python/port/port.cpp | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/python/port/port.cpp b/python/port/port.cpp
index 6f01f26ca..ba1106936 100644
--- a/python/port/port.cpp
+++ b/python/port/port.cpp
@@ -138,9 +138,9 @@ void gc_collect(void) {
   /* On the device, the stack is stored in reverse order, but it might not be
    * the case on a computer. We thus have to take the absolute value of the
    * addresses difference. */
-  size_t stackLength;
+  size_t stackLengthInByte;
   void ** scanStart;
-  if ((uintptr_t)python_stack_top > (uintptr_t)&regs) {
+  if ((uintptr_t)python_stack_top > (uintptr_t)regs_ptr) {
 
     /* To compute the stack length:
      *                                  regs
@@ -149,7 +149,7 @@ void gc_collect(void) {
      *                             ^&regs                        ^python_stack_top
      * */
 
-    stackLength = ceil((float)((uintptr_t)python_stack_top - (uintptr_t)&regs) / (float)sizeof(uintptr_t));
+    stackLengthInByte = (uintptr_t)python_stack_top - (uintptr_t)regs_ptr;
     scanStart = regs_ptr;
 
   } else {
@@ -161,12 +161,13 @@ void gc_collect(void) {
      *           ^python_stack_top                ^&regs
      * */
 
-    size_t sizeOfRegs = ceil(((float)sizeof(regs))/(float)sizeof(uintptr_t));
-    stackLength = (size_t)ceil(((float)((uintptr_t)(&regs) - (uintptr_t)python_stack_top)) / (float)sizeof(uintptr_t)) + sizeOfRegs;
+    stackLengthInByte = (uintptr_t)regs_ptr - (uintptr_t)python_stack_top + sizeof(regs);
     scanStart = (void **)python_stack_top;
 
   }
-  gc_collect_root(scanStart, stackLength);
+  /* Memory error detectors might find an error here as they might split regs
+   * and stack memory zones. */
+  gc_collect_root(scanStart, stackLengthInByte/sizeof(void *));
 
   gc_collect_end();
 }