5983 - fix an emulator bounds-check bug

It was possible for an instruction to write out of bounds of the memory
data structure. Most of the time this worked fine. However if the block
ever got resized and moved the out-of-bounds bytes no longer went along.

1 files changed, 1 insertions, 1 deletions

diff --git a/010---vm.cc b/010---vm.cc
index a0724760..472990a0 100644
--- a/010---vm.cc
+++ b/010---vm.cc
@@ -108,7 +108,7 @@ struct vma {
   uint8_t& data(uint32_t a) {
     assert(match(a));
     uint32_t result_index = a-start;
-    if (_data.size() <= result_index) {
+    if (_data.size() <= result_index+/*largest word size that can be accessed in one instruction*/sizeof(int)) {
       const int align = 0x1000;
       uint32_t result_size = result_index + 1;  // size needed for result_index to be valid
       uint32_t new_size = align_upwards(result_size, align);