From 278da25c0c285981266f05adbef73a0abd455dd7 Mon Sep 17 00:00:00 2001
From: Atreya Bain <christophervrose@gmail.com>
Date: Thu, 1 Oct 2020 19:42:23 +0530
Subject: [PATCH] Prevent pointer going below zero

---
 src/executeBFE.cpp | 4 ++++
 src/main.cpp       | 6 +++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/executeBFE.cpp b/src/executeBFE.cpp
index 92d5dc6..1fca687 100644
--- a/src/executeBFE.cpp
+++ b/src/executeBFE.cpp
@@ -20,6 +20,9 @@ Any executeBGE::visitNumberedStmt(bfeParser::NumberedStmtContext *ctx){
 }
 
 Any executeBGE::visitPtrIncr(bfeParser::PtrIncrContext *ctx){
+    if(memory.size()<pointer){
+        memory.push_back(0);
+    }
     memory[pointer]++;
     return Any();
 }
@@ -35,6 +38,7 @@ Any executeBGE::visitPtrRight(bfeParser::PtrRightContext *ctx){
 }
 
 Any executeBGE::visitPtrLeft(bfeParser::PtrLeftContext *ctx){
+    if(pointer==0) throw std::string("Decrement below zero");
     pointer--;
     return Any();
 }
diff --git a/src/main.cpp b/src/main.cpp
index afda098..64f1f65 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -30,6 +30,10 @@ int main(int argc, const char *argv[])
     // tree::ParseTreeWalker::DEFAULT.walk(&listener, tree);
 
     executeBGE* visitor = new executeBGE();
-    auto resultAny = visitor->visit(tree);
+    try{
+        visitor->visit(tree);
+    }catch(std::string e){
+        std::cout<<"Illegal:"<<e;
+    }
     return 0;
 }
\ No newline at end of file