fix side-effect code

Author: mzuenni

test/problems/hellounix/submissions/run_time_error/test-memsize.cc

@@ -13,11 +13,19 @@ using namespace std;
 
 const size_t inc_mb = 128;
 
+template<typename T>
+T use(std::vector<T>& todo) {
+	if (todo.empty()) return {};
+	volatile T* p = &todo[0];
+	// reading a volatile pointer is a side effect and cannot be optimized
+	return p[0];
+}
+
 int main() {
 	vector<vector<char>> vs;
 	while(true) {
 		vs.emplace_back(inc_mb * 1024 * 1024);
-		std::cerr << "Allocated: " << inc_mb * vs.size() << " MB" << std::endl;
+		std::cerr << "Allocated: " << inc_mb * vs.size() << " MB (" << use(vs.back()) << ")" << std::endl;
 	}
 	return 0;
 }

test/problems/hellounix/submissions/run_time_error/test-memsize_512.cc

@@ -16,7 +16,7 @@ const size_t mb = 513;
 template<typename T>
 T use(std::vector<T>& todo) {
 	if (todo.empty()) return {};
-	volatile T* p = &to_use[0];
+	volatile T* p = &todo[0];
 	// reading a volatile pointer is a side effect and cannot be optimized
 	return p[0];
 }