First commit

Makefile

+
+override CXXFLAGS += -std=c++17 -Isrc
+
+default: calc
+
+calc: src/main.cpp src/calc.cpp
+	$(CXX) $(CXXFLAGS) -o $@ $^ 
+
+unit_test: test/main.o test/test.o src/calc.o
+	$(CXX) $(CXXFLAGS) -o $@ $^ -Isrc
+
+run_test: unit_test
+	./unit_test
+
+fuzz_calc: src/main.cpp src/calc.cpp
+	afl-g++ $(CXXFLAGS) -o $@ $^
+
+fuzz: fuzz_calc
+	rm -rf out
+	afl-fuzz -i in -o out -- ./fuzz_calc
+
+clean:
+	rm -rf calc fuzz_calc unit_test out src/*.o test/*.o

default.nix

+with import (import ./nixpkgs.nix) {};
+stdenv.mkDerivation {
+  name = "rpn-calculator";
+  src = ./.;
+  buildInputs = [ catch2 ];
+
+  doCheck = true;
+  checkTarget = "run_test";
+
+  installPhase = ''
+    mkdir -p $out
+    find . -executable -type f -exec cp {} $out \;
+  '';
+}

fuzz_seconds.sh

+#!/usr/bin/env bash
+
+fuzz_seconds=${1:-10} # 10 seconds by default
+echo "Going to fuzz for $fuzz_seconds seconds."
+
+set -e
+
+afl-fuzz -i in -o out -- ./fuzz_calc &
+afl_pid=$!
+
+sleep $fuzz_seconds
+kill $afl_pid

in/a.txt

+11+3+2/

in/b.txt

+11/

nixpkgs.nix

+builtins.fetchTarball {
+  url = "https://github.com/nixos/nixpkgs/archive/859ce47b023d80ccbcf446a112c813972a5949b6.tar.gz";
+  sha256 = "14rmrpzbxbf8p4v70n39bvxm9qhnwlg4pjkzf7ya6n697g8yd1wx";
+}

release.nix

+with import (import ./nixpkgs.nix) {};
+
+let
+  rpncalc = import ./default.nix;
+  afl_rpncalc = rpncalc.overrideAttrs (_: {
+    nativeBuildInputs = [ afl ];
+    makeFlags = [ "fuzz_calc" ];
+    doCheck = false;
+  });
+in {
+  inherit rpncalc afl_rpncalc;
+  sanitized = rpncalc.overrideAttrs (_: {
+    CXXFLAGS = "-fsanitize=undefined -fsanitize=address";
+  });
+
+  fuzz_rpncalc = afl_rpncalc.overrideAttrs (o: {
+    nativeBuildInputs = o.nativeBuildInputs ++ [ gnuplot which ];
+    preConfigure = ''
+      patchShebangs fuzz_seconds.sh
+    '';
+    postBuild = ''
+      ./fuzz_seconds.sh 10
+      afl-plot out graph
+    '';
+    installPhase = ''
+      cp -r out $out
+      cp -r graph $out/
+
+      mkdir -p $out/nix-support
+      echo report testlog $out graph/index.html > $out/nix-support/hydra-build-products
+    '';
+  });
+}

src/calc.cpp

+#include "calc.hpp"
+
+#include <stack>
+#include <stdexcept>
+
+int plus(    int a, int b) { return a + b; }
+int minus(   int a, int b) { return a - b; }
+int multiply(int a, int b) { return a * b; }
+int divide(  int a, int b) { return a / b; }
+
+int pop_stack(auto &stack) {
+  const auto ret{stack.top()};
+  stack.pop();
+  return ret;
+}
+
+void change_stack_state(auto &operation, auto &stack) {
+  const auto op_b{pop_stack(stack)};
+  const auto op_a{pop_stack(stack)};
+  stack.push(operation(op_a, op_b));
+}
+
+int evaluate(const std::string &s) {
+  std::stack<int> stack;
+
+  for (const char c : s) {
+    switch (c) {
+    case '+': change_stack_state(plus,     stack); break;
+    case '-': change_stack_state(minus,    stack); break;
+    case '*': change_stack_state(multiply, stack); break;
+    case '/': change_stack_state(divide,   stack); break;
+    case '0'...'9': stack.push(c - '0'); break;
+    }
+  }
+
+  return {stack.top()};
+}

src/calc.hpp

+#pragma once
+
+#include <string>
+
+int evaluate(const std::string &s);

src/main.cpp

+#include "calc.hpp"
+
+#include <iostream>
+
+int main() {
+  std::string user_input;
+  std::cin >> user_input;
+
+  if (user_input.empty()) { std::cout << "Empty input\n"; return 1; }
+
+  std::cout << "User input is \"" << user_input << "\"\n";
+
+  const int result{evaluate(user_input)};
+  std::cout << "Result is: " << result << '\n';
+}

test/main.cpp

+#include <calc.hpp>
+
+#define CATCH_CONFIG_MAIN
+#include <catch2/catch.hpp>

test/test.cpp

+#include <calc.hpp>
+
+#include <catch2/catch.hpp>
+
+TEST_CASE( "some example calculations", "[calc]") {
+  REQUIRE( evaluate("11+") == 2 );
+  REQUIRE( evaluate("12+2-3*") == 3 );
+}