exception section revisited

Author: Oguzhan Katli

inc/advanced_cpp_topics.h

@@ -50,6 +50,7 @@ CREATE_ELEMENT(TemplateTraits);
 
 // Exceptions
 CREATE_ELEMENT(ExceptionUsage);
+CREATE_ELEMENT(ExceptionUnwinding);
 
 // Custom Comparators
 CREATE_ELEMENT(CustomComparatorNeedExample);

main.cpp

@@ -29,6 +29,7 @@ int main(int argc, char *argv[]) {
  .Add<StaticUsageExample>()
  // Exceptions
  .Add<ExceptionUsage>()
+ .Add<ExceptionUnwinding>()
  // CPU Architecture
  .Add<CpuCacheExample>()
  .Add<CountIfRandom>()

src/6-Exceptions/exception_usage.cpp

@@ -101,40 +101,27 @@ namespace exceptions {
  } // namespace custom
 
  namespace rethrow {
- std::exception_ptr eptr; // object to hold exceptions (or nullptr)
- void foo()
+ std::exception_ptr eptr;
+ void thread_func() try
  {
- try {
- throw new std::runtime_error("asdasd");
- }
- catch (...) {
- eptr = std::current_exception(); // save exception for later processing
- }
+ std::this_thread::sleep_for(std::chrono::seconds(1));
+ throw std::runtime_error("abort thread");
  }
-
- void bar()
- {
- if (eptr != nullptr) {
- std::rethrow_exception(eptr); // process saved exception
- }
+ catch (...) {
+ eptr = std::current_exception(); // save exception for later processing
  }
 
- void usage() {
-  foo();
- try
- {
- // lately... 
- bar();
- }
- catch (const std::exception& ex)
- {
+ void usage() 
+ {
+ std::thread(thread_func).join();
+ try {
+ if (eptr != nullptr) {
+  // process saved exception
+  std::rethrow_exception(eptr);
+  }
+ } catch (const std::exception& ex) {
  std::cout << ex.what() << std::endl;
- }
- catch (std::exception* ex)
- {
- std::cout << ex->what() << std::endl;
- }
- catch (...) {
+ } catch (...) {
  std::cout << "catched unknown exception!" << std::endl;
  }
  }
@@ -144,45 +131,43 @@ namespace exceptions {
  {
  struct unwinder
  {
- virtual int unwind() const = 0;
+ virtual ~unwinder() = default;
+ virtual void unwind() const = 0;
  };
 
  void will_throw(int should_throw)
  {
- // x degerinin delete edildigini gostermek icin custom deleter kullaniliyor
- std::unique_ptr<int, std::function<void(int*)>> x(new int(7), [&](int *p) {
- delete p;
- });
- struct unwinder_impl : public unwinder
+ int* val = new int(10);
+ struct stack_cleaner final
+ : public unwinder 
  {
- int* val;
- unwinder_impl(int* _val) : val(_val) {
- ++(*val);
- printf("%s\n", __FUNCTION__);
- }
- ~unwinder_impl() { printf("%s\n", __FUNCTION__); }
+ int*& val;
+ stack_cleaner(int*& _val) 
+ : val(_val) { printf("%s\n", __FUNCTION__); }
+ ~stack_cleaner() { printf("%s\n", __FUNCTION__); }
 
- int unwind() const override
- {
- // val = ?
- return ++(*val);
+ void unwind() const override {
+ if (val) delete val;
  }
  };
- // release build optimizasyonunu ekarte etmek icin
  if (should_throw % 2 == 0)
- throw unwinder_impl(x.get());
+ throw stack_cleaner(val);
+ else
+ delete val;
  }
 
  void usage()
  {
  try
  {
- will_throw(rand());
+ while (true)
+ {
+ will_throw(rand());
+ }
  }
- catch (const unwinder& _unwinder)
+ catch (const unwinder& unwinder)
  {
- int res = _unwinder.unwind();
- std::cout << "result: " << res << "\n";
+ unwinder.unwind();
  }
  }
 
@@ -196,3 +181,8 @@ ELEMENT_CODE(ExceptionUsage) {
  rethrow::usage();
  unwinding::usage();
 }
+
+ELEMENT_CODE(ExceptionUnwinding) {
+ using namespace exceptions;
+ unwinding::usage();
+}