How to debug the handlers?

[zhangzq]

My app showed me an error message:

ERROR: [connection:5] error while handling request: basic_string::_M_replace_aux

I didn't know where the error cames from (even I compiled in debug mode and run in gdb). What should I do?

[eao197]

Hi!

Looks like you get a std::length_error somewhere in your request-handler. That exception is caught by RESTinio and logger.

It's hard to help you because I don't know anything about your code. You can try to place the code in your request-handler into try-catch block:

auto my_request_handler(const restinio::request_handle_t & req) {
  try {
    ... // Your code here.
  }
  catch(const std::exception & x) {
    std::cerr << "Oops! " << x.what() << std::endl; // (1)
  }
}

Then set a breakpoint at (1).

[zhangzq]

Is there an MACRO -- not to catch the exception and let the app core dump, then let me check the error stack (in gdb)?

[eao197]

No, there is no such a macro.

You can comment try/catch blocks here:

restinio/dev/restinio/impl/connection.hpp

Lines 741 to 749 in 0052518

	catch( const std::exception & ex )
	{
	trigger_error_and_close( [&]{
	return fmt::format(
	"[connection:{}] error while handling request: {}",
	this->connection_id(),
	ex.what() );
	} );
	}

[zhangzq]

Hi!

Looks like you get a std::length_error somewhere in your request-handler. That exception is caught by RESTinio and logger.

It's hard to help you because I don't know anything about your code. You can try to place the code in your request-handler into try-catch block:

auto my_request_handler(const restinio::request_handle_t & req) {
  try {
    ... // Your code here.
  }
  catch(const std::exception & x) {
    std::cerr << "Oops! " << x.what() << std::endl; // (1)
  }
}

Then set a breakpoint at (1).

Breakpoint at (1) won't provide the error stack.

[zhangzq]

No, there is no such a macro.

You can comment try/catch blocks here:

restinio/dev/restinio/impl/connection.hpp

Lines 741 to 749 in 0052518

	catch( const std::exception & ex )
	{
	trigger_error_and_close( [&]{
	return fmt::format(
	"[connection:{}] error while handling request: {}",
	this->connection_id(),
	ex.what() );
	} );
	}

Thanks. I comment/uncomment using #ifdef DBUG, but get catched by some other place and show error messsage:

unexpected exception during the handling of incoming data: basic_string::_M_replace_aux

[eao197]

Breakpoint at (1) won't provide the error stack.

Oops. Ok. Let's try something like that:

class dummy_breakpoint {
  bool commited_{false};
public:
  dummy_breakpoint() = default;
  ~dummy_breakpoint() { if(!commited_) std::abort(); } // or just throw std::runtime_error("my exception");

  void commit() { commited_ = true; }
};

// Then in your request-handler:
auto my_request_handler(const restinio::request_handle_t & req) {
  dummy_breakpoint breakpoint;
  ...
  const auto res = req->create_response(...)...;
  dummy_breakpoint.commit();
  return res;
}