CODEWITHSUNDEEP
c#c++dll
Hossein
Hossein

Reputation: 26004

How should I deal with errors in my C++ based dll?

I have created a C++ DLL and I am using it in a C# application. How should I report errors?

Use exceptions and throw my errors, or print them on std::cout or std::cerr, or something else? If I issue an exception inside my DLL, will my C# application be able to catch it? What is the best course of action on this regard?

Upvotes: 4

Views: 1157

Answers (3)

Lochemage
Lochemage

Reputation: 3974

It really depends on how strong the error is. Most libraries that I've seen will return a success or failure result value from their function calls that you can check for manually in your code when you use it. They usually provide another method that just retrieves the error message in case you want to see it.

Save throw exceptions for the really big stuff that you can't continue without, this will force people using your library to fix those errors (or at the very least, see that there is a big problem).

I would not recommend printing anything in the console window, it is a very slow operation and having it in there forces anyone using your library to have that overhead with little option for optimization. If they want to print the error messages, they can just retrieve the error data from your library and print them out themselves.

Upvotes: 1

user645280
user645280

Reputation:

Here's an example output from C# using PInvoke to call a method which throws std::exception.

ex = System.Runtime.InteropServices.SEHException (0x80004005): 
 External component has thrown an exception.
   at ConsoleTester.Program.throw_exception()
   at ConsoleTester.Program.Main(String[] args) in ConsoleTester.cs:line 18

Note: In this case throw_exception() is the exposed native method and it called a sub-method, but you can't see that part of the stack trace. All you get for deepest stack frame is the native boundary.

So, it isn't perfect, but it does work. Returning error codes is probably the most standard way to handle this, but if you're the only consumer of the library it probably won't make much difference.

Note: stdin/stdout is generally the worst way to handle errors. The exception being that it's not so bad to write a custom error handling object or set of routines that everything in the application can access when something goes wrong. (The output from such an interface might sometimes be stdin/stdout or a file or whatever is useful as configured) think log4j or log4net here...

Generally, logging is only part of error handling. You've still got to signal other parts of your application to respond to adverse conditions and (hopefully) recover from them. Here, only error codes or exceptions really work well (and exceptions are to be minimized from main program flow anyways).

Upvotes: 2

japreiss
japreiss

Reputation: 11251

Don't print errors on stdout or stderr! You need to return errors programatically so the C# application has a chance to handle them. What if the host application is a GUI app?

Throwing exceptions from a C++ DLL is fraught with peril. Even if your application was C++, it would have to be compiled with the exact same compiler as the DLL, like @ebyrob said. Calling from C#, I'm not sure.

Best course of action is returning error codes.

Upvotes: 1

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