0x80004005 the answer to almost everything

There's something very frustrating when developing with the Inventor API: when there's a problem, 90% of the time, the answer is 0x80004005.

And that makes debugging very frustrating. With no indication of the nature of the problem, you have to check everything and that can take time, a lot of time.

The documentation doesn't help. Some documentation, like Microsoft's (MSDN), has an Exceptions section for each function/method that lists the exceptions that can be thrown. But in the case of Autodesk Inventor, there's no such information.

As a result, you can spend hours only to realize at the end that the problem comes from a non-existent directory, a property name that doesn't have the right case, or a parameter that isn't within the expected values.

So why don't Autodesk developers return more explicit messages?

It's actually related to the underlying technology: COM. It's a very old technology that dates back to the 90s. At the time, we didn't have standardized exceptions in C++ and we didn't really care about the quality of error messages. When we had an error, we most often wrote:

if (something_bad) return E_FAIL;

And we moved on to something else.

It must be said that to return a more explicit message, you had to use something like:

CComPtr<ICreateErrorInfo> cei;
CreateErrorInfo(&cei);
cei->SetDescription(L"The file is corrupted");
cei->SetSource(L"MonComObject");
CComPtr<IErrorInfo> ei;
cei->QueryInterface(&ei);
SetErrorInfo(0, ei);
return MY_E_BAD_DATA;

It's verbose and easy to forget.

So developers didn't do it, and that's why we still have 0x80004005 (and why I'm pulling my hair out).

Note that if the developer is conscientious and does things correctly, the .NET runtime will call GetErrorInfo to retrieve the error message and will use its description to create a COMException object that will then be thrown.

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