update page 2 - Dave's Blog

Bug Spotting: Smart pointers and parameter evaluation order

The following code works fine. I have a ccomptr named resolvedUri and I want to update its hostname so I do the following:

        CreateIUriBuilder(resolvedUri, 0, 0, &builder);
        builder->SetHost(host);
        builder->CreateUri(0xFFFFFFFF, 0, 0, &resolvedUri);

But the following similar looking code has a bug:

    ResolveHost(resolvedUri, &resolvedUri);

The issue is that doing &resolvedUri gets the address of the pointer but also clears out the pointer due to the definition of my smart pointer class:

    operator T**()  
    {  
        T *ptrValue = mPtrValue;
        mPtrValue->Release();
        mPtrValue = NULL;
        return &ptrValue;
    }

In C++ there’s no guarantee about the order in which parameters for a function or method are evaluated. In the case above, &resolvedUri clears out the ccomptr before evaluating resolvedUri.Get() and so ResolveHostAlias gets a nullptr.

An interesting and related thread on stack overflow on undefined behavior in C++.

WPAD Server Fiddler Extension Update v1.0.1

As it turns out the WPAD Server Fiddler Extension I made a while back actually has a non-malicious purpose. Apparently its useful for debugging HTTP on the WP7 phone (or so I'm told). Anyway I took some requests and I've fixed a few minor bugs (start button not updating correctly), changed the dialog to be a Fiddler tab so you can use it non-modally, and the WPAD server is now always off when Fiddler starts.

Encode-O-Matic: Guess Encoding

I've just updated Encode-O-Matic with a Guess Input Encoding feature. When you start Encode-O-Matic or when you use the 'Guess Input Encoding' menu item from the 'Tools' menu, Encode-O-Matic will try out various combinations of encodings and guess at which set seem to apply to your input. For instance given the following text, Encode-O-Matic will correctly guess that it is percent encoded, base64 encoded, deflate compressed text:

S%2BWqUEhLLMoFUulFpXnZQLogMa%2BkmCuPqxzILk%2FMyeHK4QIA

Encode-O-Matic Update: Compression, Hex View, Quick Show Output

I've just put up an update for Encode-O-Matic with the following improvements:

• Hex editor: the output and input views can now be switched between a UTF8 textbox view and a hex editor view. This is built using the free Be.HexEditor.
• Compression: I've added the .NET GZip, deflate, and inflate streams to the list of supported encodings.
• Quick Show Output: There are now 'Show Output' radio buttons next to each encoding in the encoding stack. Clicking on them changes the output view to show the output from that encoding in the stack. This lets you easily jump between different parts of your encoding process. Adding or removing an encoding to the stack resets the view.
• Minor visuals improvement: added app icon, changed buttons with one word symbols to command names.

Thought Experiments and Design Principles

Raymond Chen has some thought experiments useful for discovering various kinds of stupidity in software design:

• What if two programs did this?
• Who says there's only one?
• Imagine if this were possible. / Imagine if things actually worked that way.

Tim Berners-Lee's principles of Web design includes my favorite: Test of Independent Invention. This has a thought experiment containing the construction of the MMM (Multi-Media Mesh) with MRIs (Media Resource Identifiers) and MMTP (Muli-Media Transport Protocol).

The Internet design principles (RFC 1958) includes the Robustness Principle: be strict when sending and tolerant when receiving. A good one, but applied too liberally can lead to interop issues. For instance, consider web browsers. Imagine one browser becomes so popular that web devs create web pages and just test out their pages in this popular browser. They don't ensure their pages conform to standards and accidentally end up depending on the manner in which this popular browser tolerantly accepts non-standard input. This non-standard behavior ends up as de facto standard and future updates to the standard essentially has had decisions made for it.

Dave's Blog Entries Last Year

Inspired by one of Penn's (of Penn & Teller) articles in which he mentions he has his computer tell him what he wrote in his journal that day the previous year, I've wanted to implement a similar thing with my blog. Now that, as I mentioned previously, I've updated my blog such that its much easier to implement search and such, I've added date range filtering to my site's search. So now I can easily see what on Delicious and my blog I was doing last year.

I've also otherwise updated search on this site. You can now quote terms to match an entire string, stick 'tag:' in front of a term to only match that term against tags as opposed to the title and body of the entry as well, and you can stick '-' in front of a term to indicate that it must not be found in the entry.

Blog Layout and Implementation Improvements

I've redone my blog's layout to remind myself how terrible CSS is -- err I mean to play with the more advanced features of CSS 2.1 which are all now available in IE8. As part of the new layout I've included my Delicious links by default but at a smaller size and I've replaced the navigation list options with Technical, Personal and Everything as I've heard from folks that that would actually be useful. Besides the layout I've also updated the back-end, switching from my handmade PHP+XSLT+RSS/Atom monster to a slightly less horrible PHP+DB solution. As a result everything should be much much faster including search which, incidentally, is so much easier to implement outside of XSLT.