The Old New Thing

Understanding the classical model for linking: Sometimes you don’t want a symbol to come along for a ride

January 10, 2013 Jan 10, 2013 01/10/13

Raymond Chen

Continuing our study of the classical model for linking, let's take another look at the trick of taking symbols along for the ride. The technique of taking symbols along for the ride is quite handy if that's what you want, but sometimes you don't actually want it. For example, a symbol taken along for the ride may create conflicts or ...

The enduring cultural fascination with Queen’s Bohemian Rhapsody

January 9, 2013 Jan 9, 2013 01/9/13

Raymond Chen

Bohemian Rhapsody was not part of my world growing up, so I view the continuing cultural fascination with the piece with detached confusion. The hallmark of cultural preoccupation is the fact that the Wikipedia entry deconstructs the piece moment by moment, clocking in at over 2000 words, far in excess of the Wikipedia recommendation of a ...

Understanding the classical model for linking: You can override an LIB with another LIB, and a LIB with an OBJ, but you can’t override an OBJ

January 9, 2013 Jan 9, 2013 01/9/13

Raymond Chen

If you study the classical model for linking, you'll see that OBJ files provided directly to the linker have a special property: They are added to the module even if nobody requests a symbol from them. OBJs bundled into a library are pulled into the module only if they are needed to resolve a needed symbol request. If nobody needs a symbol ...

Understanding the classical model for linking: Taking symbols along for the ride

January 8, 2013 Jan 8, 2013 01/8/13

Raymond Chen

Last time, we learned the basics of the classical model for linking. Today, we'll look at the historical background for that model, and how the model is exploited by libraries. In the classical model, compilers and assemblers consume source code and spit out an OBJ file. They do as much as they can, but eventually they get stuck because ...

Understanding the classical model for linking, groundwork: The algorithm

January 7, 2013 Jan 7, 2013 01/7/13

Raymond Chen

The classical model for linking goes like this: Each OBJ file contains two lists of symbols. Provided symbols: These are symbols the OBJ contains definitions for. Needed symbols: These are symbols the OBJ would like the definitions for. (The official terms for these are exported and imported, but I will use provided and needed ...

What’s the guidance on when to use rundll32? Easy: Don’t use it

January 4, 2013 Jan 4, 2013 01/4/13

Raymond Chen

Occasionally, a customer will ask, "What is Rundll32.exe and when should I use it instead of just writing a standalone exe?" The guidance is very simple: Don't use rundll32. Just write your standalone exe. Rundll32 is a leftover from Windows 95, and it has been deprecated since at least Windows Vista because it violates a lot of ...

Why does my program run really slow or even crash (or stop crashing, or crash differently) if running under a debugger?

January 3, 2013 Jan 3, 2013 01/3/13

Raymond Chen

More than once, a customer has noticed that running the exact same program under the debugger rather than standalone causes it to change behavior. And not just in the "oh, the timing of various operations changed to hit different race conditions" but in much more fundamental ways like "my program runs really slow" or "my program crashes in a ...