Hear lately I've been listening to Jeff Atwood and Joel Spolsky's radio show and they have been talking about dogfooding (the process of reusing your own code, see Jeff Atwood's blog post). So my question is should programmers use decompilers to see how that programmers code is implemented and works, to make sure it won't break your code. Or should you just trust that programmers code and adapt to it because using decompilers go against everything we as programmers have ever learn about hiding data (well OO programmers at least)?
Note: I wasn't sure which tags this would go under so feel free to retag it.
Edit: Just to clarify I was asking about decompilers as a last resort, say you can't get the source code for some reason. Sorry, I should have supplied this in the original question.
Yes, It can be useful to use the output of a decompiler, but not for what you suggest. The output of a compiler doesn't ever look much like what a human would write (except when it does.) It can't tell you why the code does what it does, or what a particular variable should mean. It's unlikely to be worth the trouble to do this unless you already have the source.
If you do have the source, then there are lots of good reasons to use a decompiler in your development process.
Most often, the reasons for using the output of a decompiler is to better optimize code. Sometimes, with high optimization settings, a compiler will just get it wrong. This can be almost impossible to sort out in some cases without comparing the output of the compiler at different levels of optimization.
Other times, when trying to squeeze the most performance out of a very hot code path, a developer can try arranging their code in a few different ways and compare the compiled results. As a last resort, this may be the simplest way to start when implementing a code block in assembly language, by duplicating the compiler's output.