I was thinking a bit lower level than that but yeah, I guess you get my point. I spent a day with a bug that I found in OpenCV (a computer vision/machine learn

I was thinking a bit lower level than that but yeah, I guess you get my point. I spent a day with a bug that I found in OpenCV (a computer vision/machine learning library) that spooks me to this day. How it works internally is that for images to be processed you create a header (with usual image header info) which contains a pointer to the actual image data. There are two ways to do it: one you create the header and then create the image data separately and the other you create the image all in one go. I ended up in a situation where the image (it was going through a couple of different filtering algorithms) would get processed and be displayed regardless of whether or not I had set the pointer to the image data. That image data was already in memory since it was getting read from disk in a separate step, but there was really no way for the library to know its location in memory. I spent a day trying to sort out what was going on -- and threw my own schedule -- because I had to assume something was seriously wrong and would lead to other unintended consequences. I never did figure out what it was but after a lot of testing I decided it wouldn't cause any other problems (it never did, the library I was writing is still the core of a product I'm selling today). If you don't know it OpenCV is about as mature as a software project can get. It was most likely the best tool for the job I had to tackle. But even with the library's stability and widespread use there was just plain voodoo that set a project I was working on back. Other 3rd party tools can be much worse. I don't do any web stuff but I have had to integrate Facebook Connect into products. Interfacing with Facebook can be a nightmare. Their API changes fairly regularly and the documentation can be a mess. Even using a 4th party, regularly updated, helper library I've seen bugs that took ages to sort out. And that's just talking about integrating 3rd party, hopefully mature, components. I don't care how good you are, writing new code means a lot of testing and debugging. I've never seen new code that didn't introduce some voodoo of its own into a project.