Does using large libraries inherently make slower code?

Question

I have a psychological tic which makes me reluctant to use large libraries (like GLib or Boost) in lower-level languages like C and C++. In my mind, I think:

Answer 1

You are very right to be worried, especially when it comes to boost. It's not so much due to anyone writing them being incompetent but due to two issues.

1. Templates are just inherently bloated code. This didn't matter as much 10 years ago, but nowadays the CPU is much faster than memory access and this trend continues. I'd almost say templates are an obsolescent feature.

It's not so bad for user code which is usually somewhat practical, but in many libraries everything is defined in terms of other templates or template on on multiple items (meaning exponential template code explosions).

Simply adding in iostream adds about 3 mb (!!!) to your code. Now add in some boost nonsense and you have 30 mb of code if you sinply declare a couple of particularly weird data structures.

Worse, you can't even easily profile this. I can tell you the difference between code written by me and code from template libraries is DRAMATIC but for a more naieve approach you may think you are doing worse from a simple test, but the cost in code bloat will take its tool in a large realworld app.

2. Complexity. When you look at the things in Boost, they are all things that complicate your code to a huge degree. Things like smart pointers, functors, all sorts of complicated stuff. Now, I won't say it's never a good idea to use this stuff, but pretty much all of it has a big cost of some kind. Especially if you don't understand exactly, I mean exactly, what it's doing.

But people rave about it and pretend it has something to do with 'design' so people get the impression it is the way you should do everything, not just some extremely specialized tools that should be used seldom. If ever.