When does template instantiation bloat matter in practice?

Question

It seems that in C++ and D, languages which are statically compiled and in which template metaprogramming is a popular technique, there is a decent amount of concern about t

Answer 1

There's little problem in C++, because the amount of template stuff you can do in C++ is limited by their complexity.

In D however ... before CTFE (compile-time function evaluation) existed, we had to use templates for string processing. This is also the reason big mangled symbols are compressed in DMD - the strings used as template arguments become part of the mangled symbol names, and when instantiating templates with longer segments of code (for instance) the resulting symbol sizes would spectacularly explode the object format.

It's better nowadays. But on the whole, templates still cause a lot of bloat for a simple reason - they parse faster and are more powerful than in C++, so people naturally use them a lot more (even in cases that technically wouldn't need templates). I must admit I'm one of the prime offenders here (take a look at tools.base if you like, but be sure to keep a barf bag handy - the file is effectively 90% template code).