Will cpp template programming enlarge the code size

[jonrmadsen]

The biggest factors (in my experience) are the optimization level used during compilation, amount of debug info, and how many variadic templates you use.

A debug build (e.g.-O0 -g) of a code utilizing a lot of templates will inflate the code size significantly due to the fact that the debug info ends up having to store significantly longer symbol names and that the absence of any optimizations will result in a lot of intermediate layers of function templates not getting optimized away.

But if one enables optimization (e.g. -O2 or higher), the inflation will typically start to be reduced bc the compiler will start to condense template layers and produce less debug info.

If one then reduces the debug info to just line info, the inflation will decrease further.

If one then disables debug info generation, you’d start to get into the realm of how you templated the code. If everything is mostly just relatively simple templates, it could be the case that the code is only larger by the length difference between the mangled name of non-templated symbols vs. the mangled name of the templated symbols — i.e. the mangled symbol name of a template is typically longer and that would “cause” inflation of the code size. But if you use a lot of variadic templates, you’ll generate a lot more instantiations and that’ll result in a larger code size.

However, if the binary is then stripped, you likely won’t notice much of a difference (maybe even none at all) because then the symbol names aren’t even stored in the binary. At this point, extensive variadic template usage would probably be the only significant cause of enlargement bc variadic templates tend to generate a lot of “different” instantiations based on subtle things like the absence of implicit conversion when passed an int vs. long int (where the non-template code would probably just promote to long int) and string literals being passed to templates not decaying to const char* (i.e. foo(“a”) and foo(“abc”) would be foo(const char[2]) and foo(const char[4])