• Bauss (2/2) Dec 13 2016 If a function is only called during compile-time will it be
• Nicholas Wilson (10/12) Dec 14 2016 It depends. When linking unused functions can be removed by
• Johan Engelen (14/16) Dec 14 2016 With "available at runtime", I guess you mean "will it be part of

Bauss <jj_1337 live.dk> writes:

If a function is only called during compile-time will it be 
available at runtime?

Nicholas Wilson <iamthewilsonator hotmail.com> writes:

On Wednesday, 14 December 2016 at 07:15:08 UTC, Bauss wrote:
 If a function is only called during compile-time will it be 
 available at runtime?

It depends. When linking unused functions can be removed by 
-gc-sections, but only when linking an executable.

But obviously if you use it at runtime then the linker won't 
remove it. If you want to ensure that it never gets called at 
runtime, put a `assert(__ctfe);` at the beginning of the function.

There was a discussion some time ago about having an attribute(?) 
to disable codegen for particular functions (e.g. code for 
generating string for string mixins), but i'm not sure what 
became of that.

Johan Engelen <j j.nl> writes:

On Wednesday, 14 December 2016 at 07:15:08 UTC, Bauss wrote:
 If a function is only called during compile-time will it be 
 available at runtime?

With "available at runtime", I guess you mean "will it be part of 
the object file". In that case: yes. Because even if a function 
is _never_ called, it will be part of the object file (it must 
be).

For templated functions, the answer is not so easy. Templates 
that are only instantiated during CTFE are usually also emitted 
into the object file. But, when importing a templated function 
from another module, the template instantiation is not emitted to 
the object file if the compiler deduces that the instantiation is 
already emitted in the object file result of compiling the 
imported module (to avoid unnecessary duplicate instantiations 
across compilation units).

-Johan