Dude! Where's my string constant?

[Frits van Bommel]

kris wrote:
> Does D have a compile-time string constants? One that doesn't wind up in 
> the obj file when it is unused?
> 
> const char[] Foo = "foo";
> 
> Apparently resides in the object file, used or not. Just like const int 
> does. For true compile-time integer constants, we're supposed to use 
> enum -- but what of strings? Enum currently doesn't like char[] :)
> 
> Suggestions for faking it include:
> 
> * char[] Foo() { return "foo"; }

Only works if *no* string constant in the module is used. They're all 
put into .rodata, which is only thrown away if it's not referenced *at 
all*.[1]

> * template Foo { const Foo="foo"; }

This string will not be created until Foo is instantiated, and is put 
into a separate linkonce section (which can be removed if unused)[1]. 
Good find :).

Note: this won't happen if the member is declared char[], it needs to be 
the (automatically-deduced) static array.

> The former *should* get removed by the linker as unused, while the 

It isn't necessarily, as noted above.

> latter apparently gets eliminated by way of lack-of-expansion.

Yep.

> However, going to these lengths is surely counter-intuitive?

Yes it is. What happens for the second one when instantiated should 
really happen by default for all strings (i.e. be put into separate 
sections).


[1]: Usual disclaimer: on Linux, using ld --gc-sections. I know not of 
OMF & optlink :P.