Passing string literals to C

[Daniel Kozák via Digitalmars-d-learn]

V Wed, 31 Dec 2014 11:19:35 +0000
Laeeth Isharc via Digitalmars-d-learn
<digitalmars-d-learn at puremagic.com> napsáno:

> Argh - no way to edit.
> 
> What's best practice here?
> 
> D strings are not null-terminated.
> ===
> cpling.c
> 
> char* cpling(char *s)
> {
>    s[0]='!';
>    return s;
> }
> ===
> dcaller.d
> 
> extern(C) char* cpling(char* s);
> 
> void callC()
> {
>    writefln("%s",fromStringz(cpling("hello\0")));
> }
> 
> or
> 
> void callC()
> {
>    writefln("%s",fromStringz(cpling(toStringz("hello"))));
> }
> 
> ===
> 
> am I missing a better way to do this?

First I am not sure, but you do not need to call fromStringz in this
case. Next in this example you even not need to call toStringz, because
D string literals are null-terminated. But generally it is better to
use toStringz when need pass D strings to C code.

Important Note: When passing a char* to a C function, and the C
function keeps it around for any reason, make sure that you keep a
reference to it in your D code. Otherwise, it may go away during a
garbage collection cycle and cause a nasty bug when the C code tries to
use it.