• Abby (7/7) Mar 11 2020 What is the proper way to get char* from string which is used in
• 9il (4/11) Mar 11 2020 1. Yes.
• 9il (16/27) Mar 11 2020 3. You can use mir-algorithm for simplicity and speed
• rikki cattermole (3/13) Mar 11 2020 String literals are null terminated so you can pass them straight to C.

Abby <loniro7678 twit-mail.com> writes:

What is the proper way to get char* from string which is used in 
c functions? toStringz does returns:

/usr/include/dmd/phobos/std/array.d(965,49): Error: TypeInfo 
cannot be used with -betterC

and I think string.ptr is not safe because it's not zero 
termined. So what should I do? realloc each string with /0?

Thank you for your help

9il <ilyayaroshenko gmail.com> writes:

On Wednesday, 11 March 2020 at 16:07:06 UTC, Abby wrote:
 What is the proper way to get char* from string which is used 
 in c functions? toStringz does returns:

 /usr/include/dmd/phobos/std/array.d(965,49): Error: TypeInfo 
 cannot be used with -betterC

 and I think string.ptr is not safe because it's not zero 
 termined. So what should I do? realloc each string with /0?

 Thank you for your help

1. Yes.
2. A compile-time known or constants always contain trailing zero.

static immutable "some text"; // contains \0 after the data.

9il <ilyayaroshenko gmail.com> writes:

On Wednesday, 11 March 2020 at 16:10:48 UTC, 9il wrote:
 On Wednesday, 11 March 2020 at 16:07:06 UTC, Abby wrote:
 What is the proper way to get char* from string which is used 
 in c functions? toStringz does returns:

 /usr/include/dmd/phobos/std/array.d(965,49): Error: TypeInfo 
 cannot be used with -betterC

 and I think string.ptr is not safe because it's not zero 
 termined. So what should I do? realloc each string with /0?

 Thank you for your help


3. You can use mir-algorithm for simplicity and speed

----
/+dub.sdl:
dependency "mir-algorithm" version="~>3.7.18"
+/
import mir.format;
import core.stdc.stdio;

void main() {
     printf("some_string %s", (stringBuf() << "other_string" << 
"\0" << getData).ptr);
}
----

stringBuf() uses stack if the inner string fits into it. So, It 
is a mutch master than malloc/free. However, in this case C 
function should return pointer ownership to the caller.

rikki cattermole <rikki cattermole.co.nz> writes:

On 12/03/2020 5:07 AM, Abby wrote:
 What is the proper way to get char* from string which is used in c 
 functions? toStringz does returns:
 
 /usr/include/dmd/phobos/std/array.d(965,49): Error: TypeInfo cannot be 
 used with -betterC
 
 and I think string.ptr is not safe because it's not zero termined. So 
 what should I do? realloc each string with /0?
 
 Thank you for your help

String literals are null terminated so you can pass them straight to C.

toStringz will of course not work as that relies on the GC.