• e-t172 <idontlikespam nospam.com> Feb 26 2007
• Frits van Bommel <fvbommel REMwOVExCAPSs.nl> Feb 26 2007
• e-t172 <idontlikespam nospam.com> Feb 26 2007
• Ary Manzana <ary esperanto.org.ar> Feb 26 2007
• Frits van Bommel <fvbommel REMwOVExCAPSs.nl> Feb 26 2007

e-t172 <idontlikespam nospam.com> writes:

Hi,

(I'm french, sorry for my bad english)

The following doesn't compile :

import std.stdio;

void bar(void* str)
{
	writefln(cast(char[]) str);
}

void main()
{
	char[] foo;

	foo = "Hello world";

	bar(cast(void*) foo);
}

$ dmd void.d
void.d(5): Error: e2ir: cannot cast from void* to char[]

How should I write it to make it work ?

Frits van Bommel <fvbommel REMwOVExCAPSs.nl> writes:

e-t172 wrote:
 Hi,
 
 (I'm french, sorry for my bad english)
 
 The following doesn't compile :
 
 import std.stdio;
 
 void bar(void* str)
 {
     writefln(cast(char[]) str);
 }
 
 void main()
 {
     char[] foo;
 
     foo = "Hello world";
 
     bar(cast(void*) foo);
 }
 
 $ dmd void.d
 void.d(5): Error: e2ir: cannot cast from void* to char[]
 
 How should I write it to make it work ?


<obvious>
Remove the casts and change the argument type of bar to char[]:
---
import std.stdio;

void bar(char[] str)
{
     writefln(str);
}

void main()
{
     char[] foo;

     foo = "Hello world";

     bar(foo);
}
---
</obvious>


Alternatives:

Arrays need a length, which you could also pass separately:
---
import std.stdio;

void bar(size_t length, void* str)
{
     writefln((cast(char*) str)[0 .. length]);
}

void main()
{
     char[] foo;

     foo = "Hello world";

     bar(foo.length, cast(void*) foo);
}
---


If you insist on passing a C-style string in a void* :
---
import std.stdio;
import std.string;

void bar(void* str)
{
     // Convert back to char[] and write to console
     writefln(toString(cast(char*) str));
}

void main()
{
     char[] foo;

     foo = "Hello world";

     // Ensure presence of 0-terminator
     // (This is not necessary for string literals in current DMD
     // versions, but relying on this is a very bad habit. Also, it
     // would break if you ever try to pass a string not directly
     // initialized by a string literal)
     bar(toStringz(foo));
}
---

e-t172 <idontlikespam nospam.com> writes:

Frits van Bommel a écrit :
 Arrays need a length, which you could also pass separately:
 ---
 import std.stdio;
 
 void bar(size_t length, void* str)
 {
     writefln((cast(char*) str)[0 .. length]);
 }
 
 void main()
 {
     char[] foo;
 
     foo = "Hello world";
 
     bar(foo.length, cast(void*) foo);
 }
 ---


Thanks :)

Ary Manzana <ary esperanto.org.ar> writes:

e-t172 escribió:
 Hi,
 
 (I'm french, sorry for my bad english)


I've seen a lot of people saying this same phrase. I think you should 
not say that. Most of the native english speakers doesn't make even a 
little effort to learn other languages, so why you should say sorry?

Frits van Bommel <fvbommel REMwOVExCAPSs.nl> writes:

Ary Manzana wrote:
 e-t172 escribió:
 Hi,

 (I'm french, sorry for my bad english)


 I've seen a lot of people saying this same phrase. I think you should 
 not say that. Most of the native english speakers doesn't make even a 
 little effort to learn other languages, so why you should say sorry?


In fact, on some sites I read I've seen people claiming to be native 
English speakers with seemingly worse English skills than the average 
person using such a phrase. :)