When you write an innocent

   char buf[256];
   ....
   printf("buf=%s\n",buf);

You get an

   buf=Error: Access Violation

You need to write

   printf("buf=%s\n",&buf[0]);

to get the code to work correctly.

Of course it's the same with
   fgets(&buf[0],buf.size,c.stdio.stdin);
and dozens of other C functions that take char * (in fact array)
parameters.

This will cost a lot of progammers that are used to C
a lot of time to get used to.

IMHO D should either
  - give a clear error message (and not silently take the char []
    without converting it correctly )
or
  - support the normal array passing semantics for functions that
    are "extern C".

--
Helmut Leitner    leitner@hls.via.at Graz, Austria   www.hls-software.com

In article <3EE2FC42.63A0F747@chello.at>, Helmut Leitner says...
>
>When you write an innocent
>
>   char buf[256];
>   ....
>   printf("buf=%s\n",buf);
>
>You get an
> 
>   buf=Error: Access Violation
>
>You need to write
>
>   printf("buf=%s\n",&buf[0]);
>
>to get the code to work correctly.
>
>Of course it's the same with
>   fgets(&buf[0],buf.size,c.stdio.stdin);
>and dozens of other C functions that take char * (in fact array)
>parameters.
>
>This will cost a lot of progammers that are used to C
>a lot of time to get used to.

To call C functions from Ada you have to do the same thing, explicitly pass the address of buf[0], which is not a bad thing since that clearly states what is going on. The C idiom of array name is equivalent to address of first element should probably not be carried forward into D since it will probably prevent good type checking. I do agree this should be strongly docummented in any language manuals. Remember D is not supposed to be a syntax and semantically compatible with C just easily interfaced. When you use a new language you have to get used to it's syntax and semantics.  A few extra characters for clarity will not hurt anyone.  Welcome to strongly typed languages.

Mark T wrote:
> 
> In article <3EE2FC42.63A0F747@chello.at>, Helmut Leitner says...
> >
> >When you write an innocent
> >
> >   char buf[256];
> >   ....
> >   printf("buf=%s\n",buf);
> >
> >You get an
> >
> >   buf=Error: Access Violation
> >
> >You need to write
> >
> >   printf("buf=%s\n",&buf[0]);
> >
> >to get the code to work correctly.
> >
> >Of course it's the same with
> >   fgets(&buf[0],buf.size,c.stdio.stdin);
> >and dozens of other C functions that take char * (in fact array)
> >parameters.
> >
> >This will cost a lot of progammers that are used to C
> >a lot of time to get used to.
> 
> To call C functions from Ada you have to do the same thing, explicitly pass the address of buf[0], which is not a bad thing since that clearly states what is going on. The C idiom of array name is equivalent to address of first element should probably not be carried forward into D since it will probably prevent good type checking. I do agree this should be strongly docummented in any language manuals. Remember D is not supposed to be a syntax and semantically compatible with C just easily interfaced. When you use a new language you have to get used to it's syntax and semantics.  A few extra characters for clarity will not hurt anyone.  Welcome to strongly typed languages.

I don't mind to write
   fgets(&buf[0],buf.size,c.stdio.stdin);

but silent compilation of
   fgets(buf,buf.size,c.stdio.stdin);
with a resulting runtime error is unacceptable.

--
Helmut Leitner    leitner@hls.via.at Graz, Austria   www.hls-software.com

Seems like another argument for having a true string type...

Sz.

"Helmut Leitner" <helmut.leitner@chello.at> wrote in message news:3EE2FC42.63A0F747@chello.at...
> When you write an innocent
>
>    char buf[256];
>    ....
>    printf("buf=%s\n",buf);
>
> You get an
>
>    buf=Error: Access Violation
>
> You need to write
>
>    printf("buf=%s\n",&buf[0]);
>
> to get the code to work correctly.

To get it to work best in D, write it as:

    printf("buf = %.*s\n", buf);


> Of course it's the same with
>    fgets(&buf[0],buf.size,c.stdio.stdin);

It shouldn't be, as fgets() has a parameter prototype for the first argument. D will implicitly convert an array to a pointer, so this should work fine:

    fgets(buf, buf.length, c.stdio.stdin);

It's only an issue with varargs ... parameters.

>   - support the normal array passing semantics for functions that
>     are "extern C".

Since printf is extern C, that would make it impossible to print D arrays using it.

Walter wrote:
> > Of course it's the same with
> >    fgets(&buf[0],buf.size,c.stdio.stdin);
> 
> It shouldn't be, as fgets() has a parameter prototype for the first argument. D will implicitly convert an array to a pointer, so this should work fine:
> 
>     fgets(buf, buf.length, c.stdio.stdin);

Fine that it's working now, it didn't with my last version (0.61).

--
Helmut Leitner    leitner@hls.via.at Graz, Austria   www.hls-software.com