• James Dunne <jdunne4 bradley.edu> Mar 08 2005
• =?ISO-8859-1?Q?Anders_F_Bj=F6rklund?= <afb algonet.se> Mar 08 2005
• "Charles" <cee-lo green.com> Mar 09 2005
• "Unknown W. Brackets" <unknown simplemachines.org> Mar 10 2005
• =?ISO-8859-1?Q?Anders_F_Bj=F6rklund?= <afb algonet.se> Mar 10 2005
• Stewart Gordon <smjg_1998 yahoo.com> Mar 10 2005

James Dunne <jdunne4 bradley.edu> writes:

As long as a warning system is being worked on, it'd be nice if the compiler let
me know if I was passing in a char[] for a char* argument to an extern 
(C) function.

I just ran into this doing some DerelictSDL programming.  Very strange bug, and
I didn't notice it since I was so convinced I was writing "Super C" code. :-)
Forgot about toStringz().

Regards,
James Dunne

=?ISO-8859-1?Q?Anders_F_Bj=F6rklund?= <afb algonet.se> writes:

James Dunne wrote:

 As long as a warning system is being worked on, it'd be nice if the compiler
let
 me know if I was passing in a char[] for a char* argument to an extern 
 (C) function.


Unless it's a string literal, right ? Since those are 0-terminated in D,
and since you would get a ton* of warnings when using C stuff otherwise.

--anders

* well, mostly from printf probably, but as long as that is in object...

"Charles" <cee-lo green.com> writes:

char [] used to be automatically converted to char* when passing them to
functions which expect char *.  I think still ?

Charlie

"James Dunne" <jdunne4 bradley.edu> wrote in message
news:d0m54o$1do0$1 digitaldaemon.com...
 As long as a warning system is being worked on, it'd be nice if the


 me know if I was passing in a char[] for a char* argument to an extern
 (C) function.

 I just ran into this doing some DerelictSDL programming.  Very strange


 I didn't notice it since I was so convinced I was writing "Super C" code.


 Forgot about toStringz().

 Regards,
 James Dunne

"Unknown W. Brackets" <unknown simplemachines.org> writes:

The idea is, if you have a function:

extern (C) void f(char* text);

And you pass it a string, like so:

f(char_array);

You may be doing this in error; it may be that you wanted to use:

f(toStringz(char_array));

Or similar.  Personally, I think this is unnecessary.  If I was really 
worried, I'd write a wrapper (which better be inlined!!) to toStringz() 
it and take a char[] array anyway, but only if I were so worried.

-[Unknown]


 char [] used to be automatically converted to char* when passing them to
 functions which expect char *.  I think still ?
 
 Charlie

=?ISO-8859-1?Q?Anders_F_Bj=F6rklund?= <afb algonet.se> writes:

Unknown W. Brackets wrote:

 char [] used to be automatically converted to char* when passing them to
 functions which expect char *.  I think still ?




 The idea is, if you have a function:
 
 extern (C) void f(char* text);


The usual example here being the venerable printf,
which gets passed D string literals (that are char[])
which Walter likes so much that it goes in object.d,
and other such C functions from the C standard library

And to make these easier to use, char[] can be converted
automatically to char* and they are declared as "char*"
instead of as ubyte* or byte* which would be the *proper*
declaration unless they really accept UTF-8 code units...

Otherwise, calling C functions would be quite a hassle ?
(which could arguably be a good thing, promoting writef)

 And you pass it a string, like so:
 
 f(char_array);


If you really *want* to do this, you should probably
use char_array.ptr which is a neat way to access it ?

Makes it clear that you want to get at the raw data,
and will worry about any zero-termination yourself.

  > You may be doing this in error; it may be that you wanted to use:
 
 f(toStringz(char_array));


Which would probably be the most safe approach, too...
(explicitly doing a ~ "\0", like that std routine does)

Or you could use char_array.length and char_array.ptr,
like the "%.*s" approach to printf does (implicitly) ?

--anders

Stewart Gordon <smjg_1998 yahoo.com> writes:

Charles wrote:
 char [] used to be automatically converted to char* when passing them to
 functions which expect char *.  I think still ?



Therein lies the problem.  It's too easy to pass a non-null-terminated 
string to a C function.

I've just been reminded of this....

----------
These two strings walk into a bar and sit down. The bartender says, "So 
what'll it be?"

The first string says, "I think I'll have a beer quag fulk boorg 
jdk^CjfdLk jk3s d#f67howe%^U r89nvy~~owmc63^Dz x.xvcu"

"Please excuse my friend," the second string says, "He isn't 
null-terminated."
----------

But it predates D by about nine years :-(

Stewart.

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