On Fri, 08 Jul 2011 18:59:47 +0100, Walter Bright
<[email protected]> wrote:
On 7/8/2011 4:53 AM, Regan Heath wrote:
On Fri, 08 Jul 2011 10:49:08 +0100, Walter Bright
<[email protected]>
wrote:
On 7/8/2011 2:26 AM, Regan Heath wrote:
Why can't we have the
compiler call it automatically whenever we pass a string, or char[]
to an extern
"C" function, where the parameter is defined as char*?
Because char* in C does not necessarily mean "zero terminated string".
Sure, but in many (most?) cases it does. And in those cases where it
doesn't you
could argue ubyte* or byte* should have been used in the D extern "C"
declaration instead. Plus, in those cases, worst case scenario, D
passes an
extra \0 byte to those functions which either ignore it because they
were also
passed a length, or expect a fixed sized structure, or .. I don't know
what as I
can't imagine another case where char* would be used without it being a
"zero
terminated string", or passing/knowing the length ahead of time.
In the worst case, you're adding an extra memory allocation and function
call overhead (that is hidden to the user, and not turn-off-able). This
is not acceptable when interfacing to C.
This worst case only happens when:
1. The extern "C" function takes a char* and is NOT expecting a "zero
terminated string".
2. The char[], string, etc being passed is a fixed length array, or a
slice which has no available space left for the \0.
So, it's rare. I would guess a less than 1% of cases for general
programming.
And, it *is* turn-off-able. You simply change the extern "C" to use
ubyte*, byte*, or void* (instead of char*). This is arguably a better
definition for this sort of function in the first place.
D is already allocating an extra \0 byte for string constants right?
Yes, but in a way that is essentially free.
Yep, this is essentially free, and calling toStringz automatically would
be almost as free, for 99% of cases. Plus it would "just work" which is a
big deal when you're talking about first impressions etc.
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