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Hm, I was thinking of suggesting that (local buffer) to David, but that's way too bad design considering multithreaded applications.
But having the local buffer in stack (not 'static') is safe; David, is that an option? 

{
	char buffer[80];
	int length = myapi(NULL, 0);
	assert( length <= sizeof(buffer) );
	(void) myapi(buffer, length);

	lua_pushlstring(L, buffer, length);
}
Of course, one can resort to the malloc code, if length turns out to be too big (instead of assertion). 

-asko


Klaus Ripke kirjoitti 4.2.2006 kello 23.19:


On Sat, Feb 04, 2006 at 07:47:19PM +0200, Asko Kauppi wrote:

No, I think not (without patching the Lua C/API, that is).

David Given kirjoitti 2.2.2006 kello 19.44:


I'm trying to wrap a particular API function that writes a string
into a
buffer.

...

I'd like to avoid the temporary buffer. Is there any way of
persuading Lua to
allocate an *uninitialised* string of a particular length on the
stack, and
then giving me a pointer to it so I can fill in that data one's the
string's
been allocated?

Yet there is a standard workaround.

For short strings, which are 99% in most applications,
the overhead of the additional malloc by far outweights the
extra copy.

So you should see substantial speedup by providing a fixed local
buffer of 1K or so a/o using alloca, depending on platform.


best