fmemopen

[Roland McGrath]

> That's closer, except I have to be able to rewind and re-read.
> open_memstream's fseek is non-functional.  

Seeking is supposed to work, though I can believe it's never been tested
properly in the libio implementation of open_memstream.  If it's broken,
report the bug.

> Also, I didn't even know about it.  If it isn't documented, I can't find
> out about it, so, basically, it doesn't exist.  :( 

It's in the GNU C Library manual right next to fmemopen.
It's hard to want to help you if you don't even read the manual.

> I am referring to the "bufloc" and "sizeloc" data areas used
> by the open_memstream interface.  With an "fioctl" interface,
> the fmemopen/open_memstream/whatever-else-you-want functions
> can store that information in their own private structures instead
> of relying on the caller to ensure that stable, separate memory is
> available for each invocation of these functions.  It's cleaner.

That's just nonsense.