On 08/20/2016 05:18 AM, Trevor Saunders wrote:
Patch #5 and beyond: Further optimization work.
As one of the next steps I'd like to make this feature available
to user-defined sprintf-like functions decorated with attribute
format. To do that, I'm thinking of adding either a fourth
(optional) argument to attribute format printf indicating which
of the function arguments is the destination buffer (to compute
its size), or perhaps a new attribute under its own name. I'm
actually leaning toward latter since I think it could be used
in other contexts as well. I welcome comments and suggestions
on this idea.
Whichever we think will be easier to use and thus encourage folks to
annotate their code properly :-)
So, sort of related I've been thinking about writing C++ string building
classes some lately. Where you'd have a fixed length buffer and a
pointer to the next buffer (so a degenerate rope with only one side of
the tree). One use case for such a thing is building up strings of
assembly to output in gcc. however one somewhat awkward bit is that we
often format assembly with printf, which isn't really great for this use
case, because you need to deal with the case the current buffer only has
space for part of the string you are formatting. So it would be nice to
have something like an interuptable printf that tells you where in the
string it stopped formatting, and allows you to continue from there with
a new buffer.
glibc provides fopencookie, which can be used to print directly to a
custom stream. I don't know if it would provide any speed gains because
of the internal complexities of libio.
It could be emulated using snprintf and a temporary buffer for non-glibc
systems.
Florian
