On 12/16/2016 16:45, John Baldwin wrote: > On Friday, December 16, 2016 08:53:26 PM Dimitry Andric wrote: >> On 16 Dec 2016, at 20:31, Baptiste Daroussin <b...@freebsd.org> wrote: >>> >>> On Fri, Dec 16, 2016 at 01:44:51AM +0000, Conrad E. Meyer wrote: >>>> Author: cem >>>> Date: Fri Dec 16 01:44:50 2016 >>>> New Revision: 310138 >>>> URL: https://svnweb.freebsd.org/changeset/base/310138 >>>> >>>> Log: >>>> vfprintf(3): Add support for kernel %b format >>>> >>>> This is a direct port of the kernel %b format. >>>> >>>> I'm unclear on if (more) non-portable printf extensions will be a >>>> problem. I think it's desirable to have userspace formats include all >>>> kernel formats, but there may be competing goals I'm not aware of. >>>> >>>> Reviewed by: no one, unfortunately >>>> Sponsored by: Dell EMC Isilon >>>> Differential Revision: https://reviews.freebsd.org/D8426 >>>> >>> >>> I really don't think it is a good idea, if used in userland it would be make >>> more of our code difficult to port elsewhere. >> >> Indeed, this is a bad idea. These custom format specifiers should be >> eliminated, not multiplied. :-) >> >> >>> Other than that, it makes more difficult to use vanilla gcc with out >>> userland. >>> and it is adding more complexity to be able to build freebsd from a non >>> freebsd >>> system which some people are working on. >>> >>> Personnaly I would prefer to see those extensions removed from the kernel >>> rather >>> than see them available in userland. >> >> Same here. >> >> >>> Can't we use simple helper function instead? >> >> Yes, please. Just take the snprintb(3) function from NetBSD: >> >> http://netbsd.gw.com/cgi-bin/man-cgi?snprintb+3+NetBSD-current > > In general I agree with something like this instead, but it is quite a bit > more > tedious to use as you have to run it once to determine the length, allocate a > buffer, and then run it again. Calling malloc() for that buffer isn't always > convenient in the kernel (though it should be fine in userland). Having it > live > in printf() itself means the output is generated to the stream without having > to > manage a variable-sized intermediate buffer.
I imagine most callers can simply use a char[sizeof(fmt)+C] on the stack, where C is some constant that I haven't taken the time to calculate, at the risk of making myself look foolish and unprofessional. Eric _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
