Many people don't realise just how much the C99 standard library offers over the previous version (C89). The latest Norcroft C compiler from RISC OS Open supports all the significant features of C99, and hence the (excellent) "C-version5" manual by Neil Bingham has been rendered sadly obsolete.
Rather than trying to create a new manual from scratch, I decided to extract information from the standard library's header files, as the documentation there is extensive (and, you would hope, definitive). This means that these manuals are released under the terms of the RISC OS licence which is available to view here
Note that even though I describe this as a manual for the C99 standard library, I've also included information from two RISC OS specific header files, namely kernel.h and swis.h. However only the documentation for the _swi and _swix functions is included from swis.h - this is not intended to be a SWI reference manual.
The manual is available in two formats, StrongHelp and HTML. The StrongHelp version has a few extra notes, added by me, but they are essentially identical in terms of content. The StrongHelp manual also supports keyword lookup from a suitable editor (eg Zap, StrongEd).
This is very much a work in progress, so please report any problems to me. My email address is in the ReadMe file.
New - I've now released the tool I use to create the manual. It's called MakeHelp (original, huh), and can be found here.
Download manual in StrongHelp format (v 0.02 last updated 22 Dec 2011)
Download manual in HTML format (last updated 20 Dec 2011)