Using C to talk to C

I've released the first version of a PLaneT package for working with C. It's based on an idea I got from Felix Klock's Scheme Workshop 2008 paper: rather than try to do manual pointer arithmetic based on the current architecture's ABI, you can find out byte offsets of data structures by creating a C program that tells you what they should be. So that's what c.plt allows you to do; using a system-installed C compiler, you can generate a representation of the binary layouts of data structures. Here's a sample interaction:

> (define time.h
   (make-header
     #reader (planet dherman/c/reader) {
         struct tm {
             int tm_sec;
             int tm_min;
             int tm_hour;
             int tm_mday;
             int tm_mon;
             int tm_year;
             int tm_wday;
             int tm_yday;
             int tm_isdst;
         };
     }))
> (define time-abi
   (compile-header time.h
     (system-compiler #:include<> '("time.h") gcc)))
> (layout-size (time-abi 'tm))
36
> (layout-offset (time-abi 'tm) 'tm_sec)
0
> (layout-offset (time-abi 'tm) 'tm_year)
20