The Yardarm is a type introspection library for C. It gives you enough rope to provide descriptions of the C types used in your program, which you can access during compilation or at runtime. Think of it as a C version of C++'s RTTI or Java's reflection API.
A common complaint about C is the amount of boilerplate code that you have to write. Often, this boilerplate is completely uninteresting "turn the crank" code that only depends on the stucture of one of your C types. One way around this problem is to use code generation to automatically produce all of the annoying boilerplate from a nicer, more conside description of the type.
Another option is to provide a single, generic implementation of the boilerplate code, that would work with any type. To do this, the generic implementation would need information, at runtime, about the types involved. All the usual benefits of type introspection, but for C.
Isn't this just libffi?
This might sound awfully familiar to libffi.
After all, libffi provides
ffi_type, which is used to describe the types of
values passed around by functions. However,
ffi_type does not contain all of
the information we might need to know about a C type. Since libffi is focused
on calling conventions and ABIs,
ffi_type focuses on just the information
needed to successfully use a value of that type as a parameter or result of a
Yardarm and libffi type descriptors are orthogonal. In fact, one of the (more
immediate) plans for Yardarm is to allow you to automatically generate
ffi_type descriptors from a Yardarm type descriptor.
Coming soon. The API is in flux; check back in a few days.