about header file parsing

[David Malcolm]

On Wed, 2019-01-09 at 16:13 +0100, Basile Starynkevitch wrote:
> On 1/9/19 4:03 PM, akrl wrote:
> > Sorry I try to explain it better.
> > I was thinking to a gcc plugin (or potentially something else)
> > that 
> > given a C file produce the libgccjit code necessary to fill a
> > context
> > with what is in the source file.
> 
> That could not work in general, because C has macros (think of the
> `EOF` 
> macro constant in `<stdio.h>`) that have no equivalent in libgccjit. 

Although possibly not working "in general" I think it could work for
most important cases.   A macro in C typically can be handled as either
a client-side function invocation in libgccjit, or as a libgccjit
function.

For example, CPython has various reference-counting macros:

 #define Py_XDECREF(op) do { if ((op) == NULL) ; else Py_DECREF(op); } while (0)

and in my "coconut" JIT-compiler for CPython I implement this as a
libgccjit function:

https://github.com/davidmalcolm/coconut/blob/master/coconut/compiler.py
#L501

(effectively treating it as a static inline function).

> And 
> in practice C macros are very important (and a lot of API for C are 
> using macros, see also macros such as WIFEXITED in wait(2) on some
> Linux 
> system).
> 
> We have to admit that C and libgccjit are different "languages" (even
> if 
> conceptually very close). And a C API is not exactly a set of
> "objects" 
> that libgccjit can handle.

They're not the same, but it is important that libgccjit be able to
interoperate well with C APIs.

Dave