More automated interfacing of D with C codebases

[Brad Lanam]

On Monday, 22 October 2012 at 06:28:12 UTC, Jacob Carlborg wrote:
> On 2012-10-21 21:45, timotheecour wrote:
>> Manually porting of C/C++ libraries shouldn't be the way to go 
>> (a
>> major problem being when said library gets updated, human 
>> errors,
>> porting to different architectures etc).
>
> SWIG requires some kind of interface files, which I assume one 
> must have to manually write. Then what's the difference?

Huge difference.  It's not necessary to figure out corresponding 
type sizes on every system.  I only need to figure out what needs 
to be in there.  And once all the work of creating the interface 
file is done, the work of porting to another architecture or 
operating system or compiler is much reduced.

It's not necessary to figure out which api calls are macros on 
arch XYZ or are simply not there:

cdcl Tcl_IncrRefCount
clib Tcl_IncrRefCount
# if Tcl_IncrRefCount is not defined as a library call, search 
for the macro.
if lib_Tcl_IncrRefCount ! _clib_Tcl_IncrRefCount
  cmacro Tcl_IncrRefCount tcl.h void 'Tcl_Obj *'
endif

My example Tck/Tk conversion doesn't handle 8.6, but the effort 
to add it will be very minimal.  All of the hard work of 
discovering the needed typedefs has been done.

> [...]
> I don't think SWIG is the right approach because:
>
> * You have to create these interface files
> * It seem to not handle all code

I don't know SWIG, but the idea is the same for my tool.

If you try to automate processing of the pre-processed headers, 
all of the included system headers will be processed and too much 
that isn't needed will be output. The included system definitions 
will conflict with D definitions.

I'm not sure that handling *all* code is necessary.  How often do 
you see
this sort of thing in C code?
     _XPrivate .private9, .private10;
Rather than spend effort on handling *every* possible obscure 
C/C++/ObjC construct, it's easier to simply handle those in the 
interface file.

Other constructs that are more common can be added to SWIG or to 
my tool.
They're both open source.

   -- Brad