One option could be to create a small shared library that you compile for each platform that just exported the member offsets... https://www.embedded.com/design/prototyping-and-development/4024941/Learn-a-new-trick-with-the-offsetof--macro
You first FFI to that read struct member offsets and dynamically create the definitions for your target library. I haven't tried it in practice. cheers -ben P.S. Occasionally I dream about compilers being able to embed a pre-compiled header declaration block in the library for FFI users to iterate... https://clang.llvm.org/docs/PCHInternals.html#declarations-block On Sun, 2 Dec 2018 at 17:04, Alistair Grant <akgrant0...@gmail.com> wrote: > Hi Phil and Esteban, > > Thanks for your replies. > > I've realised that I badly worded my question. By "opaque" I meant that > it is difficult to determine the underlying type of the > variables, but I still want to be access the values of typeA and typeB > in my example structure. > > Phil, I had a look through your XMPP code, if it does show an example of > actually retrieving a structure member such as "typeA" in my example, my > apologies and please let me know where it is. > > Thanks again, > Alistair > > > On Fri, 30 Nov 2018 at 23:46, Esteban Lorenzano <esteba...@gmail.com> > wrote: > > > > On 30 Nov 2018, at 19:50, phil--- via Pharo-users < > pharo-users@lists.pharo.org> wrote: > > > > From: "p...@highoctane.be" <p...@highoctane.be> > > Subject: Re: [Pharo-users] UFFI and opaque(ish) types > > Date: 30 November 2018 at 19:50:03 CET > > To: Any question about pharo is welcome <pharo-users@lists.pharo.org> > > > > > > Inherit from FFIOpaqueObject > > > > + initialize TypeMap > > > > I have a few here: > > > > https://github.com/Pharophile/XmppTalk > > > > > https://github.com/Pharophile/XmppTalk/tree/master/packages/XmppTalk-ExternalStructures.package > > > https://github.com/Pharophile/XmppTalk/blob/master/packages/XmppTalk-LibStrophe.package/StropheLib.class/class/initializeTypeMap.st > > > > HTH > > Phil > > > > > > Yes, as he says/shows :) > > > > Esteban > > > On Fri, Nov 30, 2018 at 2:39 PM Alistair Grant <akgrant0...@gmail.com> > wrote: > >> > >> How are opaque(ish) types normally handled in UFFI (or FFI)? > >> > >> E.g. if I want to use libstuff which defines the following structure: > >> > >> struct stuffstruct { > >> typeA a; > >> typeB b; > >> } stufftype; > >> > >> > >> I might know they're integers, but not the size, signed vs. unsigned, > >> etc. > >> > >> The definitions of typeA and typeB are buried in multiple layers of > >> header files, dependent on #if tests, can be different sizes on > >> different platforms (e.g. Linux vs. MacOS), etc.? > >> > >> Is this documented somewhere? > >> > >> Thanks, > >> Alistair > >
