llvm dev - May 2012 - [LLVMdev] Any way how to instantiate templates even when it is not necessary for the compilation?

My gut tells me that if it isn't already available, then it will
be difficult as the instantiation has to occur for the final compilation,
but that must be occurring in a later phase of compilation than the one
where the XML file is generated. Their is also a good chance that the
instantiation depends on information that isn't available until after the
XML file is generated (things like overload candidates found during
argument dependent look-up). I am not very familiar with clang's code or
structure so this is just speculation, perhaps a query on clangs developers
list might give you more insight into what options you may have.

On Tue, May 8, 2012 at 3:22 PM, Ondrej Kolacek <natris1 at gmail.com>
wrote:
> Hello,
> I do not have the code right here but if I understood your question
> correctly, you are asking whether the "generic" structures of the
> template are dumped into xml while the "specialization" is
printed
> incomplete. Yes, xml dump of the structure containing stuff like "this
> template has parameter typename T" is present. But I do not dare to
> use the dump of the template's generic structure for doing the
> template parameter substitution within my code as this looks
> nontrivial, very error prone, and not all the necessary information
> for the substitution is currently available in XML.
>
> I currently plan to try to somehow hack the parser to call the
> function which instantiates templates from some convenient place,
> although whether I will be able to find such a place and the correct
> function I am not certain. This is why I have tried to find some
> alternate solution via this mail.
>
> Ondrej
>
>
> On Tue, May 8, 2012 at 1:03 AM, Nathan Jeffords <blunted2night at
gmail.com>
> wrote:
> > Is the original definition of the template available in the XML file,
not
> > just the reference to the specific instantiations (i.e.
> > IMyEnumerator<int>).
> >
> >
> > On Mon, May 7, 2012 at 12:08 PM, Ondrej Kolacek <natris1 at
gmail.com>
> wrote:
> >>
> >> (another try from different mail account; I hope I was able to
clarify
> >> my issue better. )
> >>
> >> Hello,
> >> I am working on a tool which takes c++ header files of a C++ DLL
and
> >> based on "interfaces" defined in them generates csharp
classes and
> >> glue layer for interop. For analyzing the c++ code I am currently
> >> using clang, which parses the headers and writes output into xml
via
> >> -ast-print-xml (yes, this unfortunately means that it is a very
old
> >> version of clang). I then use these xml files to generate the
csharp
> >> code. Since the header files are written in consistent style, it
works
> >> pretty well.
> >>
> >> But new version of headers contains templates. Nothing fancy,
usually
> >> stuff like:
> >> template <typename T>
> >> IMyEnumerator {
> >> virtual HRESULT GetCurrent(T*item) = 0;
> >> };
> >> class IWhateverInterface {
> >> virtual IMyEnumerator<int> & GetEnumerator() = 0;
> >> };
> >> And here lies the problem - since the template
IMyEnumerator<int> is
> >> only used in this declaration, this template specialization is not
> >> instantiated and the XML does not contain full CXXRecord of the
class.
> >> I however need to know the full structure of the type because I
need
> >> to generate the glue layer for the enumerator.
> >>
> >> It seems to me that this would be quite a common problem for
similar
> >> tools and someone might have stumbled upon it already, and because
of
> >> this I'd like to ask: is there any clean way how to force
> >> instantiation of templates that do not strictly have to be
> >> instantiated? Because if it isn't, this means that I will
either have
> >> to somehow analyze the headers and generate code which forces the
> >> instantiation (which is not really trivial) or try to hack the
code
> >> somehow to force the instantiation (probably possible but
certainly
> >> not pretty).
> >>
> >> NOTE: one example of code which forces the instantiation is
> >> class Dummy : public IMyEnumerator<int>
> >> {
> >> };
> >>
> >> Thank you for any idea,
> >> Ondrej
> >
> >
>
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