[LLVMdev] Any way how to instantiate templates even when it is not necessary for the compilation?

[Nathan Jeffords]

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
> >
> >
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20120508/a70ffa60/attachment.html>