virtual template methods

[David Malcolm]

On Wed, 2015-04-15 at 17:20 -0700, Norman Goldstein wrote:
> I have been thinking about a reasonable work-around for virtual template 
> methods.
> The crux boils down to being able to do the following (in the simplest 
> case of a
> single template parameter):
> 
> Input:
> --  An std::type_info
> -- A template global/static function (of one template parameter)
> Output:
> -- An instantiation of the template function with the given type
> 
> Is this the kind of thing that is in the ballpark for gccjit?

If I understand your idea correctly, there are a couple of issues with
using gccjit for it:

(i) gccjit doesn't have any special knowledge of std::type_info at the
moment, and AIUI the latter is implementation-specific.  I guess we'd
need some way to make a gcc_jit_type * from a std::type_info.

(ii) gccjit doesn't have any knowledge of the C++ frontend; and there's
no API yet for the latter.  When you talk about "a template
global/static function (of one template parameter)", where would this
come from?
Note that it's possible to use gccjit in a parameterized way to create
functions; have a function that creates a gcc_jit_function *, passing in
a gcc_jit_type * as a parameter.  An example of doing this can be seen
in the testsuite in 
  gcc/testsuite/jit.dg/test-arith-overflow.c
where we create the equivalent of:
       int
       test_overflow_T_OP (T x, T y, bool *ovf);
for various types T.

Hope this is helpful
Dave