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From: "dblaikie at gmail dot com" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug symtab/17272] DW_TAG_GNU_template_parameter_pack
Date: Mon, 11 Dec 2023 07:28:44 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D17272

--- Comment #18 from David Blaikie <dblaikie at gmail dot com> ---
(In reply to Hannes Domani from comment #17)
> (In reply to David Blaikie from comment #16)
> > For types you can't have more than one pack, I think:
> > $ clang++-tot -std=3Dc++2a pack_type.cpp=20
> > pack_type.cpp:1:22: error: template parameter pack must be the last tem=
plate
> > parameter
> >     1 | template<typename... T1s, typename... T2s>
> >       |                      ^
> > 1 error generated.
> >=20
> > But you can have multiple packs in a function template - and I think it=
'd be
> > good to represent it correctly - since there can be two functions, for
> > instance, with the same parameters but packed differently (eg:
> > `template<typename... T1s, typename ... T2s> void f1();` you could have
> > `f1<int>` where the int is in the first pack (and the second pack is em=
pty)
> > or the other way around, and those are distinct overloads)
>=20
> Could you share an example where the 2nd pack is not empty, because I cou=
ld
> not figure out how to do it?

I don't think you can explicitly specify such arguments, they can only be
provided via template argument deduction, like this example:

https://godbolt.org/z/377YT7dfb

Notice that the two `f1` calls call distinct functions:
  _Z2f1IJEJiEEv2t1IJDpT_EES0_IJDpT0_EE
  _Z2f1IJiEJEEv2t1IJDpT_EES0_IJDpT0_EE
or, demangled:
  void f1<, int>(t1<>, t1<int>)
  void f1<int>(t1<int>, t1<>)

--=20
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