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* [Bug c++/96719] New: non-standard handling of alias templates used as template template arguments
@ 2020-08-20 1:16 richard-gccbugzilla at metafoo dot co.uk
2020-08-20 7:49 ` [Bug c++/96719] " redi at gcc dot gnu.org
0 siblings, 1 reply; 2+ messages in thread
From: richard-gccbugzilla at metafoo dot co.uk @ 2020-08-20 1:16 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96719
Bug ID: 96719
Summary: non-standard handling of alias templates used as
template template arguments
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: richard-gccbugzilla at metafoo dot co.uk
Target Milestone: ---
template<typename T, typename U = T> struct A { using type = U; };
template<typename V, typename W = float> using B = A<V, W>;
template<template<typename...> class Z> struct Q {
using type = typename Z<int>::type;
};
Here, Q<B>::type should be float, but GCC believes it's int.
I think this is due to GCC implementing the (non-standard at this time) rule in
CWG1286. This is also reflected in incorrect manglings:
void f(Q<B>) {}
... is mangled as if it were written as `f(Q<A>)`, and other rejects-valids,
such as for:
void f(Q<A>) {}
void f(Q<B>) {}
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug c++/96719] non-standard handling of alias templates used as template template arguments
2020-08-20 1:16 [Bug c++/96719] New: non-standard handling of alias templates used as template template arguments richard-gccbugzilla at metafoo dot co.uk
@ 2020-08-20 7:49 ` redi at gcc dot gnu.org
0 siblings, 0 replies; 2+ messages in thread
From: redi at gcc dot gnu.org @ 2020-08-20 7:49 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96719
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |ABI
Ever confirmed|0 |1
CC| |jason at gcc dot gnu.org
Status|UNCONFIRMED |NEW
Last reconfirmed| |2020-08-20
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Yes I think this was an intentional decision. Possibly also related to CWG
1430.
^ permalink raw reply [flat|nested] 2+ messages in thread
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2020-08-20 1:16 [Bug c++/96719] New: non-standard handling of alias templates used as template template arguments richard-gccbugzilla at metafoo dot co.uk
2020-08-20 7:49 ` [Bug c++/96719] " redi at gcc dot gnu.org
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