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* [Bug c++/89062] class template argument deduction failure with parentheses
[not found] <bug-89062-4@http.gcc.gnu.org/bugzilla/>
@ 2020-10-01 7:08 ` lisyarus at gmail dot com
2020-10-01 13:35 ` mpolacek at gcc dot gnu.org
` (6 subsequent siblings)
7 siblings, 0 replies; 8+ messages in thread
From: lisyarus at gmail dot com @ 2020-10-01 7:08 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89062
Nikita Lisitsa <lisyarus at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |lisyarus at gmail dot com
--- Comment #5 from Nikita Lisitsa <lisyarus at gmail dot com> ---
Any updates on this? Can confirm this on all gcc versions from 7.1 to 10.2 (see
https://godbolt.org/z/4qnfea). Interestingly, for a variadic-template
constructor only the first argument triggers the error, i.e.
template <typename T>
struct A
{
A(T) {}
};
template <typename T>
A(T) -> A<T>;
template <typename T>
struct B
{
template <typename ... Args>
B(Args const & ...){}
};
void test()
{
B<int> b1(A{0}, A{0}, A{0}); // error
B<int> b2(A<int>{0}, A{0}, A{0}); // ok
}
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/89062] class template argument deduction failure with parentheses
[not found] <bug-89062-4@http.gcc.gnu.org/bugzilla/>
2020-10-01 7:08 ` [Bug c++/89062] class template argument deduction failure with parentheses lisyarus at gmail dot com
@ 2020-10-01 13:35 ` mpolacek at gcc dot gnu.org
2021-06-09 0:46 ` mpolacek at gcc dot gnu.org
` (5 subsequent siblings)
7 siblings, 0 replies; 8+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2020-10-01 13:35 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89062
Marek Polacek <mpolacek at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |mpolacek at gcc dot gnu.org
--- Comment #6 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Unfortunately, not yet. I've taken a look at this, and I think I know what the
problem is, but haven't written a fix yet.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/89062] class template argument deduction failure with parentheses
[not found] <bug-89062-4@http.gcc.gnu.org/bugzilla/>
2020-10-01 7:08 ` [Bug c++/89062] class template argument deduction failure with parentheses lisyarus at gmail dot com
2020-10-01 13:35 ` mpolacek at gcc dot gnu.org
@ 2021-06-09 0:46 ` mpolacek at gcc dot gnu.org
2021-07-19 12:49 ` mpolacek at gcc dot gnu.org
` (4 subsequent siblings)
7 siblings, 0 replies; 8+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2021-06-09 0:46 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89062
Marek Polacek <mpolacek at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |brycelelbach at gmail dot com
--- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
*** Bug 100979 has been marked as a duplicate of this bug. ***
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/89062] class template argument deduction failure with parentheses
[not found] <bug-89062-4@http.gcc.gnu.org/bugzilla/>
` (2 preceding siblings ...)
2021-06-09 0:46 ` mpolacek at gcc dot gnu.org
@ 2021-07-19 12:49 ` mpolacek at gcc dot gnu.org
2021-08-08 17:10 ` ppalka at gcc dot gnu.org
` (3 subsequent siblings)
7 siblings, 0 replies; 8+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2021-07-19 12:49 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89062
Marek Polacek <mpolacek at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |gareth@ignition-web.co.uk
--- Comment #8 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
*** Bug 101509 has been marked as a duplicate of this bug. ***
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/89062] class template argument deduction failure with parentheses
[not found] <bug-89062-4@http.gcc.gnu.org/bugzilla/>
` (3 preceding siblings ...)
2021-07-19 12:49 ` mpolacek at gcc dot gnu.org
@ 2021-08-08 17:10 ` ppalka at gcc dot gnu.org
2021-08-11 19:59 ` cvs-commit at gcc dot gnu.org
` (2 subsequent siblings)
7 siblings, 0 replies; 8+ messages in thread
From: ppalka at gcc dot gnu.org @ 2021-08-08 17:10 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89062
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |ppalka at gcc dot gnu.org
Assignee|unassigned at gcc dot gnu.org |ppalka at gcc dot gnu.org
Status|NEW |ASSIGNED
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/89062] class template argument deduction failure with parentheses
[not found] <bug-89062-4@http.gcc.gnu.org/bugzilla/>
` (4 preceding siblings ...)
2021-08-08 17:10 ` ppalka at gcc dot gnu.org
@ 2021-08-11 19:59 ` cvs-commit at gcc dot gnu.org
2021-08-11 20:03 ` ppalka at gcc dot gnu.org
2021-10-06 15:18 ` avi@cloudius-systems.com
7 siblings, 0 replies; 8+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2021-08-11 19:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89062
--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:
https://gcc.gnu.org/g:6186708312780bb2139da01946abdde39667e985
commit r12-2859-g6186708312780bb2139da01946abdde39667e985
Author: Patrick Palka <ppalka@redhat.com>
Date: Wed Aug 11 15:58:30 2021 -0400
c++: most vexing parse and braced CTAD [PR89062]
Here grokdeclarator is emitting the error
error: class template placeholder âFooâ not permitted in this context
during the tentative (and ultimately futile) parse of 'x' as a function
declaration. This happens because when parsing 'Foo{1}',
cp_parser_parameter_declaration yields a parameter declaration with no
declarator and whose type is a CTAD placeholder, and stops short of
consuming the '{'. The caller cp_parser_parameter_declaration_list then
calls grokdeclarator on this declarator, hence the error, and soon
thereafter we abort this tentative parse since the next token '{'
doesn't make sense in the context of a parameter list.
Note that we don't have this issue with parenthesized CTAD
Foo<int> x(Foo(1));
because in this case cp_parser_direct_declarator (called indirectly from
c_p_p_d) consumes the '(' and returns cp_error_declarator instead of a
NULL declarator (and also simulates a parse error), and grokdeclarator
exits early for this declarator without emitting any error.
Since grokdeclarator doesn't take a 'complain' parameter, to fix this we
need to avoid calling grokdeclarator in this situation. To that end
this patch makes c_p_p_d simulate an error when a construct is a CTAD
expression and definitely not a parameter declaration, so that c_p_p_d_l
can avoid calling grokdeclarator by checking for this simulated error.
Alternatively we could keep all this logic inside c_p_p_d_l and not
touch c_p_p_d at all, but this approach seems slightly less adhoc.
PR c++/89062
gcc/cp/ChangeLog:
* parser.c (cp_parser_parameter_declaration_list): Don't call
grokdeclarator if cp_parser_error_occurred.
(cp_parser_parameter_declaration): Simulate an error if we see
the beginning of a CTAD form, i.e. if we see an opening brace
after the decl-specifier-seq and the type is a CTAD placeholder.
gcc/testsuite/ChangeLog:
* g++.dg/cpp1z/class-deduction97.C: New test.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/89062] class template argument deduction failure with parentheses
[not found] <bug-89062-4@http.gcc.gnu.org/bugzilla/>
` (5 preceding siblings ...)
2021-08-11 19:59 ` cvs-commit at gcc dot gnu.org
@ 2021-08-11 20:03 ` ppalka at gcc dot gnu.org
2021-10-06 15:18 ` avi@cloudius-systems.com
7 siblings, 0 replies; 8+ messages in thread
From: ppalka at gcc dot gnu.org @ 2021-08-11 20:03 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89062
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |FIXED
Target Milestone|--- |12.0
--- Comment #10 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Fixed for GCC 12.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/89062] class template argument deduction failure with parentheses
[not found] <bug-89062-4@http.gcc.gnu.org/bugzilla/>
` (6 preceding siblings ...)
2021-08-11 20:03 ` ppalka at gcc dot gnu.org
@ 2021-10-06 15:18 ` avi@cloudius-systems.com
7 siblings, 0 replies; 8+ messages in thread
From: avi@cloudius-systems.com @ 2021-10-06 15:18 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89062
Avi Kivity <avi@cloudius-systems.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |avi@cloudius-systems.com
--- Comment #11 from Avi Kivity <avi@cloudius-systems.com> ---
Seeing this in 11.2, so asking for a backport.
^ permalink raw reply [flat|nested] 8+ messages in thread
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[not found] <bug-89062-4@http.gcc.gnu.org/bugzilla/>
2020-10-01 7:08 ` [Bug c++/89062] class template argument deduction failure with parentheses lisyarus at gmail dot com
2020-10-01 13:35 ` mpolacek at gcc dot gnu.org
2021-06-09 0:46 ` mpolacek at gcc dot gnu.org
2021-07-19 12:49 ` mpolacek at gcc dot gnu.org
2021-08-08 17:10 ` ppalka at gcc dot gnu.org
2021-08-11 19:59 ` cvs-commit at gcc dot gnu.org
2021-08-11 20:03 ` ppalka at gcc dot gnu.org
2021-10-06 15:18 ` avi@cloudius-systems.com
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