public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug c++/90320] [8/9/10 Regression] Explicit constructor called implicitly
[not found] <bug-90320-4@http.gcc.gnu.org/bugzilla/>
@ 2020-04-23 1:22 ` mpolacek at gcc dot gnu.org
2020-04-23 8:03 ` paolo.carlini at oracle dot com
` (3 subsequent siblings)
4 siblings, 0 replies; 5+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2020-04-23 1:22 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90320
Marek Polacek <mpolacek at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at gcc dot gnu.org |mpolacek at gcc dot gnu.org
Status|NEW |ASSIGNED
CC| |mpolacek at gcc dot gnu.org
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/90320] [8/9/10 Regression] Explicit constructor called implicitly
[not found] <bug-90320-4@http.gcc.gnu.org/bugzilla/>
2020-04-23 1:22 ` [Bug c++/90320] [8/9/10 Regression] Explicit constructor called implicitly mpolacek at gcc dot gnu.org
@ 2020-04-23 8:03 ` paolo.carlini at oracle dot com
2020-04-27 1:09 ` cvs-commit at gcc dot gnu.org
` (2 subsequent siblings)
4 siblings, 0 replies; 5+ messages in thread
From: paolo.carlini at oracle dot com @ 2020-04-23 8:03 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90320
--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Thanks Marek.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/90320] [8/9/10 Regression] Explicit constructor called implicitly
[not found] <bug-90320-4@http.gcc.gnu.org/bugzilla/>
2020-04-23 1:22 ` [Bug c++/90320] [8/9/10 Regression] Explicit constructor called implicitly mpolacek at gcc dot gnu.org
2020-04-23 8:03 ` paolo.carlini at oracle dot com
@ 2020-04-27 1:09 ` cvs-commit at gcc dot gnu.org
2020-04-27 1:11 ` [Bug c++/90320] [8/9 " mpolacek at gcc dot gnu.org
2020-05-13 17:31 ` mpolacek at gcc dot gnu.org
4 siblings, 0 replies; 5+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2020-04-27 1:09 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90320
--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:
https://gcc.gnu.org/g:feb801f62239528bca2cfb6c3abd70d434b69c0a
commit r10-7979-gfeb801f62239528bca2cfb6c3abd70d434b69c0a
Author: Marek Polacek <polacek@redhat.com>
Date: Wed Apr 22 20:12:47 2020 -0400
c++: Explicit constructor called in copy-initialization [PR90320]
This test is rejected with a bogus "use of deleted function" error
starting with r225705 whereby convert_like_real/ck_base no longer
sets LOOKUP_ONLYCONVERTING for user_conv_p conversions. This does
not seem to be always correct. To recap, when we have something like
T t = x where T is a class type and the type of x is not T or derived
from T, we perform copy-initialization, something like:
1. choose a user-defined conversion to convert x to T, the result is
a prvalue,
2. use this prvalue to direct-initialize t.
In the second step, explicit constructors should be considered, since
we're direct-initializing. This is what r225705 fixed.
In this PR we are dealing with the first step, I think, where explicit
constructors should be skipped. [over.match.copy] says "The converting
constructors of T are candidate functions" which clearly eliminates
explicit constructors. But we also have to copy-initialize the argument
we are passing to such a converting constructor, and here we should
disregard explicit constructors too.
In this testcase we have
V v = m;
and we choose V::V(M) to convert m to V. But we wrongly choose
the explicit M::M<M&>(M&) to copy-initialize the argument; it's
a better match for a non-const lvalue than the implicit M::M(const M&)
but because it's explicit, we shouldn't use it.
When convert_like is processing the ck_user conversion -- the convfn is
V::V(M) -- it can see that cand->flags contains LOOKUP_ONLYCONVERTING,
but then when we're in build_over_call for this convfn, we have no way
to pass the flag to convert_like for the argument 'm', because convert_like
doesn't take flags. Fixed by creating a new conversion flag, copy_init_p,
set in ck_base/ck_rvalue to signal that explicit constructors should be
skipped.
LOOKUP_COPY_PARM looks relevant, but again, it's a LOOKUP_* flag, so
can't pass it to convert_like. DR 899 also seemed related, but that
deals with direct-init contexts only.
PR c++/90320
* call.c (struct conversion): Add copy_init_p.
(standard_conversion): Set copy_init_p in ck_base and ck_rvalue
if FLAGS demands LOOKUP_ONLYCONVERTING.
(convert_like_real) <case ck_base>: If copy_init_p is set, or
LOOKUP_ONLYCONVERTING into FLAGS.
* g++.dg/cpp0x/explicit13.C: New test.
* g++.dg/cpp0x/explicit14.C: New test.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/90320] [8/9 Regression] Explicit constructor called implicitly
[not found] <bug-90320-4@http.gcc.gnu.org/bugzilla/>
` (2 preceding siblings ...)
2020-04-27 1:09 ` cvs-commit at gcc dot gnu.org
@ 2020-04-27 1:11 ` mpolacek at gcc dot gnu.org
2020-05-13 17:31 ` mpolacek at gcc dot gnu.org
4 siblings, 0 replies; 5+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2020-04-27 1:11 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90320
Marek Polacek <mpolacek at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|[8/9/10 Regression] |[8/9 Regression] Explicit
|Explicit constructor called |constructor called
|implicitly |implicitly
--- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed on trunk so far. I'm considering backporting the fix to 9 too.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/90320] [8/9 Regression] Explicit constructor called implicitly
[not found] <bug-90320-4@http.gcc.gnu.org/bugzilla/>
` (3 preceding siblings ...)
2020-04-27 1:11 ` [Bug c++/90320] [8/9 " mpolacek at gcc dot gnu.org
@ 2020-05-13 17:31 ` mpolacek at gcc dot gnu.org
4 siblings, 0 replies; 5+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2020-05-13 17:31 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90320
Marek Polacek <mpolacek at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |FIXED
--- Comment #8 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Actually, maybe not. But it's fixed in GCC 10. I can backport if anyone
thinks it's important.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2020-05-13 17:31 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
[not found] <bug-90320-4@http.gcc.gnu.org/bugzilla/>
2020-04-23 1:22 ` [Bug c++/90320] [8/9/10 Regression] Explicit constructor called implicitly mpolacek at gcc dot gnu.org
2020-04-23 8:03 ` paolo.carlini at oracle dot com
2020-04-27 1:09 ` cvs-commit at gcc dot gnu.org
2020-04-27 1:11 ` [Bug c++/90320] [8/9 " mpolacek at gcc dot gnu.org
2020-05-13 17:31 ` mpolacek at gcc dot gnu.org
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).