[Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules

[Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |paolo.carlini at oracle dot com

--- Comment #2 from Jason Merrill <jason at gcc dot gnu.org> ---
This changed with Paolo's r213776.  These examples suggest that the change to
constant handling WRT -Wnarrowing was a mistake.

[Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Ok, thus what shall we do? Shall we go back to my minimal patch which only
touched enums? https://gcc.gnu.org/ml/gcc-patches/2014-08/msg00880.html

[Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mpolacek at gcc dot gnu.org

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Couldn't you simply turn the error_at into pedwarn?

[Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

--- Comment #6 from Jason Merrill <jason at gcc dot gnu.org> ---
(In reply to Paolo Carlini from comment #5)
> Well, at the time I think we agreed that we wanted to be strict at least
> about enums... Otherwise, yes, we can do that plus setting ok = true in that
> case too, thus collapsing the last two ifs (+ reverting the docs change and
> adjusting the testsuite).

I think that for constants, we want it to be an error without -Wno-narrowing. 
I wonder if the best way to get that is to set pedantic_errors around the
pedwarn call?

[Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

--- Comment #7 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Yes, I was thinking that in such cases clang does something we don't normally
do (ie, an hard error by default suppressible with a -Wno-*). Let me see if we
can achieve that as you suggested.

[Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

--- Comment #8 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Jason, as far as I can see *nowhere* else in the compiler we fiddle with
flag_pedantic_errors, all the tweaks I tried look super hackish to me :( If we
are Ok with just going back to pedwarns the attached passes testing...

[Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

--- Comment #9 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Created attachment 35367
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35367&action=edit
Draft patch

[Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

--- Comment #11 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Created attachment 35370
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35370&action=edit
Draft patch 2

[Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

--- Comment #12 from Jason Merrill <jason at gcc dot gnu.org> ---
(In reply to Paolo Carlini from comment #11)
> Draft patch 2

I think let's go with this.  It's odd, but not complex and does what we want.

[Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #13 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Ok, I'll commit it in an hour or so to trunk. Is it too late for 5.1?

[Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

--- Comment #14 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Paolo Carlini from comment #13)
> Ok, I'll commit it in an hour or so to trunk. Is it too late for 5.1?

It is IMHO too late for that, but not too late for 5.2.

[Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules

[paolo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

--- Comment #15 from paolo at gcc dot gnu.org <paolo at gcc dot gnu.org> ---
Author: paolo
Date: Mon Apr 20 21:46:59 2015
New Revision: 222249

URL: https://gcc.gnu.org/viewcvs?rev=222249&root=gcc&view=rev
Log:
/cp
2015-04-20  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/65801
    * typeck2.c (check_narrowing): In C++11 mode too, -Wno-narrowing
    suppresses the diagnostic.

2015-04-20  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/65801
    * doc/invoke.texi ([-Wnarrowing]): Update.

/testsuite
2015-04-20  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/65801
    * g++.dg/cpp0x/Wnarrowing2.C: New.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/Wnarrowing2.C
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/typeck2.c
    trunk/gcc/doc/invoke.texi
    trunk/gcc/testsuite/ChangeLog

[Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

--- Comment #17 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
(In reply to Manuel López-Ibáñez from comment #16)
> What is printed with -Wno-error=narrowing ?

Try it yourself?
Just a warning.
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

--- Comment #18 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Manuel López-Ibáñez from comment #16)
> What is printed with -Wno-error=narrowing ?

I'm also a bit afraid of how setting pedantic-errors in this way interacts with
the #pragma GCC diagnostics. Wouldn't it be better to reclassify -Wnarrowing as
an error (see diagnostic_classify_diagnostic) then simulate a #pragma GCC
diagnostics pop to restore the previous state? The problem is the order in
which the re-classification happens, which should appear as if it happened in
the command-line and not at the point of warning, but
diagnostic_classify_diagnostic assumes #pragmas are handled in the order given
in the source code.

Another alternative, perhaps simpler, would be to have a different option
-Wnarrowing-strict, which by default is -Werror=narrowing-strict (see
Werror-implicit-function-declaration) and it is enabled by -Wnarrowing. This
way, everything should work as expected (unless latent bugs in the options
handling machinery for not passing the error/warning state correctly when
enabling dependant options).

An even simpler options is to put this under -fpermissive so people realize
that what they are doing is very wrong according to the standard (if it is not
very wrong, then why error and not just pedwarn?).
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

--- Comment #19 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Markus Trippelsdorf from comment #17)
> (In reply to Manuel López-Ibáñez from comment #16)
> > What is printed with -Wno-error=narrowing ?
> 
> Try it yourself?
> Just a warning.

Thanks, well at least that works. I guess if someone notices a problem with the
#pragmas, a better solution can be found later.
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ide801

--- Comment #20 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The problem with -fpermissive is that it doesn't just allow things like
narrowing that are valid in C++03 but also allows all kind of ancient
constructs that no sane person wants.

[Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |5.2

--- Comment #22 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Fixed for 5.2 too.

[Bug c++/65801] [5/6 Regression] Allow -Wno-narrowing to silence stricter C++11 narrowing rules

[evangelos at foutrelis dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65801

Evangelos Foutras <evangelos at foutrelis dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |evangelos at foutrelis dot com

--- Comment #23 from Evangelos Foutras <evangelos at foutrelis dot com> ---
Please note that narrowing conversions don't seem to work the same way they did
in GCC 4.9; I've filed PR c++/66007 for this change in behavior.