[Bug c/66322] Linus Torvalds: -Wswitch-bool produces dubious warnings, fails to notice really bad things

["manu at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66322

--- Comment #6 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #2)
> Well, using switch on bool is always weird, one really should use if for
> that.
> If you want fallthrough, then just use if (cond) { first } second, if without
> fallthrough, then if (cond) { first } else { second }.

Indeed. I wrote:

https://gcc.gnu.org/wiki/VerboseDiagnostics#warning:_switch_condition_has_boolean_value_.5B-Wswitch-bool.5D

for future reference. I think there will be always "valid" cases that GCC
cannot avoid warning, so perhaps it is useful to explain the reasoning behind
it and what is the best way to work-around it. (It seems the cast is after all
not the best way, converting it to if-else seems better).
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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/65352] array<T,0>::begin()/end() etc. forms a null reference and breaks on clang+ubsan
Date: Thu, 28 May 2015 11:54:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ide352

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Thu May 28 11:53:35 2015
New Revision: 223806

URL: https://gcc.gnu.org/viewcvs?rev"3806&root=gcc&view=rev
Log:
        PR libstdc++/65352
        * include/std/array (__array_traits::_S_ptr): New function.
        (array::data): Use _S_ptr to avoid creating invalid reference.
        * testsuite/23_containers/array/tuple_interface/get_neg.cc: Adjust
        dg-error line numbers.
        * testsuite/23_containers/array/tuple_interface/tuple_element_neg.cc:
        likewise.

Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/include/std/array
    trunk/libstdc++-v3/testsuite/23_containers/array/tuple_interface/get_neg.cc

trunk/libstdc++-v3/testsuite/23_containers/array/tuple_interface/tuple_element_neg.cc