[Bug c++/67795] Wrong code generated for conditional expression with cast

["frankhb1989 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67795

--- Comment #3 from frankhb1989 at gmail dot com ---
(In reply to Markus Trippelsdorf from comment #1)
> gcc even warns:
> 
> t.cpp: In function ‘std::experimental::fundamentals_v1::string_view&
> erase_left(size_t, std::experimental::fundamentals_v1::string_view&)’:
> t.cpp:9:73: warning: function returns address of local variable
> [-Wreturn-local-addr]
>    return static_cast<string_view &>(n != 0 ? (s.remove_prefix(n), s) : s);
>                                                                          ^

And if the diagnostics exist, they are definitely wrong.

First, here 's' is a local variable (in sense of C++ terms) indeed, but this is
perfectly valid. Note it is a _parameter_ referencing to an object whose
lifetime is unknown in the function/block scopes. This should not trigger such
warnings. Otherwise the identity functions for pointers/references are always
invalid. That's absurd.

Second, the "local variable" wording is somewhat misleading. Returning
reference to a local variable is generally wrong because the variable is an
_automatic object_ and it would be no sense to use the return value to
reference an end-of-life object which would cause undefined behavior.

Anyway, this is just not the case here.
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From: "trippels at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/67795] Wrong code generated for conditional expression with cast
Date: Thu, 01 Oct 2015 12:48:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idg795

Markus Trippelsdorf <trippels at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #4 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Return by value if you want to avoid undefined behavior.