Mark throw_exception as noreturn?

[Andrey Semashev-2]

Hi,

I was wondering why the throw_exception function is not marked as
noreturn? This makes it troublesome to use it as a drop-in replacement
for throw statements as it starts to flag compiler warnings about
missing return statements in non-void functions.

I suggest to mark the function as noreturn at least for compilers that
support it. GCC has __attribute__((noreturn)), MSVC has
__declspec(noreturn).
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[Gennaro Prota-2]

Andrey Semashev wrote:
> Hi,
>
> I was wondering why the throw_exception function is not marked as
> noreturn?

I don't know. That could be because not all compilers support
that annotation (but then, that's not usually something which
scares Boost off).

> This makes it troublesome to use it as a drop-in replacement
> for throw statements as it starts to flag compiler warnings about
> missing return statements in non-void functions.
>
> I suggest to mark the function as noreturn at least for compilers that
> support it. GCC has __attribute__((noreturn)), MSVC has
> __declspec(noreturn).

I don't know what they guys here want to do, or whether there's
an accepted solution to this. For the immediate needs, however,
you could use BOOST_UNREACHABLE_RETURN in the calling function.

--
Genny

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[Andrey Semashev-2]

Gennaro Prota wrote:

> For the immediate needs, however,
> you could use BOOST_UNREACHABLE_RETURN in the calling function.

>From what I see from Boost.Config headers, the macro unfolds to
something non-empty only for three compilers, and GCC is not among them.
I encountered the problem with GCC.
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[Mathias Gaunard-2]

Andrey Semashev wrote:

> I was wondering why the throw_exception function is not marked as
> noreturn? This makes it troublesome to use it as a drop-in replacement
> for throw statements as it starts to flag compiler warnings about
> missing return statements in non-void functions.
>
> I suggest to mark the function as noreturn at least for compilers that
> support it. GCC has __attribute__((noreturn)), MSVC has
> __declspec(noreturn).

Why is throw_exception detected as returning something in the first place?

I've personally tried to force __attribute__((noreturn)) with GCC, but
it doesn't work, it says the function does return.

Looking at the code though, I can't tell what is wrong with it.
A fix to that would be appreciated. Without that, I'd personally rather
not use throw_exception.

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[Emil Dotchevski-3]

On Sat, Jul 4, 2009 at 6:11 PM, Mathias
Gaunard<mathias.gaunard@...> wrote:

> Andrey Semashev wrote:
>
>> I was wondering why the throw_exception function is not marked as
>> noreturn? This makes it troublesome to use it as a drop-in replacement
>> for throw statements as it starts to flag compiler warnings about
>> missing return statements in non-void functions.
>>
>> I suggest to mark the function as noreturn at least for compilers that
>> support it. GCC has __attribute__((noreturn)), MSVC has
>> __declspec(noreturn).
>
> Why is throw_exception detected as returning something in the first place?
>
> I've personally tried to force __attribute__((noreturn)) with GCC, but it
> doesn't work, it says the function does return.
>
> Looking at the code though, I can't tell what is wrong with it.
> A fix to that would be appreciated. Without that, I'd personally rather not
> use throw_exception.

I've added a macro BOOST_ATTRIBUTE_NORETURN. The problem is fixed for
MSVC, feel free to add support for other compilers in
boost/exception/detail/attribute_noreturn.hpp.

Emil Dotchevski
Reverge Studios, Inc.
http://www.revergestudios.com/reblog/index.php?n=ReCode
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[Andrey Semashev-2]

Emil Dotchevski wrote:

> I've added a macro BOOST_ATTRIBUTE_NORETURN. The problem is fixed for
> MSVC, feel free to add support for other compilers in
> boost/exception/detail/attribute_noreturn.hpp.

Should it really be part of Boost.Exception (moreover, private part)?
Maybe it's better to be in Boost.Config?
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[Emil Dotchevski-3]

On Sun, Jul 5, 2009 at 2:13 AM, Andrey
Semashev<andrey.semashev@...> wrote:
> Emil Dotchevski wrote:
>
>> I've added a macro BOOST_ATTRIBUTE_NORETURN. The problem is fixed for
>> MSVC, feel free to add support for other compilers in
>> boost/exception/detail/attribute_noreturn.hpp.
>
> Should it really be part of Boost.Exception (moreover, private part)? Maybe
> it's better to be in Boost.Config?

Probably the correct place is Boost.Config, but so far
boost::throw_exception (which is part of Boost Exception) seems to be
the only function that needs this macro and I thought we don't have
good enough reason to add weight to Boost.Config at this point. It'll
take no time at all to make BOOST_ATTRIBUTE_NORETURN official if it is
needed elsewhere in the future.

Emil Dotchevski
Reverge Studios, Inc.
http://www.revergestudios.com/reblog/index.php?n=ReCode
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