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Date: Fri, 16 Oct 2009 10:38:00 -0000
Message-ID: <84fc9c000910160326t3c5d1650p3ffd02b1c95b2101@mail.gmail.com>
Subject: Re: [Patch] Fix bogus 'function does return' warning
From: Richard Guenther <richard.guenther@gmail.com>
To: Eric Botcazou <ebotcazou@adacore.com>
Cc: gcc-patches@gcc.gnu.org
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On Fri, Oct 16, 2009 at 11:55 AM, Eric Botcazou <ebotcazou@adacore.com> wro=
te:
>> Huh. =A0I wonder why the unreachable blocks are not removed
>> after CFG build? =A0After all noreturn calls end BBs.
>
> It's -O0 so the compiler doesn't see that <L17> is unreachable:
>
> <L17>:
> =A0return;
>
> <L19>:
> =A0finally_tmp.10 =3D 1;
> =A0p.error (); [static-chain: &FRAME.8]
> =A0switch (finally_tmp.10) <default: <L17>, case 1: <L20>>

Ok, so we get lucky at -O1 because decide_copy_try_finally
decides to copy the finally region.  Thus the real reason for
the warning is the return in

        if ((integer) R6b =3D=3D (integer) R5b &&
VIEW_CONVERT_EXPR<character[1:1]>(*R3b.P_ARRAY) =3D=3D "$")
          {
            .gnat_rcheck_20 ("noreturn1.adb", 9);
          }
        else
          {
            .gnat_rcheck_04 ("noreturn1.adb", 11);
          }
        return;

or that .gnat_rcheck_* can appearantly throw (or instead that
EH lowering adds EH edges to the finally block even though
that the functions cannot return).

So, can they throw or is EH lowering at fault here?

Richard.