[Bug c++/56868] Constexpr example in 7.1.5/5 fails to compile correctly

["daniel.kruegler at googlemail dot com" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56868

Daniel Krügler <daniel.kruegler at googlemail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |daniel.kruegler at
                   |                            |googlemail dot com

--- Comment #6 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2013-04-07 21:32:46 UTC ---
IMO this behaviour should be considered in the light of

http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#903

Assuming the P/R of this issue becomes accepted, both

static_assert(g2(0) == 1, "g2 failed");
static_assert(g3(0) == 1, "g3 failed");

should fail.
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From: "js-gcc at webkeks dot org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug objc/56870] New: @catch handler broken with SEH
Date: Sun, 07 Apr 2013 21:55:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idV870

             Bug #: 56870
           Summary: @catch handler broken with SEH
    Classification: Unclassified
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: blocker
          Priority: P3
         Component: objc
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: js-gcc@webkeks.org


When trying to use ObjC exceptions with the new SEH support, the caught object
is not the ObjC object, but the _Unwind_Exception instead. Example:

@try {
    id e = [Object new];
    printf("@throw %p\n", e);
    @throw e;
} @catch (id e) {
    printf("@catch %p\n", e);
    @throw e;
}

Expected behaviour: Both are the same pointer.
Observed behaviour: They differ.

Looking further into it, the second pointer is the pointer to the
_Unwind_Exception (I added debug code in objc_exception_throw that outputs the
pointer after the malloc. It is always the same that's received in the catch).

So it seems the generated landing pad for ObjC code is wrong when using SEH. I
think it is correct that the landing pad receives the _Unwind_Exception and not
the ObjC object. But the landing pad needs to get the ObjC exception out of the
_Unwind_Exception and give that back to the user instead of the
_Unwind_Exception, which the user should never see.

This seems to happen not only with 4.8, but also with 4.9.

I marked this bug as blocker, as 4.8 made SEH the default, effectively breaking
ObjC execptions on Windows.