Bug 1288577 - libstdc++: backport fix for missing "cxx11" abi_tag in special modes
libstdc++: backport fix for missing "cxx11" abi_tag in special modes
Product: Fedora
Classification: Fedora
Component: gcc (Show other bugs)
Unspecified Unspecified
unspecified Severity unspecified
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Assigned To: Jakub Jelinek
Fedora Extras Quality Assurance
Depends On:
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Reported: 2015-12-04 11:09 EST by Stephan Bergmann
Modified: 2016-12-20 11:37 EST (History)
6 users (show)

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Last Closed: 2016-12-20 11:37:49 EST
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Description Stephan Bergmann 2015-12-04 11:09:30 EST
The one-line patch <https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=226022> "Fix abi_tag in special modes" is only present in upstream master, not in F23 libstdc++-devel-5.1.1-4.fc23.x86_64.

With a fix for bug 1282645 forthcoming, it would be great if that patch could be backported to F23 libstdc++, so that Clang does not error out on the empty abi_tag attribute.
Comment 1 Jakub Jelinek 2015-12-04 11:30:44 EST
Jonathan/Jason, was it intentional that it only went into trunk and not into gcc-5-branch?  I'll probably do another set of rpms Monday or so, as GCC 5.3 has been released, wondering if it first should go upstream, or should go to 5.3-RH only, or too risky for backporting.
Comment 2 Jason Merrill 2015-12-04 12:08:43 EST
I imagine I thought it wasn't important to go into 5, but I'll check it in there now.
Comment 3 Jonathan Wakely 2015-12-04 12:12:29 EST
I think that could be backported to gcc-5-branch, otherwise this file generates different symbols on trunk and the branch:

#include <list>
auto f() { return &std::list<int>::size; }

It's hard to come up with a case where it really matters though, because Debug Mode is not ABI compatible, and I think you'd have to refer to some non-public implementation detail to see the effect anyway (according to the standard the program above is not required to even compile, for example).

Clang giving an error is just a Clang bug, the argument on the attribute is optional.
Comment 4 Stephan Bergmann 2015-12-06 08:42:03 EST
(In reply to Jonathan Wakely from comment #3)
> Clang giving an error is just a Clang bug, the argument on the attribute is
> optional.

Is it really optional?  See <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68257> "Reject empty abi_tag attribute on inline namespace."  But maybe I misinterpreted what you meant with "That seems like a bug."
Comment 5 Jonathan Wakely 2015-12-07 05:38:40 EST
I'm not sure what I meant now. Either I was just mistaken, or I thought that  __abi_tag__() should be rejected. Using just __abi_tag__ is definitely intended to work (as Jakub commented on the upstream bug).
Comment 6 Fedora End Of Life 2016-11-24 08:58:19 EST
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Comment 7 Fedora End Of Life 2016-12-20 11:37:49 EST
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