error: 'basic_string<_CharT, _Traits, _Allocator>' is missing exception specification

[Giuseppe D'Angelo]

This is mirroring Debian bug #808086 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=808086

Compiling any source file that includes <string> with clang 3.8 and -std=c++11 -stdlib=libc++ results in a compile error.

While this is a minor bug in Debian (as it doesn't ship 3.8 yet), xenial does, and that's a major problem as it makes libc++ useless.

clang: warning: argument unused during compilation: '-stdlib=libc++'
In file included from test.cpp:1:
In file included from /usr/include/c++/v1/iostream:38:
In file included from /usr/include/c++/v1/ios:216:
In file included from /usr/include/c++/v1/__locale:15:
/usr/include/c++/v1/string:1938:44: error: 'basic_string<_CharT, _Traits, _Allocator>' is missing exception specification 'noexcept(is_nothrow_copy_constructible<allocator_type>::value)'
basic_string<_CharT, _Traits, _Allocator>::basic_string(const allocator_type& __a)
                                           ^
/usr/include/c++/v1/string:1326:76: note: previous declaration is here
    __attribute__ ((__visibility__("hidden"), __always_inline__)) explicit basic_string(const allocator_type& __a)
                                                                           ^
1 error generated.

--

Update (30 Aug 2017): as per https://wiki.ubuntu.com/StableReleaseUpdates :

[Impact]

This bug makes it impossible to compile any C++11 source file that includes <string> with clang 3.8 using libc++. Any non-trivial C++11 codebase is affected, making the whole libc++ package useless.

[Test Case]

See above. Create a C++ file that simply contains #include <string> and compile it with clang++ -std=c++11 -stdlib=libc++ file.cpp.

[Regression Potential]

The current <string> header simply does not work with clang-3.8 under any condition, so there is no regression potential.

The regression potential for GCC is also extremely limited: no package whatsoever uses GCC in combination with libc++, and the fact that GCC 5.4 -- currently in Xenial -- does not detect the error that Clang detects is just showing that GCC is bugged in this regard.

[Other Info]

The patch/workaround fixes the problem. See also the discussion at the linked Debian bug report as well as https://stackoverflow.com/q/37096062

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Tony Lewis (tonyelewis)]

This problem's still active in 16.10 (Yakkety).

Discussion of this issue on Stack Overflow:

http://stackoverflow.com/q/37096062

One commenter ("peppe") argues this bug is worse on Ubuntu than on Debian because the broken version only ships as experimental in Debian.

Workaround:

http://stackoverflow.com/a/38385967

[VestniK (vestnik)]

I've added patch to solve this issue to the list of debian/patches rebuild the package and checked that this issue is fixed. Debdiff file is attached.

[Ubuntu Foundations Team Bug Bot (crichton)]

The attachment "proposed patch to the deb package in xenial" seems to be a debdiff. The ubuntu-sponsors team has been subscribed to the bug report so that they can review and hopefully sponsor the debdiff. If the attachment isn't a patch, please remove the "patch" flag from the attachment, remove the "patch" tag, and if you are member of the ~ubuntu-sponsors, unsubscribe the team.

[This is an automated message performed by a Launchpad user owned by ~brian-murray, for any issue please contact him.]

[Simon Quigley (tsimonq2)]

Hello!

Could you please indicate which releases are still affected by this? Also, if you would like to get this in Xenial, which is a stable release, please follow the SRU policy: https://wiki.ubuntu.com/StableReleaseUpdates

For now, I'm unsubscribing ~ubuntu-sponsors because it's not clear what there is to sponsor. Please feel free to resubscribe ~ubuntu-sponsors once things are clarified.

Thanks!

[Giuseppe D'Angelo (dangelo)]

Hello,

Xenial is still affected by this AFAICS. And yes, I'd like it to be fixed there.

17.04/17.10 shouldn't be affected, as they're using libc++ 3.9.1 which has fixed the corresponding bug in Debian. (No idea about ~ubuntu-sponsors, to be honest...).

[Giuseppe D'Angelo (dangelo)]

Added the SRU info, added ~ubuntu-bug-control.

[Giuseppe D'Angelo (dangelo)]

Could also someone set the severity to High? As per:

"Renders essential features or functionality of the application or dependencies broken or ineffective "

[Simon Quigley (tsimonq2)]

Sponsored to Xenial.

Thank you for your contribution to Ubuntu! It's really appreciated. :)

[Brian Murray (brian-murray)]

Hello Giuseppe, or anyone else affected,

Accepted libc++ into xenial-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/libc++/3.7.0-1ubuntu0.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed.Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested and change the tag from verification-needed-xenial to verification-done-xenial. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-xenial. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

[Giuseppe D'Angelo (dangelo)]

Seems to be working just fine here, thank you very much!

Verification steps:

1. Get a C++11 source file that #includes <string>:

#include <string>

int main() {
    std::string s{"foobar"};
}

2. compile it with clang++ -stdlib=libc++ -std=c++11

3. if it compiles (which now it does) the bug is fixed.

[Launchpad Janitor (janitor)]

This bug was fixed in the package libc++ - 3.7.0-1ubuntu0.1

---------------
libc++ (3.7.0-1ubuntu0.1) xenial; urgency=medium

  * Fix error int the string header in c++11 mode (LP: #1610168).

 -- Sergey Vidyuk <email address hidden> Sat, 24 Jun 2017 18:09:34 +0700

[Brian Murray (brian-murray)]

The verification of the Stable Release Update for libc++ has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.