clang + boost regex + xenial = linker error

[nils mccarthy]

I get a linker error compiling the following with clang++-3.8 optimization level -O1:

#include <boost/regex.hpp>

int main() {
  boost::regex re;
  std::string str;
  boost::smatch match;
  boost::regex_match(str, match, re);

  return 0;
}

It works fine with gcc:

$ g++ -O1 -o boost-clang-bug.gcc boost-clang-bug.cpp -lboost_regex

Or with clang -O0:

$ clang++-3.8 -O0 -o boost-clang-bug.o0 boost-clang-bug.cpp -lboost_regex

But not with clang -O1:

$ clang++-3.8 -O1 -o boost-clang-bug.o1 boost-clang-bug.cpp -lboost_regex
/tmp/boost-clang-bug-64dd61.o: In function `boost::cpp_regex_traits<char>::transform[abi:cxx11](char const*, char const*) const':
boost-clang-bug.cpp:(.text._ZNK5boost16cpp_regex_traitsIcE9transformB5cxx11EPKcS3_[_ZNK5boost16cpp_regex_traitsIcE9transformB5cxx11EPKcS3_]+0x23): undefined reference to `boost::re_detail::cpp_regex_traits_implementation<char>::transform[abi:cxx11](char const*, char const*) const'
/tmp/boost-clang-bug-64dd61.o: In function `boost::cpp_regex_traits<char>::transform_primary[abi:cxx11](char const*, char const*) const':
boost-clang-bug.cpp:(.text._ZNK5boost16cpp_regex_traitsIcE17transform_primaryB5cxx11EPKcS3_[_ZNK5boost16cpp_regex_traitsIcE17transform_primaryB5cxx11EPKcS3_]+0x23): undefined reference to `boost::re_detail::cpp_regex_traits_implementation<char>::transform_primary[abi:cxx11](char const*, char const*) const'
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Instead of giving an error, I would expect clang to successfully compile and link this program.

I'm using a stock install of xenial (on AWS, ubuntu/images/hvm-ssd/ubuntu-xenial-16.04-amd64-server-20170113 (ami-7c803d1c)) updating and installing these:

$ sudo apt-get update
$ sudo apt-get install clang-3.8 libboost-regex1.58 g++

Here's relevant versioning information:

$ lsb_release -rd
Description: Ubuntu 16.04.1 LTS
Release: 16.04
$ apt-cache policy clang-3.8
clang-3.8:
  Installed: 1:3.8-2ubuntu4
  Candidate: 1:3.8-2ubuntu4
  Version table:
 *** 1:3.8-2ubuntu4 500
        500 http://us-west-2.ec2.archive.ubuntu.com/ubuntu xenial-updates/universe amd64 Packages
        100 /var/lib/dpkg/status
     1:3.8-2ubuntu1 500
        500 http://us-west-2.ec2.archive.ubuntu.com/ubuntu xenial/universe amd64 Packages

[Launchpad Janitor (janitor)]

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

[Henning Meyer (henning.meyer)]

I get the same error when compiling on 16.04, it links fine on 16.10

I suspect that might be because gcc6 of 16.10 defaults to C++14 when the boost regex libraries were built, but have not verified that

[Henning Meyer (henning.meyer)]

I believe this is a related bug report in debian
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=823978