Re: [Boost-bugs] [Boost C++ Libraries] #13191: undefined reference error when ODR-using boost::ratio::{num, den} (was: undefined symbol)

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #13191: undefined reference error when ODR-using boost::ratio::{num, den} (was: undefined symbol)
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2017-09-05 09:12:13

#13191: undefined reference error when ODR-using boost::ratio::{num,den}
-------------------------------+---------------------
  Reporter:  anonymous         |      Owner:  viboes
      Type:  Bugs              |     Status:  new
 Milestone:  To Be Determined  |  Component:  ratio
   Version:  Boost 1.59.0      |   Severity:  Problem
Resolution:                    |   Keywords:
-------------------------------+---------------------
Changes (by barthelemy@…):

 * version:  Boost 1.63.0 => Boost 1.59.0

Comment:

 if the compiler supports constexpr, the boost::ratio::num or
 boost::ratio::den are declared and initialized, but not defined (see the
 ifdef at line 122 in ratio.hpp). As a consequence, ODR-using num or den
 will result in an unresolved reference.

 Using the attached repro with a compiler which does support constexpr
 gives me:

 {{{
 $ cd ratiosymbol
 $ make
 /usr/lib/ccache/g++ -std=c++11 -c -g -fPIC
 -I/home/sbarthelemy/.local/share/qi/toolchains/linux64/boost/include -o
 test.o test.cc
 /usr/lib/ccache/g++ -std=c++11 -o test test.o
 test.o: In function `main':
 /home/sbarthelemy/ar/s/ratiosymbol/test.cc:9: undefined reference to
 `boost::ratio<1l, 1000000000l>::den'
 /home/sbarthelemy/ar/s/ratiosymbol/test.cc:9: undefined reference to
 `boost::ratio<1l, 1000000000l>::num'
 collect2: error: ld returned 1 exit status
 make: *** [test] Error 1
 $ nm test.o |grep ratio | c++filt
                  U boost::ratio<1l, 1000000000l>::den
                  U boost::ratio<1l, 1000000000l>::num
 $ ${CXX} -v
 Using built-in specs.
 COLLECT_GCC=/usr/bin/g++
 COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.8/lto-wrapper
 Target: x86_64-linux-gnu
 Configured with: ../src/configure -v --with-pkgversion='Ubuntu
 4.8.4-2ubuntu1~14.04.3' --with-
 bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs --enable-
 languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-
 suffix=-4.8 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib
 --without-included-gettext --enable-threads=posix --with-gxx-include-
 dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls --with-sysroot=/
 --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes
 --enable-gnu-unique-object --disable-libmudflap --enable-plugin --with-
 system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-
 cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64/jre --enable-
 java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64
 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-amd64 --with-
 arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
 --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686
 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --with-tune=generic
 --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
 --target=x86_64-linux-gnu
 Thread model: posix
 gcc version 4.8.4 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
 }}}

 I think the proper fix is to remove the #ifdev and thus define num and den
 whether the compiler supports constexpr or not.

-- 
Ticket URL: <https://svn.boost.org/trac10/boost/ticket/13191#comment:1>
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