[Debian-med-packaging] Bug#831193: dnaclust: FTBFS with GCC 6: dnaclust.cpp:1772:89: error: call of overloaded 'log(Nucleotides)' is ambiguous

[Lucas Nussbaum]

Source: dnaclust
Version: 3-3
Severity: serious
Tags: stretch sid
User: debian-qa at lists.debian.org
Usertags: qa-ftbfs-20160713 qa-ftbfs
Justification: FTBFS with GCC 6 on amd64

Hi,

During a rebuild of all packages in sid using the gcc-defaults package
available in experimental to make GCC default to version 6, your package failed
to build on amd64. For more information about GCC 6 and Stretch, see:
- https://wiki.debian.org/GCC6
- https://lists.debian.org/debian-devel-announce/2016/06/msg00007.html

Relevant part (hopefully):
> g++  -c -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -Wall -pedantic -std=c++98 -O2  dnaclust.cpp
> dnaclust.cpp: In function 'void makeCluster()':
> dnaclust.cpp:1337:12: warning: variable 'num_threads_to_use' set but not used [-Wunused-but-set-variable]
>      size_t num_threads_to_use = num_threads;
>             ^~~~~~~~~~~~~~~~~~
> dnaclust.cpp:1443:11: warning: variable 'num_threads_to_use' set but not used [-Wunused-but-set-variable]
>        int num_threads_to_use = num_threads;
>            ^~~~~~~~~~~~~~~~~~
> dnaclust.cpp: In function 'int main(int, char**)':
> dnaclust.cpp:1772:89: error: call of overloaded 'log(Nucleotides)' is ambiguous
>        k_mer_length = static_cast<int>(floor(log(median_size) / log(NUMBER_OF_NUCLEOTIDES)));
>                                                                                          ^
> In file included from /usr/include/features.h:364:0,
>                  from /usr/include/x86_64-linux-gnu/c++/6/bits/os_defines.h:39,
>                  from /usr/include/x86_64-linux-gnu/c++/6/bits/c++config.h:495,
>                  from /usr/include/c++/6/iosfwd:38,
>                  from /usr/include/c++/6/ios:38,
>                  from /usr/include/c++/6/istream:38,
>                  from /usr/include/c++/6/sstream:38,
>                  from dnaclust.cpp:1:
> /usr/include/x86_64-linux-gnu/bits/mathcalls.h:109:1: note: candidate: double log(double)
>  __MATHCALL_VEC (log,, (_Mdouble_ __x));
>  ^
> In file included from dnaclust.cpp:3:0:
> /usr/include/c++/6/cmath:365:3: note: candidate: long double std::log(long double)
>    log(long double __x)
>    ^~~
> /usr/include/c++/6/cmath:361:3: note: candidate: float std::log(float)
>    log(float __x)
>    ^~~
> make[1]: *** [dnaclust.o] Error 1

The full build log is available from:
   http://people.debian.org/~lucas/logs/2016/07/13/dnaclust_3-3_unstable_gcc6.log

A list of current common problems and possible solutions is available at
http://wiki.debian.org/qa.debian.org/FTBFS . You're welcome to contribute!

About the archive rebuild: The rebuild was done on EC2 VM instances from
Amazon Web Services, using a clean, minimal and up-to-date chroot. Every
failed build was retried once to eliminate random failures.