Bug#831185: rumor: FTBFS with GCC 6: notator.cc:337:43: error: call of overloaded 'abs(unsigned int)' is ambiguous

[Lucas Nussbaum]

Source: rumor
Version: 1.0.5-2
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++ -DLOCALEDIR=\"/usr/share/locale\" -DHAVE_CONFIG_H -I. -I..   -Wdate-time -D_FORTIFY_SOURCE=2  -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -D_REENTRANT -pthread -I/usr/include/guile/2.0 -ggdb3 -O0 -Wall -pedantic -c -o notator.o notator.cc
> notator.cc: In member function 'std::__cxx11::string Notator::PitchName(int, bool)':
> notator.cc:337:43: error: call of overloaded 'abs(unsigned int)' is ambiguous
>        NumTics=(abs(RefPitch_wt-AbsPitch_wt)+3)/7;
>                                            ^
> In file included from /usr/include/c++/6/cstdlib:75:0,
>                  from /usr/include/c++/6/ext/string_conversions.h:41,
>                  from /usr/include/c++/6/bits/basic_string.h:5402,
>                  from /usr/include/c++/6/string:52,
>                  from /usr/include/c++/6/bits/locale_classes.h:40,
>                  from /usr/include/c++/6/bits/ios_base.h:41,
>                  from /usr/include/c++/6/ios:42,
>                  from /usr/include/c++/6/ostream:38,
>                  from /usr/include/c++/6/iostream:39,
>                  from rumor.hh:14,
>                  from notator.cc:8:
> /usr/include/stdlib.h:774:12: note: candidate: int abs(int)
>  extern int abs (int __x) __THROW __attribute__ ((__const__)) __wur;
>             ^~~
> In file included from /usr/include/c++/6/ext/string_conversions.h:41:0,
>                  from /usr/include/c++/6/bits/basic_string.h:5402,
>                  from /usr/include/c++/6/string:52,
>                  from /usr/include/c++/6/bits/locale_classes.h:40,
>                  from /usr/include/c++/6/bits/ios_base.h:41,
>                  from /usr/include/c++/6/ios:42,
>                  from /usr/include/c++/6/ostream:38,
>                  from /usr/include/c++/6/iostream:39,
>                  from rumor.hh:14,
>                  from notator.cc:8:
> /usr/include/c++/6/cstdlib:185:3: note: candidate: __int128 std::abs(__int128)
>    abs(__GLIBCXX_TYPE_INT_N_0 __x) { return __x >= 0 ? __x : -__x; }
>    ^~~
> /usr/include/c++/6/cstdlib:180:3: note: candidate: long long int std::abs(long long int)
>    abs(long long __x) { return __builtin_llabs (__x); }
>    ^~~
> /usr/include/c++/6/cstdlib:172:3: note: candidate: long int std::abs(long int)
>    abs(long __i) { return __builtin_labs(__i); }
>    ^~~
> make[4]: *** [notator.o] Error 1

The full build log is available from:
   http://people.debian.org/~lucas/logs/2016/07/13/rumor_1.0.5-2_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.