need operator-- for mozc::ZeroQueryDict::iterator

[farseerfc]

Otherwise on gcc 8.1 STL library will complain errors like:

In file included from ../../engine/engine.cc:30:
In file included from /build/fcitx5-mozc-git/src/mozc/src/engine/engine.h:33:
In file included from /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.0/../../../../include/c++/8.1.0/memory:62:
In file included from /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.0/../../../../include/c++/8.1.0/bits/stl_algobase.h:66:
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.0/../../../../include/c++/8.1.0/bits/stl_iterator_base_funcs.h:183:2: error: cannot decrement value of type 'mozc::ZeroQueryDict::iterator'
        --__i;
        ^ ~~~
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.0/../../../../include/c++/8.1.0/bits/stl_iterator_base_funcs.h:206:12: note: in instantiation of function template specialization 'std::__advance<mozc::ZeroQueryDict::iterator, long>' requested here
      std::__advance(__i, __d, std::__iterator_category(__i));
           ^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.0/../../../../include/c++/8.1.0/bits/stl_algo.h:2137:9: note: in instantiation of function template specialization 'std::advance<mozc::ZeroQueryDict::iterator, long>' requested here
          std::advance(__middle, __half);
               ^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/8.1.0/../../../../include/c++/8.1.0/bits/stl_algo.h:2190:19: note: in instantiation of function template specialization 'std::__equal_range<mozc::ZeroQueryDict::iterator, unsigned long, __gnu_cxx::__ops::_Iter_less_val, __gnu_cxx::__ops::_Val_less_iter>' requested here
      return std::__equal_range(__first, __last, __val,
                  ^
/build/fcitx5-mozc-git/src/mozc/src/prediction/zero_query_dict.h:213:17: note: in instantiation of function template specialization 'std::equal_range<mozc::ZeroQueryDict::iterator, unsigned long>' requested here
    return std::equal_range(begin(), end(), iter.index());
                ^
1 error generated.

A full error message is here: https://fars.ee/DAiY

I have written a patch to fix this: https://fars.ee/2is4

[musover]

I have been able to reproduce this issue.

[597/747] /usr/bin/x86_64-pc-linux-gnu-g++ -MMD -MF obj/engine/engine.engine.o.d -DOS_LINUX -DMOZC_BUILD -DCHANNEL_DEV -DNDEBUG -DQT_NO_DEBUG -DNO_LOGGING -DIGNORE_HELP_FLAG -DIGNORE_INVALID_FLAG -I/var/tmp/portage/app-i18n/mozc-9999/work/mozc-9999/src -Igen -Igen/proto_
out -Wall -Wno-char-subscripts -Wno-sign-compare -Wno-deprecated-declarations -Wwrite-strings -Wno-unknown-warning-option -Wno-inconsistent-missing-override -fPIC -fno-exceptions -fmessage-length=0 -fno-strict-aliasing -funsigned-char -pipe -pthread -fno-omit-frame-point
er -fstack-protector --param=ssp-buffer-size=4 -Wtype-limits -march=native -O2 -pipe -Wno-deprecated -Wno-covered-switch-default -Wno-unnamed-type-template-args -Wno-c++11-narrowing -std=gnu++0x -std=gnu++0x  -c ../../engine/engine.cc -o obj/engine/engine.engine.o
FAILED: obj/engine/engine.engine.o                                                      
/usr/bin/x86_64-pc-linux-gnu-g++ -MMD -MF obj/engine/engine.engine.o.d -DOS_LINUX -DMOZC_BUILD -DCHANNEL_DEV -DNDEBUG -DQT_NO_DEBUG -DNO_LOGGING -DIGNORE_HELP_FLAG -DIGNORE_INVALID_FLAG -I/var/tmp/portage/app-i18n/mozc-9999/work/mozc-9999/src -Igen -Igen/proto_out -Wall
-Wno-char-subscripts -Wno-sign-compare -Wno-deprecated-declarations -Wwrite-strings -Wno-unknown-warning-option -Wno-inconsistent-missing-override -fPIC -fno-exceptions -fmessage-length=0 -fno-strict-aliasing -funsigned-char -pipe -pthread -fno-omit-frame-pointer -fstack
-protector --param=ssp-buffer-size=4 -Wtype-limits -march=native -O2 -pipe -Wno-deprecated -Wno-covered-switch-default -Wno-unnamed-type-template-args -Wno-c++11-narrowing -std=gnu++0x -std=gnu++0x  -c ../../engine/engine.cc -o obj/engine/engine.engine.o
In file included from /usr/lib/gcc/x86_64-pc-linux-gnu/8.1.0/include/g++-v8/bits/stl_algobase.h:66,
                 from /usr/lib/gcc/x86_64-pc-linux-gnu/8.1.0/include/g++-v8/memory:62,
                 from /var/tmp/portage/app-i18n/mozc-9999/work/mozc-9999/src/engine/engine.h:33,
                 from ../../engine/engine.cc:30:
/usr/lib/gcc/x86_64-pc-linux-gnu/8.1.0/include/g++-v8/bits/stl_iterator_base_funcs.h: In instantiation of ‘void std::__advance(_RandomAccessIterator&, _Distance, std::random_access_iterator_tag) [with _RandomAccessIterator = mozc::ZeroQueryDict::iterator; _Distance = lon
g int]’:
/usr/lib/gcc/x86_64-pc-linux-gnu/8.1.0/include/g++-v8/bits/stl_iterator_base_funcs.h:206:21:   required from ‘void std::advance(_InputIterator&, _Distance) [with _InputIterator = mozc::ZeroQueryDict::iterator; _Distance = long int]’
/usr/lib/gcc/x86_64-pc-linux-gnu/8.1.0/include/g++-v8/bits/stl_algo.h:2137:16:   required from ‘std::pair<_FIter, _FIter> std::__equal_range(_ForwardIterator, _ForwardIterator, const _Tp&, _CompareItTp, _CompareTpIt) [with _ForwardIterator = mozc::ZeroQueryDict::iterator
; _Tp = long unsigned int; _CompareItTp = __gnu_cxx::__ops::_Iter_less_val; _CompareTpIt = __gnu_cxx::__ops::_Val_less_iter]’
/usr/lib/gcc/x86_64-pc-linux-gnu/8.1.0/include/g++-v8/bits/stl_algo.h:2190:32:   required from ‘std::pair<_FIter, _FIter> std::equal_range(_FIter, _FIter, const _Tp&) [with _FIter = mozc::ZeroQueryDict::iterator; _Tp = long unsigned int]’
/var/tmp/portage/app-i18n/mozc-9999/work/mozc-9999/src/prediction/zero_query_dict.h:213:57:   required from here
/usr/lib/gcc/x86_64-pc-linux-gnu/8.1.0/include/g++-v8/bits/stl_iterator_base_funcs.h:183:2: error: no match for ‘operator--’ (operand type is ‘mozc::ZeroQueryDict::iterator’)
  --__i;                                       
  ^~~~~

[miangraham]

This breaks the mozc build for me on current arch linux (-S mozc uim-mozc). @farseerfc's patch confirmed working.

[Arfrever]

The relevant change in GCC libstdc++ which caused this problem for Mozc is:
https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=248875

[Arfrever]

I think that for consistency with other code the new functions should be added at line 150, not 135.

[hiroyuki-komatsu]

a1dcada fixed this issue.

Thank you for the report.