src/immediate_interpreter.cc:910:41: error: array subscript is above array bounds on Trusty

[skymoo]

Trying to build in a Ubuntu Trusty chroot on my Acer C720 and I'm getting the following build error:

g++  -std=gnu++11 -fno-exceptions -fno-strict-aliasing -fPIC -Wall -Wclobbered -Wempty-body -Werror -Wignored-qualifiers -Wmissing-field-initializers -Wmissing-format-attribute -Wmissing-noreturn -Wsign-compare -Wtype-limits -D__STDC_FORMAT_MACROS=1 -D_FILE_OFFSET_BITS=64 -DGESTURES_INTERNAL=1 -Iinclude `pkg-config --cflags glib-2.0` -O3 -DVCSID="\"2.0.4\"" --coverage -ftest-coverage -fprofile-arcs  -I/usr/include/jsoncpp -MMD -c -o obj/immediate_interpreter.o src/immediate_interpreter.cc
src/immediate_interpreter.cc: In member function 'int gestures::FingerButtonClick::EvaluateButtonTypeUsingFigureLocation()':
src/immediate_interpreter.cc:910:41: error: array subscript is above array bounds [-Werror=array-bounds]
       float dist_sq = DistSq(*fingers_[i], *fingers_[j]);
                                         ^
cc1plus: all warnings being treated as errors

I can get things building by removing the -Wall option from the Makefile but silencing warnings always worries me. I'm not very familiar with C++ so don't really know where to start debugging this.