signedness fix

9 jobs for cmake-overhaul-3 in 3 minutes and 55 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #81383
VS2015
VS2015-32-bit

00:01:18

passed #81382
VS2015
VS2015-64-bit

00:01:32

passed #81381
VS2017
VS2017-32-bit

00:01:26

passed #81380
VS2015
VS2017-64-bit

00:01:42

passed #81377
Linux
clang-c++11

00:03:55

passed #81379
Linux
cppcheck

00:02:47

passed #81384
Linux
doc

00:00:23

passed #81376
Linux
gcc-c++11

00:03:30

passed #81378
Apple
macos-c++11

00:02:34