G4UIcmdWithADoubleAndUnit: loss of numeric precision when setting a default unit

File test.cpp provides a minimalist example illustrating the problem. Both commands are G4UIcmdWithADoubleAndUnit. The first one (/test/setAngle0 defines a default unit as deg. The second (/test/setAngle1) doesn't. When a default unit is set, the numeric precision is truncated.

The example can be compiled and run as following:

source /usr/local/geant4/bin/geant4.sh
make
./test test.macro

Or using the Dockerfile, E.g. as:

docker build --build-arg DOCKER_TAG=10.04.p03 -t niess/geant4 .

It prints the following result:

setAngle0 : 45.1235 deg
setAngle1 : 45.123456789 deg

The problem was tested to occur with Geant4 9.6.p04 and 10.4.p03. It probably occurs for versions in between as well?

Patch

Issuing /control/useDoublePrecision before loading the macro patches this problem. Now it yields:

setAngle0 : 45.123456789000002 deg
setAngle1 : 45.123456789 deg

but the numeric values of the angles are indeed equal.