This tiny code snippet imports fmtlib, and asks it to format a variant which is valueless by exception. Both the upstream version and the proposed changes will be pulled down by cmake for easy building.

Building with upstream fmtlib is as simple as:

cmake -S . -B upstream
cd upstream
make

Building with the proposed fmtlib change requires only one cmake option

cmake -S . -B fork -DUSE_MY_FORK=YES
cd fork
make