print=check-cfg

The tracking issue for this feature is: #125704.


This option of the --print flag print the list of all the expected cfgs.

This is related to the --check-cfg flag which allows specifying arbitrary expected names and values.

This print option works similarly to --print=cfg (modulo check-cfg specifics).

--check-cfg--print=check-cfg
cfg(foo)foo
cfg(foo, values("bar"))foo="bar"
cfg(foo, values(none(), "bar"))foo & foo="bar"
check-cfg specific syntax
cfg(foo, values(any())foo=any()
cfg(foo, values())foo=
cfg(any())any()
noneany()=any()

To be used like this:

rustc --print=check-cfg -Zunstable-options lib.rs