A
functional GFCI may make it safe.
I point that out as GFCIs have a very high faliure rate. (OR they had, I am not sure how they are doing now)
However it will not make it code compliant.
For what it's worth protecting a Feeder with a GFCI is not a great design.
The cumulative leakage current of all the branch circuits will likely lead to nuisance tripping of the feeder.
And having a feeder nuisance tripping is much more than a nuisance.