The command:
$ gzip -c foo | gzip -l -
produces the following output consistently:
         compressed        uncompressed  ratio uncompressed_name
                 -1                  -1   0.0% stdout

This is not the expected output, as demonstrated by:
$ gzip -c foo > foo.gz
$ gzip -l - < foo.gz
         compressed        uncompressed  ratio uncompressed_name
               2023                5006  60.2% stdout
$ cat foo.gz | gzip -l -
         compressed        uncompressed  ratio uncompressed_name
                 -1                  -1   0.0% stdout

It's clear that this bug only affects piped input into gzip -l. Why piped input
should be handled differently to stdin input is beyond me.