Man page is empty. The file /usr/share/man/man1/m4.1.gz has size 25 and zcat on it produces no output.
Created attachment 7057 [details] m4.1.gz Here is mine.
Please add a proper Summary. Check that you have perl installed. If so, remerge and see if its fixed. Seems like the problem is it needs perl to generate manpage.
Added perl as DEPEND some time ago.