When I recently needed to use htab_* functions from libiberty's hashtab.h, I found
that they are completely undocumented: the comments in the header aren't enough
to use them, so I had to look at both the implementation and other uses to figure
libiberty has documentation in source libiberty/hashtab.c.
This is not proper documentation: most part of libiberty use comments which
can be extracted and put into the .texi files, while hashtab.c does not.