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Date: Tue, 23 Mar 2021 16:41:26 -0400
From: Mike Frysinger <vapier@gentoo.org>
To: Peng Yu <pengyu.ut@gmail.com>
Cc: libc-help <libc-help@sourceware.org>
Subject: Re: Does glibc has complete test coverage?
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On 23 Mar 2021 11:39, Peng Yu via Libc-help wrote:
> https://www.kernel.org/doc/man-pages/missing_pages.html
> 
> "... quite a few kernel and glibc bugs have been uncovered while
> writing test programs during the preparation of man pages. "
> 
> I see the above text. It doesn't make too much sense, as it indicates
> that glibc does not have complete test coverage.
> 
> Why not taking an approach of always accompanying each line of source
> code with appopriate test cases? If this approach is taken, then most
> bugs should have been eliminated beforehand?

ignoring the legacy aspect (code that's in the tree now but lacks tests),
you have diminishing returns when it comes to writing unittests, and, as
can be seen in a recent discussion, glibc is pretty tightly coupled to
the runtime environment (i.e. the host kernel).  so getting an env that
matches all the different code paths is challenging.

plus it comes down a bit to this being an open source project for many
of us, not a job, and you have to be respectful of balancing quality
and developer time with any requests you make on other volunteers.

along those lines, this is an open source project where "patches are
welcome", so if you wanted to spend your time improving the frameworks
and coverage of our tests, we'd welcome you.

also try googling for "100% test coverage" and reading the variety of
opinions the wider world has on the topic.
-mike