From: Stefan Sperling <stsp@stsp.name>
Subject: Re: Got relies on non-POSIX basename(3), dirname(3)
To: Christian Weisgerber <naddy@mips.inka.de>
Cc: gameoftrees@openbsd.org
Date: Fri, 18 Sep 2020 18:39:03 +0200

On Fri, Sep 18, 2020 at 04:42:52PM +0200, Christian Weisgerber wrote:
> As I mentioned on tech@, OpenBSD declares
> 
> char    *basename(const char *);
> char    *dirname(const char *);
> 
> in contradiction to POSIX, which has plain char* arguments and
> explicitly says that these functions may modify the string.  In
> fact, on FreeBSD they do.
> 
> Unfortunately, Got relies on the string not being modified.  I don't
> know in how many places this breaks, nothing shows up in the
> regression tests, but I stumbled over this case:
> 
> freebsd$ got co got.git
> got: realpath: /home/naddy/got: No such file or directory

This is a direct consequence of not caring about portability early on.
I pretty much ignored most of the portability warnings in OpenBSD man pages.

Could you add basename/dirname overrides to the freebsd version which
copy the string internally before use?

Otherwise I don't think we could do much else but go through the basename
and dirname calls one-by-one to determine whether they rely on the string
to remain unmodified. Where a modifiable string is required, an easy fix
would be to run strdup() first, I guess?