[Toybox] [PATCH] lib: getdirname fix seqfault on null ptr

[Rob Landley]

On 10/19/19 1:59 AM, Jarno Mäkipää wrote:
> In order to be used as drop in replacement for dirname()
> 
> If path is a null pointer or points to an empty string,
> dirname() shall return a pointer to the string "." .

Applied, but it's not a drop-in replacement because it returns a malloc() and
the other either modifies its input string (!) or returns a static ".".

I made getdirname() because A) modifying your input argument is rude, B) I
needed to do getbasename() anyway (which glibc has two versions of that behave
differently, depending on which header you include first) and I wanted a
getdirname() with the same semantics as that.

Unfortunately, I misremembered getbasename()'s semantics, and it's _not_
returning a malloc. It's just returning either strrchr(name, '.')+1 or name if
there's no '/'; So my cp cleannup segfaulted until I moved the free() back under
the if (FLAG(D)) and now I want to fix the semantics to be consistent and I'm
tempted to rip getdirname back _out_ except modifying your argument is still
unfortunate...

(Sorry, I'm getting a bit overwhelmed juggling as many patches and bug reports
as I'm getting. I cut the release, but I still need to track down the tar bug
report, and I think I've dropped at least one of Elliott's xargs patches,
there's trailing ls spaces, people keep doing github comments instead of mailing
list stuff which get dropped on the floor regularly because there's no obvious
replacement for a mailing list archive there...)

Rob