Re: bugs in dirname module

[Paul Eggert]

Eric Blake <address@hidden> writes:

> OK, how about this approach: continue with the current rule that base_name
> always returns a pointer into the original string without modification.
> On systems where drive prefixes exist, have base_name("a:") return "" (it
> is a root), but base_name("foo/a:b") return "a:b".  Then provide a second
> function, abase_name, which malloc()s the memory for storing the last
> component.  Normally it will just strdup() the base_name of the original
> string, but it does the right thing where base_name is empty (a root, so
> abase_name("a:") gives "a:" instead of "") or where base_name results in a
> drive letter (a multi-component path, so abase_name("foo/a:b") results in
> "./a:b").

I'm trying to map this to the bigger picture, and coming up empty.
Among other things, I don't like having "" be a special case.

How about the following idea instead?  Let's omit abase_name and just
have base_name.  Then we use this rule:

  If you have a valid file name F, then accessing F is the same as
  chdir(dir_name(F)) followed by accessing base_name(F).  Furthermore
  if you successfully { chdir(dir_name(F)); rename(base_name(F),"foo"); },
  you have renamed F to a file named "foo" in the same directory that F was in.

If we go this route, then base_name(F) cannot in general yield a
suffix of F even on Unix systems, since we would want dir_name("a/b/")
== "a/b" and base_name("a/b/") == ".".  Hence base_name will need to
allocate memory in general, even on Unix.  On Cygwin it will need it
to compute "./a:b".

Also, src/dirname.c and src/basename.c will have to be modified to
strip redundant trailing slashes before invoking dir_name and
base_name.