Re: exec: Stricter pathopt parsing

[Jilles Tjoelker <jilles@xxxxxxxx>]

On Tue, May 15, 2018 at 04:49:51PM +0800, Herbert Xu wrote:
> This patch changes the parsing of pathopt.  First of all only
> %builtin and %func (with arbitrary suffixes) will be recognised.
> Any other pathopt will be treated as a normal directory.

> Furthermore, pathopt can now be specified before the directory,
> rather than after it.  In fact, a future version may remove support
> for pathopt suffixes.

> This is so that it is less likely that a genuine directory containing
> a % sign is parsed as a pathopt.

Some examples/testcases would make this clearer.

Note that this also affects CDPATH (good) and MAILPATH (breaks its
undocumented feature to replace the "you have mail" text, which seems
unimportant).

> The patch also removes the clearcmdentry optimisation where we
> attempt to only partially flush the table where possible.

That optimisation is not only a waste of code but also not
POSIX-compliant. XCU 2.9.1.1 Command Search and Execution is clear that
the shell is required to forget remembered locations after an assignment
to PATH, and non-normative text with the hash utility remarks that
PATH="$PATH" is an alternative to hash -r that does not need the XSI
option.

-- 
Jilles Tjoelker
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