[bug-gawk] empty AWK*PATH inconsistency

[Andrew J. Schorr]

Hi,

In comp.lang.awk, Kenny McCormack noted an inconsistency in how AWKPATH
and AWKLIBPATH (henceforth called AWK*PATH) are handled.

When you set AWK*PATH="" in the environment, the logic in io.c to find code
decides that it should use the default value, since the value from the
environment is empty.  But when ENVIRON["AWK*PATH"] is created in main.c, it
inserts the default value only when AWK*PATH is entirely missing from the
environment.  In other words, there's some inconsistency about how to handle
the case when AWK*PATH is present in the environment, but equals the empty
string.  This behavior appears to be very old.  The documentation does not
appear to me to explain this behavior.

Basically, there are 3 cases:
   1. AWK*PATH not in environment -> use the default path
   2. AWK*PATH in environment but equal to the empty string -> ?
   3. AWK*PATH set and not empty -> use the environment value

We are currently inconsistent about how we handle case #2.  So the
first task is to decide how it should be handled.  If we want to 
use the default value, then we should update the docs and ENVIRON
setup to reflect that.

There's also a question of whether the current working directory (cwd) should
be searched automatically or not.  At the moment, the cwd is searched
before AWKPATH, but not before AWKLIBPATH.

In private communication, Arnold suggested having this discussion on the
bug list.

On Mon, Oct 06, 2014 at 07:15:55PM +0300, Aharon Robbins wrote:
> AWKPATH was added at 2.10. From the code that I have for that, if
> AWKPATH was empty, it continued to use the default value. I think that was
> more of a "don't assign a null pointer to the path search variable" decision
> than a "use the default if AWKLIBPATH is empty" decision but it was long
> enough ago that I can't say 100% for sure.
>
> I agree that AWKPATH and AWKLIBPATH should behave identically.
>
> I think that gawk should always check "." before running the path search.
>
> A case could be made that if AWKPATH is in the env but empty that gawk
> should not do a path search.  OTOH, it's been the way it is for 20+ years.

I'm less certain that we should always check "." before searching AWKLIBPATH.
While this is intuitive behavior for AWKPATH source code, it seems not so
obvious to me for binary shared libraries.

Thoughts?

Regards,
Andy