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Subject: Re: Use a default path in exec*p*() if PATH is unset?
To: cygwin AT cygwin DOT com
References: <d1bc1cea-2438-5e03-e84c-8d4e169d9592 AT t-online DOT de> <ae107c01-bea2-b562-1bc6-f5ba188eeba9 AT towo DOT net> <7b94712a-465d-421b-bc76-720e443708d3 AT t-online DOT de> <6991638b-2400-dacd-28ee-e2d2c9d91ed4 AT gmail DOT com>
From: Christian Franke <Christian DOT Franke AT t-online DOT de>
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Date: Tue, 11 Apr 2017 21:02:22 +0200
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cyg Simple wrote:
>
>    -i, --ignore-environment  start with an empty environment
>
> A relative use of the executable will not be found if the environment is
> empty.

Not necessarily (see Linux, *BSD, ...). POSIX says this is 
"implementation-defined" - under the assumption that 'env' uses execvp() 
which is the case for the GNU coreutils version.


>> Interestingly the approach in newlib/libc/posix/execvp.c differs from
>> Cygwin and others:
>> execvp() with PATH unset calls execv(). This has the same effect as
>> execvp() with PATH set to current directory only.
>>
> Why do you assume that this is an issue with execvp?

I never did (otherwise this would be a thread on cygwin-patches list).

The above only means that it is IMO interesting that the Cygwin source 
package contains two implementations of execvp() which handle the unset 
PATH situation differently.


> The user should
> not expect that an undefined behavior behaves the same way on other
> systems.

Of course. But even then it is a reasonable question which possible 
alternative should be implemented by Cygwin. Cygwin homepage says "Get 
that Linux feeling, ...". So "implementation-defined" behavior should 
possibly be close to Linux :-)

Christian


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