execvp* and spawnvp* react differently to same PATH environment variable

execvp* and spawnvp* react differently to same PATH environment variable

[donpedro.tdcadsl.dk via cygwin]

Hi all, 

While working on something i noticed that execvp* and spawnvp* behave differently with regards to $PATH, which i think is not correct. 

----------------------------------------------

1) The execvp* functions are called like this: 

return spawnve ( _P_OVERLAY | _P_PATH_TYPE_EXEC , 
   find_exec ( file , buf , "PATH" , FE_NNF ) ? : "" , 
   argv , envp );

This calls find_exec() with FE_NNF, which causes the path to be NULL if not found in $PATH.

This later causes cygwin to fail correctly if the program is not in $PATH.

----------------------------------------------

2) The spawnvp* functions are called like this: 

return spawnve (mode | _P_PATH_TYPE_EXEC, find_exec (file, buf), argv, cur_environ ());

This does _not_ calls find_exec() with FE_NNF which causes the path to be the posix form, as it is not found in path.

This later causes cygwin to find the program even though it was not in $PATH which seems wrong.

----------------------------------------------

This seems like a bug in spawnvp* functions unless i am missing something? 

Any thoughts?

Thanks,

/pedro







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Re: execvp* and spawnvp* react differently to same PATH environment variable

[Ken Brown]

On 10/7/2019 4:51 PM, donpedro.tdcadsl.dk via cygwin wrote:
> Hi all,
> 
> While working on something i noticed that execvp* and spawnvp* behave differently with regards to $PATH, which i think is not correct.
> 
> ----------------------------------------------
> 
> 1) The execvp* functions are called like this:
> 
> return spawnve ( _P_OVERLAY | _P_PATH_TYPE_EXEC ,
>     find_exec ( file , buf , "PATH" , FE_NNF ) ? : "" ,
>     argv , envp );
> 
> This calls find_exec() with FE_NNF, which causes the path to be NULL if not found in $PATH.
> 
> This later causes cygwin to fail correctly if the program is not in $PATH.
> 
> ----------------------------------------------
> 
> 2) The spawnvp* functions are called like this:
> 
> return spawnve (mode | _P_PATH_TYPE_EXEC, find_exec (file, buf), argv, cur_environ ());
> 
> This does _not_ calls find_exec() with FE_NNF which causes the path to be the posix form, as it is not found in path.
> 
> This later causes cygwin to find the program even though it was not in $PATH which seems wrong.
> 
> ----------------------------------------------
> 
> This seems like a bug in spawnvp* functions unless i am missing something?

I think you're probably right.  The use of FE_NNF in execvp* was introduced in 
commit 6d63272b.  I suspect it was just an oversight that the spawvp* functions 
weren't changed in the same way.  I'll send a patch to the cygwin-patches list 
to fix this.  When Corinna returns, she can tell us whether there's some reason 
that spawnvp should be different from execvp.

Ken

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Re: execvp* and spawnvp* react differently to same PATH environment variable

[Peter Dons Tychsen via cygwin]

Hi Ken,

> I think you're probably right.  The use of FE_NNF in execvp* was
> introduced in 
> commit 6d63272b.  I suspect it was just an oversight that the spawvp*
> functions 
> weren't changed in the same way.  I'll send a patch to the cygwin-
> patches list 
> to fix this.  When Corinna returns, she can tell us whether there's
> some reason 
> that spawnvp should be different from execvp.

Excellent. Thanks for the fast response. I will keep an eye out for
when it lands.

Thanks,

/pedro

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