mintty fails to start

mintty fails to start

[Emember MemberUS via cygwin]

This is a minor issue and probably not typical, but could be of interest to cygwin developers/maintainers.

Problem: 
After building a 3-party cross-toolchain (unrelated to cygwin), mintty is no longer able to start.
While a few mintty windows that were still open worked ok, any NEW mintty window just flashed and immediately closed itself. 

Solution: 
Re-installation of cygwin from scratch is undesirable because current installation already has multiple customizations. 
Initial research yielded nothing - no error message, or hint of any kind, and discussion forums offered no clue either. 
The cause of the issue happened to be an empty file /bin/bash. It is currently unclear where it came from (could be a side 
effect of a build), but it is not part of standard cygwin installation. Once this empty file is deleted, mintty is able to start again. 


Suggestion: produce an error message that would help identifying this problem when mintty starts. 
NOTE: this issue happens only in cygwin, and only when both files are present: /bin/bash.exe and empty /bin/bash.
If no bash is present, mintty issues a correct error message.

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Re: mintty fails to start

[Thomas Wolff]

Am 19.01.2017 um 16:25 schrieb Emember MemberUS via cygwin:
> ...
>
> Suggestion: produce an error message that would help identifying this problem when mintty starts.
> NOTE: this issue happens only in cygwin, and only when both files are present: /bin/bash.exe and empty /bin/bash.
> If no bash is present, mintty issues a correct error message.
One interesting test case may be to remove the x bit from the empty bash 
file, to see that mintty handles invocation errors properly.
The issue is that invocation of an empty file (provided that the x bit 
is set) is not considered an error in a Linux environment, and thus on 
cygwin, so the exec system call does not report an error in the first place.
There is nothing that can be done about it, the behaviour is correct.
------
Thomas

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Re: mintty fails to start

[Emember MemberUS via cygwin]

----- Original Message -----
From: Emember MemberUS <ememberus@yahoo.com>
To: "cygwin@cygwin.com" <cygwin@cygwin.com>
Sent: Thursday, January 19, 2017 10:25 AM
Subject: mintty fails to start

This is a minor issue and probably not typical, but could be of interest to cygwin developers/maintainers.

Problem: 
After building a 3-party cross-toolchain (unrelated to cygwin), mintty is no longer able to start.
While a few mintty windows that were still open worked ok, any NEW mintty window just flashed and immediately closed itself. 

Solution: 
Re-installation of cygwin from scratch is undesirable because current installation already has multiple customizations. 
Initial research yielded nothing - no error message, or hint of any kind, and discussion forums offered no clue either. 
The cause of the issue happened to be an empty file /bin/bash. It is currently unclear where it came from (could be a side 
effect of a build), but it is not part of standard cygwin installation. Once this empty file is deleted, mintty is able to start again. 


Suggestion: produce an error message that would help identifying this problem when mintty starts. 
NOTE: this issue happens only in cygwin, and only when both files are present: /bin/bash.exe and empty /bin/bash.
If no bash is present, mintty issues a correct error message.


    ... 

    Suggestion: produce an error message that would help identifying this problem when mintty starts. 
    NOTE: this issue happens only in cygwin, and only when both files are present: /bin/bash.exe and empty /bin/bash. 
    If no bash is present, mintty issues a correct error message. 


    One interesting test case may be to remove the x bit from the empty bash file, to see that mintty handles invocation errors properly. The issue is that     invocation of an empty file (provided that the x bit is set) is not considered an error in a Linux environment, and thus on cygwin, so the exec system     call does not report an error in the first place. 
    There is nothing that can be done about it, the behaviour is correct. 
    ------ 
    Thomas 



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


Correction:
replace <produce an error message> above with
<allow logging of exec call(s)>

Current behavior may be correct, but it makes cygwin vulnerable to such hard-to-detect configuration problems.

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Re: mintty fails to start

[Thomas Wolff]

Am 20.01.2017 um 22:19 schrieb Emember MemberUS via cygwin:
>      ...
>
>      Suggestion: produce an error message that would help identifying this problem when mintty starts.
>      NOTE: this issue happens only in cygwin, and only when both files are present: /bin/bash.exe and empty /bin/bash.
>      If no bash is present, mintty issues a correct error message.
>
>
>      One interesting test case may be to remove the x bit from the empty bash file, to see that mintty handles invocation errors properly. The issue is that     invocation of an empty file (provided that the x bit is set) is not considered an error in a Linux environment, and thus on cygwin, so the exec system     call does not report an error in the first place.
>      There is nothing that can be done about it, the behaviour is correct.
>      ------
>      Thomas
>
>
> ---------------------------------------------------------
>
> Correction:
> replace <produce an error message> above with <allow logging of exec call(s)>
>
> Current behavior may be correct, but it makes cygwin vulnerable to such hard-to-detect configuration problems.
Please describe precisely what you have in mind. A log output before 
invoking the client program would normally not be desired. You can keep 
mintty from closing with option `-h alw` but you wouldn't see anything now.
Also this issue does not make cygwin vulnerable because on invocation of 
an empty program nothing happens.
------
Thomas

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