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Subject: Re: Is it possible to define the root directory in a cross compiled
 program
To: cygwin AT cygwin DOT com, Brian Inglis <Brian DOT Inglis AT SystematicSw DOT ab DOT ca>
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 <9d339f8b-83ff-8b9c-b2fe-1c6fa4b2a92d AT SystematicSw DOT ab DOT ca>
From: Eliot Moss <moss AT cs DOT umass DOT edu>
Message-ID: <472d5b4e-1916-eb79-cf3d-44f43b5f8b5d@cs.umass.edu>
Date: Tue, 5 Jan 2021 08:34:39 -0500
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On 1/4/2021 10:17 PM, Brian Inglis wrote:
> On 2021-01-04 18:34, Roger Kaufman wrote:
>> When I cross compile the following program, opening /dev/null fails and instead the whole install 
>> path of /cygwin64/dev/null is visible.
>>
>> Is there a way to make fopen respect / as the root directory in a cross compiled program for windows?
>>
>> example output...
>>
>> Roger AT interocitor:~
>> $ x86_64-w64-mingw32-g++ -o writenull.exe write2null.cc
>>
>> Roger AT interocitor:~
>> $ writenull.exe
>> /dev/null did not succeed
>>
>> Roger AT interocitor:~
>> $ gcc -o writenull write2null.cc
>>
>> Roger AT interocitor:~
>> $ writenull
>> /cygwin64/dev/null did not succeed
>>
>> C Code that was compiled...
>>
>> #include <cstdio>
>>
>> int main(int argc, char **argv)
>> {
>>    FILE *errfile1 = fopen("/dev/null", "w");
>>    if (!errfile1) // must be a valid pointer
>>      errfile1 = stderr;
>>
>>    FILE *errfile2 = fopen("/cygwin64/dev/null", "w");
>>    if (!errfile2) // must be a valid pointer
>>      errfile2 = stderr;
>>
>>    fprintf(errfile1, "/dev/null did not succeed\n");
>>    fprintf(errfile2, "/cygwin64/dev/null did not succeed\n");
>>
>>    return 0;
>> }
> 
> It's a Windows program - it can do whatever you program it to do!
> On Windows the device is NUL, the root is the drive root C:\,
> and anything else depends on the Windows subsystem.
> 
> To do otherwise you have to program it to emulate the Cygwin emulation,
> or build it as a Cygwin program using the Cygwin toolchain.

Is there a Windows equivalent to chroot (either the program or the library/system call)?

Regards - Eliot
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