Re: Shell's "eval" doesn't behave when running a non-cygwin compiler

["Robert Collins" <robert dot collins at itdomain dot com dot au>]

Try a recent snapshot. There was a related thread recently (cygwin not
waiting for non-cygwin child process's) that IIRC Chris checked in a fix
for.

Rob


----- Original Message -----
From: "Andy Helten" <andy.helten@dot21rts.com>
To: <cygwin@cygwin.com>; "Larry Hall (RFK Partners, Inc)"
<lhall@rfk.com>
Sent: Friday, March 16, 2001 10:25 AM
Subject: Shell's "eval" doesn't behave when running a non-cygwin
compiler


> Hello,
>
> I've posted this problem to this newgroup a couple times
> (first without an strace listing and then with an strace
> listing), under the subject: "VxWorks' GNU cross-compiler in
> the Cygwin environment".  However, I have only gotten one
> response and was hoping if I simplified the problem scenario
> and changed the "Subject:" line, it might be more appealing
> to look at.
>
> The following simple shell script can be used to produce the
> problem:
>
> #!/bin/sh
> rm -f conftest
> ac_link="c++ppc -nostdlib -nostdinc -c -o conftest
> conftest.cpp"
>
> if { (eval echo \"$ac_link\"); (eval $ac_link); } then
>   echo "Compile succeeded (or did it?)"
> else
>   echo "Compile failed!"
> fi
>
> if test -s conftest; then
>   echo "1. The output is available!"
> else
>   echo "1. The output is NOT available!"
> fi
>
> sleep 2
>
> if test -s conftest; then
>   echo "2. The output is available!"
> else
>   echo "2. The output is NOT available!"
> fi
>
>
>  If I run the above shell script using 'bash' or 'sh', I get
> the following output:
>
> c++ppc -nostdlib -nostdinc -c -o conftest conftest.cpp
> Compile succeeded (or did it?)
> 1. The output is NOT available!
> 2. The output is available!
>
> Also, I have found a work around using the following perl
> script:
>
> #!/usr/bin/perl
> eval `c++ppc @ARGV`;
>
> Apparently, Perl's "eval" waits for the compiler to finish
> before continuing and 'sh' waits for the cygwin perl to
> finish, so this at least serializes things.  So the output
> from the shell script when using the perl script as the
> "compiler" is what you would expect:
>
> c++ppc_cygwin_workaround -nostdlib -nostdinc -c -o conftest
> conftest.cpp
> Compile succeeded (or did it?)
> 1. The output is available!
> 2. The output is available!
>
> However, the downside is that I don't get the return value
> from the compiler.  So if a compile fails, it does not stop
> the build.
>
> The question I have:  can cygwin 'sh' or 'bash' be used to
> spawn non-cygwin utilities (compilers)?  From my experience,
> the answer is NO.  Is it even possible to get 'sh' to
> recognize and wait for a non-cygwin process spawned by
> 'eval'?  Could someone please answer these questions?  I can
> provide an strace of the above situation if anyone wants
> it.  And yes, I would be willing to at least look at the
> problem, but first would like someone to at least
> acknowledge this is problem and/or classify this behavior
> (normal/not normal/user error). OR, if there is another
> Bourne compatible shell that works with the cygwin
> environment could someone point me to it?
>
> Thanks,
> Andy
>
>
>
> --
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>


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