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Message-ID: <3AB14F6C.E15E2D61@dot21rts.com>
Date: Thu, 15 Mar 2001 18:25:33 -0500
From: Andy Helten <andy DOT helten AT dot21rts DOT com>
MIME-Version: 1.0
To: cygwin AT cygwin DOT com, "Larry Hall (RFK Partners, Inc)" <lhall AT rfk DOT com>
Subject: Shell's "eval" doesn't behave when running a non-cygwin compiler
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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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