Avoid collisions between parallel installations of Cygwin

Christopher Faylor cgf-use-the-mailinglist-please@cygwin.com
Thu Oct 15 17:27:00 GMT 2009

On Thu, Oct 15, 2009 at 12:28:02PM -0400, Charles Wilson wrote:
>>> One other thought: what about developing the cygwin DLL itself? Every
>>> time you build the DLL and use it without installing (say, in the test
>>> suite) you get yet another entry -- or an update to the existing entry
>>> in the registry corresponding to your customary cygwin DLL build
>>> directory -- in the registry?  That seems awkward.  Maybe (borrowing the
>>> idea above), the cygwin0.dll could be built with the special resources
>>> section indicating "portable" (e.g. don't touch the registry) use, and
>>> during 'make install' when cygwin1.dll is created the special tool could
>>> be used to modify that value...
>Err...no.  I've thought about this some, and the "special tool" would be
>really really difficult. There's no API for writing resources to a
>separate image. You can LoadLibrary a DLL, and access an in-memory copy
>of its resources.  You might even be able to write to that memory
>location.  But you really can't modify the disk image using a public
>API.  So, you'd basically be left with a tool that must reverse-engineer
>the disk image after it is linked, locate the correct symbol, find the
>address...yuck. No thanks.

We actually have a tool like this at work which finds a symbol and modifies
it.  It can be done.  I'll investigate more when I get back.


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