On Aug 22 16:46, Earnie Boyd wrote: > On Thu, Aug 22, 2013 at 1:14 PM, Corinna Vinschen wrote: > > > > When execveing a Cygwin process, a lot of data is submitted via shared > > memory, via data copying, and via a special parameter to the > > CreateProcess call with the mysterious name "lpReserved2". > > > > One problem is the differences in basic datatypes, which results in > > incompatible datastructures between 32 and 64 bit. While this could be > > worked around, this doesn't help for the shared memory stuff, which > > depends on the installation path of the cygwin DLL. The Cygwin DLL in > > C:\cygwin1 would use a different name for the shared mem regions than > > the Cygwin DLL installed into C:\cygwin2, independent of the target > > architecture. This is by design since Cygwin 1.7. One effect: No tty > > sharing. > > > > Since you know that the DLL regions are different what about execing > the process as if it were a windows native process? I know you loose > the ability to do the parent/child relationship but it isn't any worse > than spawning a native process.
Actually, Cygwin alread did that. When checking the executable to run for being a Cygwin process, executables with the wrong bitsize were treated as non-Cygwin executables. The actual problem was that we always propagate a child_info_spawn structure to the child via STARTUPINFOW::lpReserved2, no matter what kind of executable we execute. The header of this structure is identical on 32 and 64 bit, so the child process recognized it as a child_info_spawn block, regardless of the target size of parent and child. But then the rest of this child_info_spawn differs a lot due to different datasizes. Since it neither makes sense to propagate the Cygwin-specific child_info_spawn block to native processes, nor to Cygwin processes with a different bitsize, I just disabled this, so you can now start 32 bit Cygwin processes from 64 bit Cygwin processes and vice versa, starting with the snapshots I'm just generating. I just hope this won't lead to more confusion if 32 bit processes started from 64 bit (or vice versa) don't act as expected in some circumstances. Here's a typical 32 bit bash started from 64 bit tcsh in a 64 bit mintty, for instance: tcsh-64$ /cygdrive/c/cygwin/bin/bash -i bash: cannot set terminal process group (-1): Inappropriate ioctl for device bash: no job control in this shell $ Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Maintainer cygwin AT cygwin DOT com Red Hat
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