Well, that escalated quickly :-) I think I should clarify my use case that resulted in raising this bug. 1. Create a fresh hg clone, say, ~/hg/cpython-3.2. 2. Make it readonly: `zfs set readonly=on tank/home/cpython/hg/cpython-3.2` 3. cd /tmp/cpython-3.2-build 4. /home/cpython/hg/cpython-3.2/configure --srcdir=/home/cpython/hg/cpython-3.2/configure So, my patches address that use case. The thing I like about the approach above is that I can set the source directory to readonly immediately -- I don't have to do an intermediate ./configure in that directory in order to generate a Makefile so I can `make touch`. (Side note: I'm almost certain `make touch` wouldn't work for my use case.) Richard: what was your use case? What steps did you take that resulted in getting typeslots.inc and _sysconfigdata.py written to? ....although I just tried an out-of-tree build with 'default' using the exact steps above and got the same error with _sysconfigdata.py. Martin: I think I understand your arguments, and I (think) I agree with them. Especially your last point with regards to always running ASDLGEN. I think I'm +1 on reverting and trying the '-' approach originally used by Neil.