When you upgrade the Cygwin openssl package (or possibly any package, but the openssl package has caused the most problems for me) you are sometimes hit with mysterious-looking errors that go away if you run
rebaseall. So I have taken the habit of always making sure that I install the
ash packages when I do the initial Cygwin installation, and then run
rebaseall after I upgrade any components.
rebaseall can be a bit tricky. The only Cygwin program that can be running at the time is the
ash shell. So first of all you need to shut down any long running processes like
sshd, close all Cygwin prompts and so on. Next you need to start the plain Windows Command Prompt (if you normally run as unprivileged user but install software as Administrator, then you want to start the prompt by right clicking the icon and selecting Run As… and choosing an administrator account). Then type the following commands (assuming default Cygwin installation location):
cd \cygwin\bin ash PATH=. rebaseall -v
This should result in several lines of output similar to:
/usr/lib/xyz.dll new base = 1234, new size = 123
After that you can restart any long running processes, start the normal Cygwin shell and all should be good.