Previously, pressing 'cancel' in the verification window would leave a dangling scyther backend process.
Now the process gets correctly killed.
The following changes enable this:
- External processes are no longer invoked through the shell (otherwise they are subprocesses of the shell and cannot be reliably killed cross-platform).
- The 'safeCommand' procedure now has a hook for passing opened Popen objects.
- The GUI stores and kills the Popen objects on cancel or window close.
To do: an alternative interface for this in 'safeCommand' could expose a 'killMe' method through a callback; this might be cleaner in the long term.
Before, we were using both __file__ as well as sys.argv[0] to determine the base directory
for Scyther, and we were not taking symlinks into account.
By using the inspect module, we can consistently pick the current frame and derive
the file from that, then use realpath to strip symlinks.
Cached data is stored in:
Cache/XX/YYYYY.out (stdout)
Cache/XX/YYYYY.err (stderr)
Where XX^YYYYY is the sha256 hexdigest of the concatenation of the input spdl and
the arguments.
