Fix some lit test ResourceWarnings on Windows

[amccarth]

Summary

When running LLDB lit tests on Windows, the system selects a debug version of Python, which was issuing lots of
ResourceWarnings about files that weren't closed. There are two kinds of them, and each test triggered one of each.

This patch fixes one kind by ensuring TestRunner explicitly close the temporary files created for routing stderr. This is important on Windows but has no net effect on Posix systems.

The remaining ResourceWarnings are more elusive; the bug may lie in the Python library subprocess.py, and it may be Windows-specific.

[stella.stamenova]

LGTM

[delcypher]

llvm/utils/lit/lit/TestRunner.py

772 ↗

(On Diff #203919)

What does this change have to do with closing files?

[amccarth]

llvm/utils/lit/lit/TestRunner.py

772 ↗

(On Diff #203919)

That was a leftover change from the diagnosis phase. The resource leak was always reported on the following line (773), so a lot of the attention was focused in this region even though the actual fix was below.

I was just trying to leave the code a little cleaner than I found it by eliminating the unused variable. But, you're right, it's not relevant to the point of this patch, so I'll undo it.

llvm/trunk/utils/lit/lit/TestRunner.py

for i in range(len(procs) - 1):
         else:
             err = ''
         procData[i] = (out,err)
 
     # Read stderr out of the temp files.
     for i,f in stderrTempFiles:
         f.seek(0, 0)
         procData[i] = (procData[i][0], f.read())
+        f.close()
 
     exitCode = None
     for i,(out,err) in enumerate(procData):
         res = procs[i].wait()
         # Detect Ctrl-C in subprocess.
         if res == -signal.SIGINT:
             raise KeyboardInterrupt