Open Bug 573306 Opened 11 years ago Updated 4 years ago
stdout and stderr get tangled on Windows (when using automation
Steps to reproduce: 1. Save r.xhtml and crashtests.list to your desktop. 2. Load the crashtests.list using runreftest.py. Result: "XXB" and sometimes "XXA" (going to stdout) get tangled with stack traces (going to stderr). There will be part of a line of a stack trace, followed by "XXB\n", followed by the rest of the line of the stack trace. Expected: "XXA" and "XXB" should always appear by themselves on a separate line.
For fuzzing it's important for me to be able to process the output from Firefox. But I think I can work around this issue by not printing assertion stacks while fuzzing.
This is how Windows works: the standard streams are character-buffered. Unless you mean that automation should save stdout/stderr to files separately and then dump them, which seems a bit strange.
What can programs do to make their output deterministic? Not use stderr at all?
(In reply to comment #5) > This is how Windows works: the standard streams are character-buffered. Unless > you mean that automation should save stdout/stderr to files separately and then > dump them, which seems a bit strange. Allowing them to get tangled is strange too!
Would some carefully placed fflush() calls help?
How should I work around this for fuzzing, if turning off assertion stacks isn't enough? Add fflush calls to Firefox? Add a mode to automation.py where stdout and stderr go to different pipes/files?
We could probably fix this in automation.py by reading stdout and stderr separately, and line-buffering them. That would complicate things a bit, but not terribly, I think. It looks like we probably hit this in bug 740242, where the DOMWINDOW spew and assertion output get intermingled, which is breaking our log parsing. Also: we're planning on moving all our test harnesses away from automation.py and onto the mozbase modules, so maybe we should just fix this there.
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