Open Bug 573306 Opened 13 years ago Updated 8 months ago

stdout and stderr get tangled on Windows (when using automation.py?)

Categories

(Testing :: General, defect)

Product:
Testing
Component:
General
Platform:
x86
Windows 7
Type:
defect

Tracking

(Not tracked)

People

(Reporter: jruderman, Unassigned)

References

(Depends on 1 open bug)

Details

Attachments

(3 files)

r.xhtml
588 bytes, application/xhtml+xml
Details
crashtests.list
13 bytes, text/plain
Details
example output
424 bytes, text/plain
Details 
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.
Attached file r.xhtml — 

    
    

    
  

      
      
      
      

        Attached file
          
        crashtests.list
        — 
      

    


  

    
    

    
  

      
      
      
      

        Attached file
          
        example output
        — 
      

    


  

    
    

    
  
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.

    
  
Blocks: 809240

    
  
Severity: normal → S3

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