[Tcl-bugs] [ tcl-Bugs-699739 ] app can overrun console buffer on Windows

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Bugs item #699739, was opened at 2003-03-07 16:42
Message generated for change (Comment added) made by davygrvy
You can respond by visiting: 
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Category: 27. Channel Types
Group: obsolete: 8.4.2
Status: Open
Resolution: None
Priority: 5
Submitted By: Kevin B KENNY (kennykb)
Assigned to: David Gravereaux (davygrvy)
Summary: app can overrun console buffer on Windows

Initial Comment:
If an application configures a very large buffer on stdout, and then writes
a large amount of data to the console on Windows, the write fails with

error writing "stdout": not enough memory

A script that illustrates the problem is:

fconfigure stdout -buffering full -buffersize 262144
for { set i 0 } { $i <= 10000 } { incr i } {
    puts ----------------------------------------------------------------------
}

It's reasonable for the write to block, but this failure is bizarre.

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>Comment By: David Gravereaux (davygrvy)
Date: 2004-06-02 12:24

Message:
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It seems the upper limit -buffersize is 0x7FFF.  One over that 
and WriteFile fails with ENOMEM.

I can't think of a way to fix this aside from adding a way for 
drivers to intercept requests to change the buffersize.

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Comment By: David Gravereaux (davygrvy)
Date: 2004-06-01 02:50

Message:
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Just put tcl in the debugger to look at this.

WriteFile itself is failing in ConsoleOutputProc().  I think the 
summary of this problem is that the other end can't accept a 
buffer this big and rather than soaking up some of it, it just 
barfs.

I don't know if there is an easy way to fix this.  Even if we 
knew the limit ahead of time (maybe GetConsoleBufferInfo 
could get us the answer?) we have no way for the driver to 
intercept a setting of the buffersize from the driver side.

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