From:	lanford AT frihes61 DOT bitnet
Date:	Thu, 10 Sep 92 16:10:17 +0200
To:	djgpp AT sun DOT soe DOT clarkson DOT edu
Subject:	Repeated writes to cerr causes catastrophic thrashing

Has anyone else observed the following?

The simple program

++++++++++++++++++++++++++++++++++++++++++++++++++
#include <iostream.h>

main()

{
  int i;
  for (i = 0; i <30; i++)
      cerr << "The quick brown fox jumps over the lazy dog" << "\n";
}
++++++++++++++++++++++++++++++++++++++++++++++++++++++

crashes. More precisely: After printing fourteen lines it stops
printing, and -- apparently -- begins frantically paging.  If left to
itself -- and if the swap file is on a smallish (2 Meg) ram disk -- it
will before too long print out

    Fatal! disk full writing to swap file

and terminate. This does NOT happen if the print instruction is replaced by

    cerr << "The quick brown fox jumps over the lazy dog\n"

(i.e., the two strings concatenated) or by

    cout << "The quick brown fox jumps over the lazy dog" << "\n";

(i.e., cout instead of cerr.)

Versions, etc:
  gcc version 2.2.2: Loaded from djgcc222.zip, djgpo222.zip,
  djgas138.zip, djdev108.zip (and, I believe, nothing else)
  Although I haven't checked directly, there is reason to believe that
  gcc 2.01 will give the same result, but gcc 1.39 will not. (Reason:
  The above simple program resulted from analyzing a reproducible crash
  of a bigger project. The same crash occurred with gcc 2.01, but not
  with 1.39.)

Environment:
  Most of the exploration was done on a Toshiba T2200SX with
  10 Megs of memory and the 386Max memory manager. The behavior doesn't
  change in the absence of memory management. Furthermore, the whole
  phenomenon seems to be machine independent: Various pieces were repeated
  on a number of different machines, and the place where thrashing begins
  is always independent of machine -- in particular, doesn't depend on the
  amount of memory.

Oscar E. Lanford
lanford AT frihes61 DOT bitnet     (until October 6)
lanford AT math DOT ethz DOT ch        (thereafter)

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