Re: verbose testsuite output contains 1M newlines

[Eric Blake]

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[adding autoconf; this is an interesting question about autotest]

According to Ralf Wildenhues on 11/23/2008 6:23 AM:
> Hello Eric,

Hi Ralf,

> 
> running
>   make check-local TESTSUITEFLAGS=-v
> 
> on M4 (git master) produces lots of output on GNU/Linux/bash.  More
> precisely, the AT_CHECK in builtins.at:470 causes 1024*1024 newlines
> to be output, and I think there are more instances later.  Can this
> easily be avoided?

Hmm, this particular test _has_ to generate more than a megabyte of output
in order to trigger the code path in m4 being tested (namely, that m4
starts using temporary files after it collects enough in-memory diversion
output).  The problem stems from the fact that by default, when you
specify [stdout] as the third argument to AT_CHECK, autotest emits code
that both collects the file stdout (good) and copies the resulting file
into the log (annoying), and when -v is in effect, tees that copy to the
terminal (bad).  I think the idea behind this decision was that
testsuite.log should be self-contained, with everything needed to
reproduce why a test failed.

The point of specifying [stdout] is that we plan on processing the
resulting output file later on, so maybe we should quit trying to copy the
captured file into the logs.  Maybe we should revisit this, and change it
so that the file is just collected, with nothing output into the log.  Or
even add a heuristic, where only the first and last 10 lines of the
resulting file are output into the log.  If the test passed, then the log
doesn't need megabytes of information; and if the test fails, hopefully
trimming out the middle of the file from the log still leaves enough
information in the log to help diagnose what went wrong; the full file
will still be available in testsuite.dir/nnn/stdout if the log was
insufficient by itself.

> 
> Hmm, maybe this is introduced by some Autotest changes in Autoconf even.

No, I think this behavior is present even with 2.62, before we started
using functions in autotest (although I haven't tested yet).

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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