Re: Improving xtrace output from subshells

Re: Improving xtrace output from subshells

[Harald van Dijk]

On 29/04/2019 23:55, Harald van Dijk wrote:
> On 29/04/2019 15:44, Vadim Zeitlin wrote:
>> On Sat, 27 Apr 2019 22:58:23 +0100 Harald van Dijk 
>> <harald@gigawatt.nl> wrote:
>> HvD> It wastes memory: the code should be re-worked so that output and
>> HvD> preverrout share the same buffer, given that there can never be 
>> pending
>> HvD> output for one when the other is being written to.
>>
>>   I'm a bit worried about this one, it doesn't seem completely obvious 
>> to me
>> that the 2 objects can't be used at the same time.
> 
> It's indeed not completely obvious, but all bits that print to output 
> will flush the buffer when they're done, before a next command starts 
> executing, before the next command requires an xtrace string to be 
> printed. It's usually the flushall() in evalbltin() that handles this.

I have managed to verify that using a single buffer for all streams 
(output, errout and preverrout) works well and simplifies logic so that 
the shell with that change is actually smaller than the one without it. 
I do not know whether there would be interest in getting that in dash.

Cheers,
Harald van Dijk