Why is sformat and formattedWrite (appender) allocating GC mem here?
anonymous at example.com
Sat Aug 31 21:12:32 UTC 2019
On 31.08.19 14:07, cc wrote:
> I'm guessing it's allocating a string first to write the contents
> of the array and then inserting that string into the buffer I supplied.
> Is there no way to have it skip this step and just write each element
> (plus the joining punctuation, etc) directly into the buffer?
`formatElement` does something like that. It writes the string into a
temporary buffer while looking for invalid Unicode. When it finds some,
the temporary is discarded and the whole string is formatted
differently. When the string is a-ok, the data is copied over to the
I'm not sure if that's the best approach, though. The temporary buffer
and the string copy are costly.
There is also a closure being allocated for no reason in `sformat`
itself. The compiler isn't smart enough to see that it's not really needed.
I've made a pull request to get rid of those allocations:
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