[Lilypond-auto] [LilyIssues-auto] [testlilyissues:issues] #5741 Parse inline scheme using per-expression port

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Not referencing the issue in the commit message makes it harder to find the issue in the tracker. After a few patchy runs It appears like this change may cause a massive impact on performance at least for a Guile-1.8 based compilation. A patchy run on a mostly unloaded machine previously took about 40 minutes on my computer. Now it appears to be more like 52 minutes. Considering that non-trivial amounts of time also get spent by GCC and Ghostscript, that seems rather troubling. Have you benchmarked the Guile-1.8 case (where performance problems may be less masked by startup times etc)?

If we can verify that on a Guile-1.8 compilation the slow-down is like this (I'd guess that the slowdown when reduced to just the LilyPond contribution could be about 30%), I think we should not include a version of this in 2.21.0 but release at least one unstable version without it so that actual users have a chance to report slowdowns in case they reappear.

I don't think this patch actually fixes any Guile-2 problem when viewed against the current version of master as opposed to what was in master when you designed it?

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[issues:#5741] Parse inline scheme using per-_expression_ port

Status: Fixed
Labels: Fixed_2_21_0
Created: Fri Feb 07, 2020 02:52 PM UTC by Han-Wen Nienhuys
Last Updated: Sat Feb 22, 2020 11:29 AM UTC
Owner: Han-Wen Nienhuys

Introduces a throw-away string port, Overlay_string_port, which makes
a port out of a random section of a C string. It does not own the
string, so there is no overhead in creating and discarding the ports
during parse time.

For GUILE v2, Overlay_string_port uses UTF-8 encoding, so UTF-8
encoded string constants within the Scheme constants are interpreted
as Unicode correctly.

This obviates the string port that Source_file carries along.

This commit fixes a problem with GUILE 2.2.6, where LilyPond
calculates offsets in the source file as bytes, while GUILE interprets
the source file as UTF-8 encoded Unicode. As a result, files with
Unicode before embedded scheme break completely.

https://codereview.appspot.com/557330043

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