Buffer gives incorrect result for negative distance

[jdmarsh]

I have a polygon where I want to buffer inwards using a negative distance. The result I get is incorrect.

Polygon(red) and then the result of the buffer command "output" (green).

The expected result of this buffer is for the output to be empty, instead the green triangle is huge.

• At the top left corner, it's buffered inwards but not by the -1.8 units specified.
• At the top right corner, the output goes outside the outer boundary of the polygon
• The center should certainly not be filled in

The code to generate this can be found here:
https://godbolt.org/z/18sq55oTG

[barendgehrels]

Fixed recently in acaed28
I will create a unit test

[barendgehrels]

Thanks for the report.
For the record, the PR was #1248