Current PCB tools generally export gerbers in higher precision than GerbV exports RS274X files in. In rare circumstances, the start and end coordinates of an arc can be close enough that this loss of precision causes GerbV to round them to the same coordinate. This makes the arclength 0, and the arc is then treated as a full circle.
If this occurs near traces or ground planes, then it generally results in the gerbers having a short, resulting in fabrication of the board to be incorrect. The attached test case contain an affected arc. Saving the 3.6 formatted gerbv with standard GerbV will result in the short occuring.
This patch simply adjusts the export output to 3:6 format, which is equal to or higher than most tools output. This avoids the precision loss, and thus the arc rounding bug.
Good job! I'd like to see this patch applied (I use 3:5 format)
Last edit: Bryce Nesbitt 2016-07-10
Applied as git dbd8a4f444d516e9ed867576c022f2492b920f4f