Maybe another bug or for whatever reason it may be intended:
I'm using a library to use the MCP2515 CAN controller. The lib was originally developed by seeedstudio GitHub - Seeed-Studio/Seeed_Arduino_CAN: Seeed Arduino CAN-BUS library - MCP2518FD&MCP2515&MCP2551) to support their CAN shield (CAN-BUS Shield V2.0 - Seeed Wiki) and later enhanced by someone else. I'm now doing some rework for my own purposes. The lib contains 2 issues, one about an unused variable in a function and another one about a function which should return a value and returns (void). The first one is OK, but the 2nd one should IMHO be an error and not a warning.
When I run "Verify" those errors only show up the very first time. When I run "Verify" again without making any changes to the code, the warnings are gone.
When I close the IDE and open it again, then load the sketch again and run "Verify" again hte errors are never shown again. I re-tried this using a different target board, and still no errors...
Not sure if this is a GCC issue or an Arduino issue.