> - The project already exists, and now you need to refactor out all the compile-time errors in order to move forward (time-consuming).
Use a static analysis tool with proper, non-brittle tracking of new vs old findings (including proper move and copy file tracking) and forbid new findings, e.g. by preventing offending code from being merged to master with tools like Gitlab, Bitbucket, what have you. Works very well in practice. Bonus points if the tool can also tell you when you modified a function and didn't clean up the old findings in there. Then you can really enforce incremental improvement.
Use a static analysis tool with proper, non-brittle tracking of new vs old findings (including proper move and copy file tracking) and forbid new findings, e.g. by preventing offending code from being merged to master with tools like Gitlab, Bitbucket, what have you. Works very well in practice. Bonus points if the tool can also tell you when you modified a function and didn't clean up the old findings in there. Then you can really enforce incremental improvement.
Disclaimer: I work on Teamscale (https://teamscale.com), which does all that.