It depends upon the platform, the language and the toolsets. For instance, for C, a trick I've used is to (if I can) use different C compilers and crank the warnings/errors to 11 and fix every complaint (or try to---it can be daunting to attempt this all at once).
Other tricks---run the code through linters or other stylistic nit-pickers and fix those too. I haven't yet used a code reformatter, but that's a quick way to get code into a consistent style.
I'm all in C, too: kernel drivers from wifi chipset vendors. There's one C compiler we can use (gcc) and we're even restricted to working with a specific version (because cross compiling). We have to be very careful about changing any of the code because we have to integrate any changes into the next drop of the vendors' code. Static analysis is our best bet. Is a really interesting problem.
Other tricks---run the code through linters or other stylistic nit-pickers and fix those too. I haven't yet used a code reformatter, but that's a quick way to get code into a consistent style.