GCC can also use UBSan (and ASan) [1], and furthermore, it shouldn't be "several...

GCC can also use UBSan (and ASan) [1], and furthermore, it shouldn't be "several times slower" (are you thinking of Valgrind?). Clang itself describes the checks as "small runtime cost" [2] and there's a minimal variant as well.

[1]: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.h... [2]: https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html