Yes, you don't need C++ to get an inlined comparator, but C++ certainly makes it easier in the sense that you can get basically guaranteed inlining [1]. In the

Yes, you don't need C++ to get an inlined comparator, but C++ certainly makes it easier in the sense that you can get basically guaranteed inlining [1]. In the C case, your options are fewer, and often more reliant on optimization and the vagaries of the compiler. In particular, I tried to modify glibc's qsort to force inlining of the comparator, using both flatten and always_inline attributes, but failed probably because of the recursive nature of merge sort: the main sorting function is recursive, meaning it cannot be flattened without limit, which ends up inhibiting inlining of the comparator as well. It can definitely be made to work, but it's less automatic than C++ and compatators passed as template arguments. Of course, the "specialize everything" approach of C++ has plenty of downsides too! --- [1] Really, what you get is guaranteed specialization, and then inlining follows easily from that, if the compiler decides it is profitable to inline the small comparator into the sort function.