> So in C typically you'd have a runtime generic routine that doesn't inline.

With LTO you get many of the same advantages as C++ template code, there's nothing magic about C++ template optimizations, it's all about whether the compiler can see all function bodies in a call hierarchy.

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simonask an hour ago | parent [-]

LTO cannot change the layout of structs. For something like a hash map implementation, it matters whether inner nodes store a pointer to the key and value, or whether it stores a pointer to each. To achieve this in C, you have no other options than emulating templates using macros.

	▲	flohofwoe 41 minutes ago \| parent [-]
		The question is whether a hash-map implementation that works on a general `[key, index]` item and where index references at separate array of values isn't actually better for some access patterns ;) And of course the other alternative to macros is code-generation (but macros are actually often fine). But this also only matters for actually reusable generic code. If I'd implement a super-hot-path hashmap in C, I would stamp out a specialized version by hand instead of relying on a generic implementation. But for 90% of cases, a solution like in stb_ds.h is probably good enough.