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But why is C++ refusing to add "restrict" to its spec? C has restrict in its spec, C++ has not. Of course compilers inherit restrict from C, but it's not super

• Galanwe 3y ago
  In or out of the spec doesn't really matter. You can use __restrict__ in C++ and any compiler will diligently accept it, if not for the occasional warning. The larger issue is that C and C++ have convoluted aliasing rules which makes reasoning and flagging non-aliased regions hard. The most innocent of cast can break strict aliasing rules and send you in horrible debugging scenarios. The sad side effect being people adding -fno-strict-aliasing to -O2/3.
• WanderPanda 3y ago
  I was wondering the same! I just recently came across the restrict keyword (thanks to someone mentioning it on HN) but I have never seen it being mentioned before, even though I was looking into all sorts of optimizations (also ChatGPT would never bring it up on its own). Since with templating everything seems to be going header only anyways, I feel like we should give the compiler more power to reason about the memory layout, even through multiple levels of function invocation/inlining. I wrote some library where basically all shapes can be infered at compile-time (through templates) but the compiler only rarely seems to take advantage of this.