[libcxx-commits] [libcxx] [libc++] `std::ranges::advance`: avoid unneeded bounds checks when advancing iterator (PR #84126)

[Jan Kokemüller via libcxx-commits]

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@@ -42,6 +42,18 @@ constexpr void check_forward(int* first, int* last, std::iter_difference_t<It> n
     // regardless of the iterator category.
     assert(it.stride_count() == M);
     assert(it.stride_displacement() == M);
+    if (n == 0) {
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jiixyj wrote:

I think I finally understand. I now pass in the expected `stride_count`/`stride_displacement`/`equals_count` as appropriate so that the logic of the tests is now simpler. The tradeoff is at the call site of `check_forward`/`check_backward` where I need to calculate the expected values.

Did you have something like this in mind?

https://github.com/llvm/llvm-project/pull/84126