[libcxx-commits] [libcxx] [libc++] Make `<set>` `std::multiset` constexpr as part of P3372R3 (PR #206257)

[A. Jiang via libcxx-commits]

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@@ -9,18 +9,19 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
 // Some fields in the test case variables are deliberately not explicitly initialized, this silences a warning on GCC.
 // ADDITIONAL_COMPILE_FLAGS(gcc-style-warnings): -Wno-missing-field-initializers
+// ADDITIONAL_COMPILE_FLAGS(has-fconstexpr-steps): -fconstexpr-steps=2147483647
----------------
frederick-vs-ja wrote:

LGTM with nits. "Critical" tests seem all passed, and the failures with LLVM-libc build are unrelated.

2147483647 looks a bit scary to me as it permits extremely long compile time. I roughly verified this on Godbolt and found that 4000000 should be sufficient. (The exact number seems slightly less than 3400000.) Or maybe we can use GCC's default limit which is 33554432.

```suggestion
// ADDITIONAL_COMPILE_FLAGS(has-fconstexpr-steps): -fconstexpr-steps=4000000
```

https://github.com/llvm/llvm-project/pull/206257