[libcxx-commits] [libcxx] [libc++] Add a few _LIBCPP_ASSERT_INTERNALs to make sure internal invariants are kept (PR #114575)

[Louis Dionne via libcxx-commits]

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@@ -1990,10 +1998,12 @@ private:
   }
 
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pointer __get_long_pointer() _NOEXCEPT {
+    _LIBCPP_ASSERT_INTERNAL(__rep_.__l.__is_long_, "String has to be long when trying to get the long pointer");
     return _LIBCPP_ASAN_VOLATILE_WRAPPER(__rep_.__l.__data_);
   }
 
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 const_pointer __get_long_pointer() const _NOEXCEPT {
+    _LIBCPP_ASSERT_INTERNAL(__rep_.__l.__is_long_, "String has to be long when trying to get the long pointer");
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ldionne wrote:

You mean that after landing this patch, some internal tests unrelated to `string` (in particular, not libc++ tests) start breaking?

That's really strange, indeed there may be some subtle UB that the compiler is taking advantage of here.

https://github.com/llvm/llvm-project/pull/114575