/Zc:externC- compiler flag in vs 2022

Question

Hi I am trying to convert an old project from vc++2013 to vc++ 2022. I am getting a lot of C2733 Errors. Most of them are related to overrides of memory allocation functions. Here's one example

extern "C"
{
    void* _calloc_base( size_t nSize )
    {
        return nullptr;
    }
}

Based on my searching and reading https://learn.microsoft.com/en-us/cpp/build/reference/zc-externc?view=msvc-170 I am supposed to add /Zc:externC- to compiler options. But for some reason its not working for me.

compiler flags

I made a simple 1 file test project to replicate this. (Its not working even in my test proj) https://www.dropbox.com/scl/fi/g36wfk3xkt8jls0nbhqsv/externCTest.zip?rlkey=kaf0c3k2eln7ndlcytyhsswhy&dl=0