https://issues.dlang.org/show_bug.cgi?id=24414

Alex Bryan <abryanbugzilla@proton.me> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |abryanbugzilla@proton.me

--- Comment #1 from Alex Bryan <abryanbugzilla@proton.me> ---
I've ran into this issue before and worked around it by putting this in a D file:

module util;
// for C files built with import C that try to use GCC/clang builtin that
importC does not provide

extern(C) int __builtin_clz(int v)
{
    return clz(v);
}

// count leading zeros.
int clz(uint v) pure nothrow @nogc @safe
in(v != 0)
{
    import core.bitop : bsr;
    return 31 - bsr(v);
}


and putting
__import util
at the top of the C file

--