/*
dmd -c -I./tango/core -I. -I./tango/core/vendor -m64 -version=WithDateTime -oftango-core-Variant-m64--version-WithDateTime.o ./tango/core/Variant.d
VARARG SET
./tango/core/Variant.d(770): Error: '__va_argsave_t' is not defined, perhaps you need to import std.c.stdarg; ?
./tango/core/Variant.d(770): Error: __va_argsave_t is used as a type
./tango/core/Variant.d(770): Error: variable tango.core.Variant.Variant.fromVararg.__va_argsave voids have no value
*/

    // Layout of this struct must match __gnuc_va_list for C ABI compatibility
    struct __va_list
    {
        uint offset_regs = 6 * 8;            // no regs
        uint offset_fpregs = 6 * 8 + 8 * 16; // no fp regs
        void* stack_args;
        void* reg_args;
    }

pragma(msg, "VARARG SET");

    struct __va_argsave_t
    {
        size_t[6] regs;   // RDI,RSI,RDX,RCX,R8,R9
        real[8] fpregs;   // XMM0..XMM7
        __va_list va;
    }