isValidMemory

pub fn isValidMemory(address: usize) bool {
    // We are unable to determine validity of memory for freestanding targets
    if (native_os == .freestanding or native_os == .other or native_os == .uefi) return true;

    const page_size = std.heap.pageSize();
    const aligned_address = address & ~(page_size - 1);
    if (aligned_address == 0) return false;
    const aligned_memory = @as([*]align(page_size_min) u8, @ptrFromInt(aligned_address))[0..page_size];

    if (native_os == .windows) {
        const windows = std.os.windows;

        var memory_info: windows.MEMORY_BASIC_INFORMATION = undefined;

        // The only error this function can throw is ERROR_INVALID_PARAMETER.
        // supply an address that invalid i'll be thrown.
        const rc = windows.VirtualQuery(@ptrCast(aligned_memory), &memory_info, aligned_memory.len) catch {
            return false;
        };

        // Result code has to be bigger than zero (number of bytes written)
        if (rc == 0) {
            return false;
        }

        // Free pages cannot be read, they are unmapped
        if (memory_info.State == windows.MEM_FREE) {
            return false;
        }

        return true;
    } else if (have_msync) {
        posix.msync(aligned_memory, posix.MSF.ASYNC) catch |err| {
            switch (err) {
                error.UnmappedMemory => return false,
                else => unreachable,
            }
        };

        return true;
    } else {
        // We are unable to determine validity of memory on this target.
        return true;
    }
}