c - Arduinoのcore.a(main.cpp.o)エラーとは?

Question

Arduino でコードをコンパイルしていたところ、突然次のエラーが発生しました。

 core.a(main.cpp.o): In function `main':
 D:\Personal\Arduino\arduino-1.0.4-windows\arduino-  1.0.4\hardware\arduino\cores\arduino/main.cpp:11: undefined reference to `setup'
 D:\Personal\Arduino\arduino-1.0.4-windows\arduino-1.0.4\hardware\arduino\cores\arduino/main.cpp:14: undefined reference to `loop'

それが何を意味するのかわかりません。これが私のコードです：

#ifndef dht_h
#define dht_h

#if ARDUINO < 100
    #include <WProgram.h>
#else
    #include <Arduino.h>
#endif

#define DHT_LIB_VERSION "0.1.05"

#define DHTLIB_OK                0
#define DHTLIB_ERROR_CHECKSUM   -1
#define DHTLIB_ERROR_TIMEOUT    -2
#define DHTLIB_INVALID_VALUE  -999
#include <dht.h>

#define TIMEOUT 10000

class dht
{
    public:
        int read22(uint8_t pin);
            double humidity;
            double temperature;

    private:
        uint8_t bits[5];  // Buffer to receive data
        int read(uint8_t pin);
};
#endif


// return values:
// DHTLIB_OK
// DHTLIB_ERROR_CHECKSUM
// DHTLIB_ERROR_TIMEOUT
int dht::read22(uint8_t pin)
{
    // READ VALUES
    int rv = read(pin);
    if (rv != DHTLIB_OK)
    {
        humidity    = DHTLIB_INVALID_VALUE;  // Invalid value, or is NaN prefered?
        temperature = DHTLIB_INVALID_VALUE;  // Invalid value
        return rv;
    }

    // CONVERT AND STORE
    humidity    = word(bits[0], bits[1]) * 0.1;

    if (bits[2] & 0x80) // negative temperature
    {
        temperature = word(bits[2]&0x7F, bits[3]) * 0.1;
        temperature *= -1.0;
    }
    else
    {
        temperature = word(bits[2], bits[3]) * 0.1;
    }

    // TEST CHECKSUM
    uint8_t sum = bits[0] + bits[1] + bits[2] + bits[3];
    if (bits[4] != sum) return DHTLIB_ERROR_CHECKSUM;

    return DHTLIB_OK;
}

//Private
// return values:
// DHTLIB_OK
// DHTLIB_ERROR_TIMEOUT
int dht::read(uint8_t pin)
{
    // INIT BUFFERVAR TO RECEIVE DATA
    uint8_t cnt = 7;
    uint8_t idx = 0;

    // EMPTY BUFFER
    for (int i=0; i< 5; i++) bits[i] = 0;

    // REQUEST SAMPLE
    pinMode(pin, OUTPUT);
    digitalWrite(pin, LOW);
    delay(20);
    digitalWrite(pin, HIGH);
    delayMicroseconds(40);
    pinMode(pin, INPUT);

    // GET ACKNOWLEDGE or TIMEOUT
    unsigned int loopCnt = TIMEOUT;
    while(digitalRead(pin) == LOW)
            if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;

    loopCnt = TIMEOUT;
    while(digitalRead(pin) == HIGH)
            if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;

    // READ THE OUTPUT - 40 BITS => 5 BYTES
    for (int i=0; i<40; i++)
    {
        loopCnt = TIMEOUT;
        while(digitalRead(pin) == LOW)
            if (loopCnt-- == 0)
                return DHTLIB_ERROR_TIMEOUT;

        unsigned long t = micros();

        loopCnt = TIMEOUT;
        while(digitalRead(pin) == HIGH)
            if (loopCnt-- == 0)
                return DHTLIB_ERROR_TIMEOUT;

        if ((micros() - t) > 40)
            bits[idx] |= (1 << cnt);
        if (cnt == 0) // Next byte?
        {
            cnt = 7;
            idx++;
        }
        else
            cnt--;
    }
    return DHTLIB_OK;
}

このコードを修正するにはどうすればよいですか?