C++ and AVR - http://xqms.github.com/blog/cpp_and_avr.html

avr_gcc.sh

avr-g++ -mmcu=atmega32 -fno-exceptions -fno-rtti -O2 -o file.elf file.cpp

c_spi_bitbang.cpp

void spi_bb_init(void)
{
	/* Drive CS high (inactive) */
	SPI_BB_CS_PORT |= (1 << SPI_BB_CS_NUM);
	SPI_BB_CLOCK_PORT &= ~(1 << SPI_BB_CLOCK_NUM);

	/* Set pins as output */
	SPI_BB_CS_DDR |= (1 << SPI_BB_CS_NUM);
	SPI_BB_DATA_DDR |= (1 << SPI_BB_DATA_NUM);
	SPI_BB_CLOCK_DDR |= (1 << SPI_BB_CLOCK_DDR);
}

void spi_bb_write(uint8_t value)
{
	uint8_t i;

	SPI_BB_CS_PORT &= ~(1 << SPI_BB_CS_NUM);

	for(i = 0; i < 8; ++i)
	{
		if(value & (1 << i))
			SPI_BB_DATA_PORT |= (1 << SPI_BB_DATA_NUM);
		else
			SPI_BB_DATA_PORT &= ~(1 << SPI_BB_DATA_NUM);

		/* Well, we would need delays or something here, but just
		   pretend our slave can deal with our fast irregular output */
		SPI_BB_CLOCK_PORT |= (1 << SPI_BB_CLOCK_NUM);
		SPI_BB_CLOCK_PORT &= ~(1 << SPI_BB_CLOCK_NUM);
	}

	SPI_BB_CS_PORT |= (1 << SPI_BB_CS_NUM);
}

c_spi_bitbang.h

#define SPI_BB_CLOCK_PORT PORTA
#define SPI_BB_CLOCK_DDR DDRA
#define SPI_BB_CLOCK_NUM 4

#define SPI_BB_DATA_PORT PORTA
#define SPI_BB_DATA_DDR DDRA
#define SPI_BB_DATA_NUM 5

#define SPI_BB_CS_PORT PORTA
#define SPI_BB_CS_DDR DDRA
#define SPI_BB_CS_NUM 6

void spi_bb_init(void);
void spi_bb_write(uint8_t value);

cpp_spi_bitbang.h

#include <avrlib/portdef.h>

template<class ClockPin, class DataPin, class CSPin>
class SPIBitBang
{
public:
	static void init()
	{
		CSPin(1); // Drive high (inactive)
		ClockPin(0);

		avr::setOutput()
			<< ClockPin()
			<< DataPin()
			<< CSPin()
		;
	}

	static void write(uint8_t value)
	{
		CSPin(0);

		for(uint8_t i = 0; i < 8; ++i)
		{
			DataPin(value & (1 << i));
			ClockPin(1);
			ClockPin(0);
		}

		CSPin(1);
	}
};

cpp_your_code.cpp

#include "cpp_spi_bitbang.h"

namespace pins
{
	using namespace avr;

	typedef Pin<PortA, 4> Clock;
	typedef Pin<PortA, 5> Data;
	typedef Pin<PortA, 6> CS;
}

typedef SPIBitBang<pins::Clock, pins::Data, pins::CS> SPI;

int main()
{
	SPI::init();
	SPI::write(0xFF);
}

output.asm

  6c:   sbi     0x1b, 6 ; 27
  6e:   cbi     0x1b, 4 ; 27
  70:   in      r24, 0x1a       ; 26
  72:   ori     r24, 0x70       ; 112
  74:   out     0x1a, r24       ; 26