whats the meaning of this error?

In file included from D:\Arduino\libraries\SPI\/SPI.h:15,
from D:\Arduino\libraries\SPI\SPI.cpp:12:
D:\Arduino\hardware\Sanguino\cores\arduino/pins_arduino.h:72: error: previous declaration of 'const uint16_t port_to_mode_PGM []' with 'C++' linkage
D:\Arduino\hardware\Sanguino\cores\arduino/Arduino.h:127: error: conflicts with new declaration with 'C' linkage
D:\Arduino\hardware\Sanguino\cores\arduino/pins_arduino.h:73: error: previous declaration of 'const uint16_t port_to_input_PGM []' with 'C++' linkage
D:\Arduino\hardware\Sanguino\cores\arduino/Arduino.h:128: error: conflicts with new declaration with 'C' linkage
D:\Arduino\hardware\Sanguino\cores\arduino/pins_arduino.h:74: error: previous declaration of 'const uint16_t port_to_output_PGM []' with 'C++' linkage
D:\Arduino\hardware\Sanguino\cores\arduino/Arduino.h:129: error: conflicts with new declaration with 'C' linkage
D:\Arduino\hardware\Sanguino\cores\arduino/pins_arduino.h:76: error: previous declaration of 'const uint8_t digital_pin_to_port_PGM []' with 'C++' linkage
D:\Arduino\hardware\Sanguino\cores\arduino/Arduino.h:131: error: conflicts with new declaration with 'C' linkage
D:\Arduino\hardware\Sanguino\cores\arduino/pins_arduino.h:78: error: previous declaration of 'const uint8_t digital_pin_to_bit_mask_PGM []' with 'C++' linkage
D:\Arduino\hardware\Sanguino\cores\arduino/Arduino.h:133: error: conflicts with new declaration with 'C' linkage
D:\Arduino\hardware\Sanguino\cores\arduino/pins_arduino.h:79: error: previous declaration of 'const uint8_t digital_pin_to_timer_PGM []' with 'C++' linkage
D:\Arduino\hardware\Sanguino\cores\arduino/Arduino.h:134: error: conflicts with new declaration with 'C' linkage


happened when i tried to compile

I would guess you are declaring values twice. Perhaps you un-commented two different LCD displays by accident and need to double check your config.h file.