Linking error

Processing uno (platform: atmelavr; board: uno; framework: arduino)

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Verbose mode can be enabled via `-v, --verbose` option
CONFIGURATION: https://docs.platformio.org/page/boards/atmelavr/uno.html
PLATFORM: Atmel AVR > Arduino Uno
HARDWARE: ATMEGA328P 16MHz 2KB RAM (31.50KB Flash)
Library Dependency Finder -> http://bit.ly/configure-pio-ldf
LDF MODES: FINDER(chain) COMPATIBILITY(soft)
Collected 5 compatible libraries
Scanning dependencies...
No dependencies
Linking .pioenvs/uno/firmware.elf
/tmp/ccznS5yl.ltrans0.ltrans.o: In function `main':
<artificial>:(.text.startup+0x8a): undefined reference to `StateController::setup()'
<artificial>:(.text.startup+0x92): undefined reference to `InputSignal::setup()'
<artificial>:(.text.startup+0x9a): undefined reference to `MorseInterpreter::setup()'
<artificial>:(.text.startup+0xa2): undefined reference to `OutputInterface::setup()'
<artificial>:(.text.startup+0xae): undefined reference to `StateController::loop()'
<artificial>:(.text.startup+0xb6): undefined reference to `InputSignal::loop()'
<artificial>:(.text.startup+0xbe): undefined reference to `MorseInterpreter::loop()'
<artificial>:(.text.startup+0xc6): undefined reference to `OutputInterface::loop()'
/tmp/ccznS5yl.ltrans0.ltrans.o: In function `_GLOBAL__sub_I_signalStorage':
<artificial>:(.text.startup+0xfc): undefined reference to `SignalStorage::SignalStorage()'
<artificial>:(.text.startup+0x138): undefined reference to `SimplePinInputSignal::SimplePinInputSignal(unsigned int, unsigned int, unsigned int,
 int, SignalStorage)'
<artificial>:(.text.startup+0x140): undefined reference to `vtable for InputSignal'
<artificial>:(.text.startup+0x142): undefined reference to `vtable for InputSignal'
<artificial>:(.text.startup+0x1ba): undefined reference to `MorseInterpreter::MorseInterpreter(float, InputSignal&, SignalStorage&)'
<artificial>:(.text.startup+0x1f0): undefined reference to `OutputInterface::OutputInterface(int, unsigned long, unsigned long, unsigned long, u
nsigned long, unsigned long)'
<artificial>:(.text.startup+0x204): undefined reference to `StateController::StateController(InputSignal&, OutputInterface&, MorseInterpreter&)'
collect2: error: ld returned 1 exit status
*** [.pioenvs/uno/firmware.elf] Error 1
========================================================================================================== [ERROR] Took 0.69 seconds ===========
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