100. Constructors-II

Question.3

A developer uses one constructor to call another:

class SPI {
   int speed;
   int mode;
public:
   SPI(int s, int m) : speed(s), mode(m) { init_hw(); }
   SPI(int s) : SPI(s, 0) {}  // Delegates to 2-arg version
   SPI() : SPI(1000000) {}     // Delegates to 1-arg version
};

What does SPI() do?

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Nothing -- default constructor is empty
Calls SPI(1000000), which calls SPI(1000000, 0), which initializes speed=1000000, mode=0 and calls init_hw()
Compilation error -- constructors cannot call other constructors
Creates an uninitialized SPI object

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