20. Default Function Arguments

Question.4

A developer puts default values in the .cpp definition instead of the .h declaration:

Header (driver.h):

void timer_start(int period_ms, int priority);

Source (driver.cpp):

void timer_start(int period_ms, int priority = 3) {
   // setup...
}

Another file calls timer_start(100);. What happens?

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Works — the compiler finds the default from the .cpp file
Compilation error in the calling file — it only sees the header, which has no default for priority
Works — but only with LTO (Link-Time Optimization) enabled
The default is ignored and priority gets a random value

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