/tmp/ccmYmFac.o: In function `WeekdayOfTheFirstDay(int, int)':
foo.cc:(.text+0x26): undefined reference to `DaysOfYear(int)'
foo.cc:(.text+0x49): undefined reference to `DaysOfMonth(int, int)'
/tmp/ccmYmFac.o: In function `PrintfMonth(int, int)':
foo.cc:(.text+0x1d5): undefined reference to `DaysOfMonth(int, int)'
/tmp/ccmYmFac.o: In function `main':
foo.cc:(.text.startup+0x3a): undefined reference to `PrintMonth(int, int)'
collect2: error: ld returned 1 exit status
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