Discussion
If the different command line arguments are supplied at different times would the output of the following program change?
#include <stdio.h>
int main(int argc, char **argv)
{
printf("%d\n", argv[argc]);
return 0;
}
Answer: B
Correct answer: No
argv[argc] is guaranteed by the standard to be a null pointer, marking the end of the vector. That is true whatever arguments are supplied, so the value printed never changes.
Note the further problem: the format is %d while the argument is a pointer, which is itself undefined behaviour and typically prints 0. The question turns on the guarantee at the end of the array - a program can therefore walk argv until it meets the null pointer without consulting argc at all.
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