Is the 'main' function classified as a function definition in C?

Question

The reason I am asking is I have been presented with a piece of code and when explaining the difference between the function declarations at the top of the code and the function definitions at the bottom, I was asked if the 'main' function is also considered a function definition or if it is considered as something else (as main functions are essential unlike other functions).

score 6 · Accepted Answer · edited May 23 '17 at 12:13

In a hosted implementation of C (the normal sort), the only novel features of main() compared to any other function are:

It is where the program execution starts.
It does not have to be pre-declared.
If execution reaches the } at the end, it behaves as if there was a return 0; before the }^*.

In all other respects, main() is a normal function. It can be called recursively in C (whereas a C++ program cannot call its main() recursively).

Since a function is defined when its body is specified, when you write int main(void) { … } or int main(int argc, char **argv) { … } or any alternative, you are defining the function because the braces are present so the function body is defined.

^* ^{See What should main() return in C and C++ for some minor caveats about the return 0; statement if the return type is not compatible with int.}

score 3 · Answer 2 · answered Jan 09 '17 at 23:45

3

Main is a function like all the rest. Just has a different semantics and different requirements.

The semantics being it is the start of the program.

The requirements it has a predefined set of signatures

answered Jan 09 '17 at 23:45

Ed Heal

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You misunderstood. I am not asking if it is a function, I am asking if the 'main' code can be considered as a function definition. – Psi Jan 09 '17 at 23:46
_I was asked if the 'main' function is also considered a function definition or if it is considered as something else_ - I answered this bit – Ed Heal Jan 09 '17 at 23:48
You still do not quite follow. I must have phrased it badly. See Jonathan Leffler's post for the answer I was looking for – Psi Jan 09 '17 at 23:59
@ThomasHollis-- "Main is a function like all the rest." I believe that the point was that a function is defined when its body is specified, and `main()` is no different in this respect. This answers the question, albeit in a slightly laconic manner. – ad absurdum Jan 10 '17 at 00:18
It was rather a bit to the point. Thanks for the expansion of the meaning of the statement – Ed Heal Jan 10 '17 at 00:21

Is the 'main' function classified as a function definition in C?

2 Answers2