CODEWITHSUNDEEP
cfunction-declaration
Psi
Psi

Reputation: 280

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

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

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).

Upvotes: 2

Views: 739

Answers (2)

Jonathan Leffler
Jonathan Leffler

Reputation: 753695

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.

Upvotes: 6

Ed Heal
Ed Heal

Reputation: 59997

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

Upvotes: 3

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