CODEWITHSUNDEEP
cstandardslanguage-lawyerc11
this
this

Reputation: 5290

Is this a valid definition for main()

The C11 Standard declares that:

5.1.2.2.1 Program startup

  1. The function called at program startup is named main. The implementation declares no prototype for this function. It shall be defined with a return type of int and with no parameters:

    int main(void) { /* ... */ }

    or with two parameters (referred to here as argc and argv, though any names may be used, as they are local to the function in which they are declared):

    int main(int argc, char *argv[]) { /* ... */ }

    or equivalent; 10), or in some other implementation-defined manner.

10) Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as char ** argv, and so on.

We will ignore this part: or in some other implementation-defined manner. since I'm interested only in definitions equivalent to the two above examples.

Would this be a valid definition for main since char* a[4] and char** are equivalent:

int main(int argc, char* argv[4]){/*...*/}

How about a VLA array, we are assuming printf will return a positive int value:

int main(int argc, char* argv[printf("Hello there!")]){/*...*/}

Upvotes: 8

Views: 238

Answers (2)

haccks
haccks

Reputation: 106092

int main(int argc, char* argv[4]){/*...*/}

is a valid signature of main. Compiler will ignore 4 in char argv[4] and it is equivalent to char argv[] = char **argv. Same goes with second signature.

Upvotes: 2

Jens Gustedt
Jens Gustedt

Reputation: 78943

Yes, this is all covered by the "or equivalent". The footnote about renaming parameters or using typedefed types are just examples.

My favorite variant is

int main(int argc, char* argv[argc+1]){/*...*/}

because it has the most information about the semantic of all main functions.

Upvotes: 5

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