Why not void main() in C?

Question

2.56/5 (5 votes)

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Hi expert, My c code is here:

C++

#include<stdio.h>
void main(){

printf("Hello world");


}

The codeblock shows the error:

||warning: command line option '-Wzero-as-null-pointer-constant' is valid for C++/ObjC++ but not for C [enabled by default]|
C:\Users\Amir Khasru\Desktop\pointers.c|2|error: return type of 'main' is not 'int' [-Wmain]|
||=== Build failed: 1 error(s), 1 warning(s) (0 minute(s), 0 second(s)) ===|

What I have tried:

I tried to compile the above code through codeblock though never succeed. Please explain this?

Posted 12-Mar-16 7:49am

Member 12378355we

Updated 19-Jan-22 21:39pm

PIEBALDconsult

v10

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Comments

PIEBALDconsult 12-Mar-16 13:57pm

What compiler? What error do you get?
Please use Improve question to add context and detail.

Member 12378355we 12-Mar-16 14:11pm

Code block!! I updated!

PIEBALDconsult 12-Mar-16 14:23pm

OK, so it looks like it's a non-conforming compiler, how odd. Change the return type to int or use a better compiler.

Member 12378355we 12-Mar-16 15:24pm

Thanks

Member 12378355we 12-Mar-16 15:40pm

So we could even return char,float,double, pointer type data from main()....:))

PIEBALDconsult 12-Mar-16 17:47pm

No. Int or nothing.

[no name] 12-Mar-16 14:31pm

No Need to give a '1' for the question. Does the voter remember the time he/she started programming?
My small 5 to correct this a Little bit.

Member 12378355we 12-Mar-16 15:26pm

I've just started my coding, you know. Thanks.

2 solutions

Solution 2

Because main have to return an int.
See ISO/IEC 9899 (C99) and ISO/IEC 9899:201x (C11) at §5.1.2.2.1 Program startup:

Quote:

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.

You can define main with the 2 parameters int argc and char *argv[], or nothing. But the returns, as per all current standards, cannot be void.
Anyway some compilers allow the form void main(void) { /* ... */ } as private extension not standard compliant.

Posted 13-Mar-16 6:56am

Frankie-C

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Patrice T · Accepted Answer · 2016-03-12T10:16:00

Solution 1

From a C language point of view, this code is perfectly legal.

C++

#include<stdio.h>
void main(){
    printf("Hello world");
}

So the only possibility is that the compiler do not conform to C language or do not run in C mode. As PIEBALDconsult said, "It is compiler dependent".

Posted 12-Mar-16 10:16am

Patrice T

Updated 12-Mar-16 11:48am

v3

Comments

Member 12378355we 13-Mar-16 6:55am

Could char/float/double/* main() be possible?

PIEBALDconsult 13-Mar-16 13:22pm

No.

manoranjan 14-Mar-16 3:37am

This is not the right answer. main() function returns int (and not void). See Solution 2.