Redefinition of main

Question

I started writing code in C, and I needed the toupper function in my code, so I added to ctype.h header file to include it.

All of a sudden I can't run my program because I keep getting a redefinition of main error from my compiler.

Before I added the header ctype.h, and even if I get rid of the header file ctype.h, the program runs. What do I do to fix this?

#include <stdio.h>
#include <ctype.h>

#define NAMESPACE 20

int main (void)
{  

    char first_name[NAMESPACE], middle_name[NAMESPACE], last_name[NAMESPACE];
    printf ("Please enter your first, middle and last name.\n");
    scanf ("%s", first_name);
    scanf("%s", middle_name);
    scanf ("%s", last_name);
    printf ("%s %0.1s %s", first_name, middle_name, last_name);
    return 0;
}

---

[error] redefinition of "int main()":

Here is the code saved as a header file called ctype.h in my DEV c++ ,

#include<stdio.h>
#include<conio.h>
int main (void)
{
char ch[]="I AM AN IDIOT.";
char c='A';
int i=0;
while(c)
{
c=getch();
printf("%c\a",ch[i]);
i++;
if(i==14)
{
printf(" "); i=0;
}
}
}

Solution

The code you posted does not explain the error message you presented. It has some issues, but none that should elicit any error. There are several possible reasons for the error, among them:

1. My best guess would be that you have another source file in the project that has its own main() function, and the IDE is configured to include both in the same target program. That might result simply by virtue of them being collocated in the same directory. That other source file might even be something dumb, such as a backup copy of the file you presented.
2. Alternatively, it may be that you have a project-local header named ctype.h, which defines a main() function, and Dev C++ is choosing that one instead of the standard library's header. (Yes, this is really just a variant on (1); there's not much leeway in "redefinition of 'int main()'".)
3. Or perhaps Dev C++ misspoke, and it's complaining about a redeclaration of main() rather than a redefinition. If its ctype.h header contained a conflicting declaration, such as int main(int argc, char *argv[]), then it might issue a complaint. In that unlikely case, you might be able to resolve the error by changing the declaration of your main() to the two-argument form.

Comments

[R Sahu]

The code looks OK to me. What's your platform?

[Michael Dorgan]

Any chance you are accidently linkin in 2 different projects that you created?

[Michael Dorgan]

NAMESPACE as a constant also scares me, though it should be fine.

[Keith Thompson]

Is that the entire error message? Does it refer to a line number? To a file?

[rfreytag]

can you post a screenshot of your project in dev+c++?

[ncu]

Yes you were right on number 2. When i clicked the error message, a program that i've never seen before came up, and it was named ctype.h, and saved as a header file. It had a main function in it as well. How do I get the standard ctype.h file header back?

[John Bollinger]

If you are sure that the ctype.h you found isn't Dev C++'s version of the standard library header, and especially if it's in one of your project directories rather than somewhere in one of Dev C++'s system directories, then you can probably just delete it. If a rogue file has actually replaced one of Dev C++'s standard headers, then I would completely wipe Dev C++ from the system, and install a fresh copy from a trusted source.

[user3629249]

suggestion '3' will raise two warnings about unused parameters, unless the code is drastically changed to use those two parameters.

[John Bollinger]

@user3629249, indeed, yes, adding the argc and argv parameters would likely cause the compiler to raise warnings. So? If the problem had been that there was a conflicting declaration of main() in one of the standard headers, then there would not have been a good alternative. It's important to understand what a warning is telling you, but certain warnings simply need to be ignored or suppressed.