C Programming - Const - Discussion

/*Actually the code will work fine if we declare the pointer in main function as*/

const char *ptr=fun();

/*It is because here the function returns a constant character pointer value. so it should be received like that only*/

return "hello";

/*This statement will store the string in memory and will return the base address of the string. It will work fine since the function is declared as a function which will return a constant character pointer value and it is received by a constant character pointer in main function.*/

@Kiran :

Here we declare the function as well as we call also in the statement
char *ptr=fun();
you can justify it by following ex:

#include<stdio.h>
const char *fun();
int main()
{
char *ptr = fun();
return 0;
}
const char *fun()
{
printf("must be call");
return "Hello";
}

Some of the compilers give error: invalid conversion from 'const char*' to 'char*' but some give the output successfully..

I hope there is no problem with assigning char* to const char*. So no error.

As there is printf statement in the program there is no output.
So option C is correct.

\\Check with the following program. It will help you friends.

#include<stdio.h>
const char *fun();
int main()
{
char *ptr = fun();
int i;
for(i=0;i<5;i++)
{
printf("%c",*(ptr+i));
}
return 0;
}
const char *fun()
{
return "Hello";
}

Here we have function and pointer declaration only. No calling.

Try this one, you guys may understand.

#include<stdio.h>
const char *fun()
{
return "Hello";
}
int main()
{
char *ptr=fun();
printf("%c",*ptr++);

printf("%c", *ptr++);
printf("%c", *ptr++);
printf("%c", *ptr++);
printf("%c", *ptr++);

getch();
}

@Arun prasad:

O/P in gcc compiler is also b its is throwing error i.e invalid conversion from const char to char. here is the code and output:

#include<stdio.h>
const char *fun();

int main()
{
char *ptr =fun();
return 0;
}
const char *fun()
{
return "Hello";
}

o/p:7 INDIABIXTEST6_18.C [Error] invalid conversion from 'const char*' to 'char*' [-fpermissive]

@All. Refer this code.

#include<stdio.h>
const char *fun();

int main()
{
char *ptr = (char*)fun();
//printf("%p %s\n",&ptr,ptr);
puts(ptr);
return 0;
}
const char *fun()
{
return "Hello";
}

The correct o/p is B in TC++ compiler.

Error: Cannot convert from 'const char *' to 'char *'. This occurs because fun() returns a pointer to a constant character which is being assigned to a pointer to a non-constant character.

Yes, you are right @Lakshmi.

Because pointer contains constant string only.

So, the fun() returns a constant string so to store constant string pointer must be required.

Thank you.

If the const weren't there then the ans will be C otherwise it gives error i.e ans will be B in case of Turbo C/C++ compiler.

Here the string "hello" is local to that function and when it returns it goes out of scope and returns nothing.