Question

I have a program which does concatenation.

its like char *testConc(int a,..)
Where a indicates number of arguments are being passed for concatenation.
As legth keeps on changing is there is anything like constructor overloading in C

or any simple syntax which implements the functionality

Answer 1

C does not have function overloading capabilities. The syntax you have is called a variadic function, which can be used to perform what you asked.

The textConc function would look something like this:

char *textConc(int argc, ...)
{
    va_list args;
    char *str = NULL;
    size_t len = 0;

    va_start(args, argc);
    while (argc--)
    {
        /* next string */
        const char *temp = va_arg(args, const char *);
        size_t size = strlen(temp);
        /* make room and copy over */
        str = realloc(str, len+size+1);
        memcpy(str+len, temp, size+1);
        /* new length */
        len += size;
    }
    va_end(args);

    return str;
}

int main(int argc, char **argv)
{
    char *example = textConc(4, "Hello", "All", "good", "morning");
    puts(example);
    free(example);
    return 0;
}

If you use GCC, we can fake overloading completely, using a little help of macros.

Rename textConc to textConcN and use the following macros:

#define ARGCOUNT(...)  (sizeof((const char *[]){__VA_ARGS__})/sizeof(const char *))
#define textConc(...) textConcN(ARGCOUNT(__VA_ARGS__), __VA_ARGS__)


int main(int argc, char **argv)
{
    /* notice, no more need for the number of arguments */
    char *example =  textConc("Hello", "All", "good", "morning");
    puts(example);
    free(example);
    return 0;
}