Question

I need to pass a char * to a function, but this function really needs const?

But I’m reading it from file and it’s dynamic for me:

fseek(fcode, 0, SEEK_END);
i=ftell(fcode);
square_scm = (char*) malloc(i);
//free(square_scm);
fseek(fcode, 0, SEEK_SET);
fread(square_scm, 1, i, fcode);
scheme_load_string(sc, square_scm);

So square_scm here is:

"(display 
    (string-append "Answer: " 
    (number->string (square 6.480740698407859)) "\n"))юоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюоюо"

without free :

"(display 
    (string-append "Answer: " 
    (number->string (square 6.480740698407859)) "\n"))ННээээ««««««««««««««««ю"

How can I make it like char[size], like:

"(display 
    (string-append "Answer: " 
    (number->string (square 6.480740698407859)) "\n"))"

?

Answer 1

Don’t free the malloced memory until you are done with it. And to answer your question, always leave space for the terminating null byte in the strings and do set the last byte to null byte.

fseek(fcode, 0, SEEK_END);
i=ftell(fcode);

//allocate for null byte too
square_scm = malloc(i + 1);

//reset the memory before using it
memset(square_scm, 0, i + 1);

fseek(fcode, 0, SEEK_SET);
fread(square_scm, 1, i, fcode);
square_scm[i] = 0; //not really required as we have already memset it
scheme_load_string(sc, square_scm);

//now you should free it, assuming it is not used anymore
free(square_scm);