copy char array to char* in C

Question

I have a char array that I need to define in a function and return a char pointer, so i defined MAX which is the biggest size my char array can be according to my assigment and after I append part of it I want to copy it to char pointer so I can return it. the size of the part of the array that is full is i and I did malloc to with this size, then I did memcpy to copy only the part I want(strcpy copied also the ampty fields), but it still put in my result more weird stuff, how do I get rid of this?

Code:

char* result = (char*)malloc(i*sizeof(char));

if (result == NULL)
    free(result);

memcpy(result, temp, i);

printf("%s", result);
return result;

Result of printf:

ccbcc²²²²U┤

while the result should be only "ccbcc".

If i is strlen(temp) then you allocate one too little (for the terminating null) and you copy one too little (that terminating null). — Paul Ogilvie
– Paul Ogilvie, Commented Dec 24, 2019 at 15:21
temp's size is 3000 but only i-1 fileds have values. the strlen comment return me 3000 and I dont want that.. — user12591754
– user12591754, Commented Dec 24, 2019 at 15:27
If temp is a string, use strcpy(result, temp) instead of memcpy and make sure i > strlen(temp). Also, do not cast the pointer returned by malloc in C programs. — Lxer Lx
– Lxer Lx, Commented Dec 24, 2019 at 15:37
if (result == NULL) free(result); FYI: free(NULL) is a no-op, maybe better: if (result == NULL) { fprintf(stderr, "malloc error\n"); exit(EXIT_FAILURE); } — pmg
– pmg, Commented Dec 24, 2019 at 15:50
char* result = (char*)malloc(i*sizeof(char)); allocates 1-byte of memory. The only string you can store there is the empty-string (single '\0' char -- not very useful) — David C. Rankin
– David C. Rankin, Commented Dec 24, 2019 at 16:17

Himanshu Singh · Accepted Answer · 2019-12-24 15:26:30Z

1

Instead of printing like this: printf("%s", result);

you should be printing only indexes which are initialized and contains value:

for(int k=0;k<i;k++){
  printf("%c", s[k]);
}

answered Dec 24, 2019 at 15:26

Himanshu Singh

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2 Comments

user12591754 Over a year ago

I tried this one at the begining and it didnt work, but now suddenly it works! thanks:)

Himanshu Singh Over a year ago

@Ran121 great !

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