c - How to use iconv for utf8 conversion? -

i want convert data in other encodings utf-8. i'm stranded following problems:

1. executing attached code gives me: pointer being freed not allocated in iconv(). why iconv play memory?
2. when don't free(dst) doesn't crash nothing printed. not gibberish. what's wrong?

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void utf8(char **dst, char **src, const char *enc) {     iconv_t cd;     size_t len_src,            len_dst;      len_src = strlen(*src);     len_dst = len_src * 8; // enough ascii utf8?      cd = iconv_open("utf-8", enc);      *dst = (char *)calloc(len_dst+1, 1);      iconv(cd, src, &len_src, dst, &len_dst);     iconv_close(cd); }  int main(int argc, char **argv) {     char *src = "hello world";     char *dst;      utf8(&dst, &src, "ascii");     printf("%s\n", dst);      free(dst);     return 0; } 

quote iconv() description @ posix.1-2008

size_t iconv(iconv_t cd, char **restrict inbuf,        size_t *restrict inbytesleft, char **restrict outbuf,        size_t *restrict outbytesleft); 

the variable pointed outbuf shall updated point byte following last byte of converted output data.

you need save , restore *dst (and possibly *src) inside utf8() function.