assignment makes integer from pointer without a cast [-Wint-conversion]

Question

i am new to c, i am trying to make a simple code in which i replace the vowels of an input with the * character... i am having trouble with the array (i am mainly familiar with python only using c now.)

#include <stdio.h>

 char* main() {
 int c;
 char* vowels[] = {'a', 'e', 'i', 'o', 'u'};

 while( 1 ) {   // means: true
  c = getchar();
  if(c == EOF) break;
  if(c = vowels) putchar('*'); 
  else putchar(c);
}
}

i keep receiving the same error message: novowels.c:5:41: note: (near initialization for ‘vowels[4]’) novowels.c:10:12: warning: assignment makes integer from pointer without a cast [-Wint-conversion] if(c = vowels) putchar('*'); ^

.... please help, i can't quite figure out how do complete this program of replacing vowels with *

And the Python tag just slipped in? Do not add unrealted tags! — too honest for this site
"// means: true" So why not use true and stdbool.h then? — too honest for this site
@Olaf Becausethat's C99 and OP may not have learned about C99 yet? There are thousands of reasons not to use the weird type _Bool. — fuz
@FUZxxl: true is an int, not _Bool. It is just standard C. And can you recify calling the unsigned integer type _Bool "weird"? — too honest for this site
@Olaf _Bool has different conversion rules from any other type. It also has a more restricted range than char which is something that breaks with the conventions of C (i.e. char being the most narrow type). — fuz

AnT AnT · Accepted Answer · 2016-02-17T23:20:46

Firstly, char *main() is illegal in C. It should be int main().

Secondly, 'a' and the like are integer constants in C. You cannot use them to initialize and array of char * elements. If you wanted a char array you should have declared it as

const char vowels[] = {'a', 'e', 'i', 'o', 'u'};

If you wanted a string array you should have declared it as

const char *const vowels[] = {"a", "e", "i", "o", "u"};

Finally, it is completely unclear what you were trying to say by c = vowels. If you want to check whether c is in vowels array, keep in mind that there's no core language feature that can do it for you (and certainly not the = operator). You have to implement the check manually or use an applicable library feature.

For example, one possible way to check it is

const char vowels[] = {'a', 'e', 'i', 'o', 'u'};
...
if (memchr(vowels, c, sizeof vowels) != NULL)
  putchar('*');

Alternatively, it can be expressed as

const char *const vowels = "aeiou";
...
if (strchr(vowels, c) != NULL)
  putchar('*');

assignment makes integer from pointer without a cast [-Wint-conversion]

3 Answers