CODEWITHSUNDEEP
carraysstringfunctionpointers
Eddie Romanenco
Eddie Romanenco

Reputation: 321

C using a pointer to a string in a function

a quick question. I'm trying to write a function which recieves a name of a string and prints its second character, But it won't compile (on http://ideone.com), can you address the issue? I don't see the problem as I am sending an address into the function, and asking to access the character in that address.

#include <stdio.h>

int main(void) {
    char line[4] = "abc";
    test(line);
    return 0;
}

void test(int point) {
    point++;
    printf("%c",*point);
    return;
}

The compile error that I am getting is -

Compilation error   time: 0 memory: 10320 signal:0
prog.c: In function ‘main’:
prog.c:5:2: warning: implicit declaration of function ‘test’ [-Wimplicit-function-declaration]
  test(line);
  ^~~~
prog.c: At top level:
prog.c:9:6: warning: conflicting types for ‘test’
 void test(int point) {
      ^~~~
prog.c:5:2: note: previous implicit declaration of ‘test’ was here
  test(line);
  ^~~~
prog.c: In function ‘test’:
prog.c:11:14: error: invalid type argument of unary ‘*’ (have ‘int’)
  printf("%c",*point);
              ^~~~~~

Upvotes: 0

Views: 756

Answers (2)

kr1tzy
kr1tzy

Reputation: 148

1) It wants a function prototype or for the function to be declared above your main.

2) The parameter point in 

void test (int point)

is a pointer, not an int.

Upvotes: 0

dbush
dbush

Reputation: 223729

Two problems here.

First, you use the function test before it's declared. So the function is implicitly declared as taking an unspecified number of arguments and returning int, i.e. int test(). This conflict with the definition void test(int point) that appears later.

The second issue is that you pass a char array (which decays to a char *) to test, but the function is expecting an int.

Move the definition of test to before main so that is defined before it's used, and change the point parameter from int to char *.

#include <stdio.h>

void test(char *point) {
    point++;
    printf("%c",*point);
    return;
}

int main(void) {
    char line[4] = "abc";
    test(line);
    return 0;
}

Upvotes: 4

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