On compiling the below code compiler showing warning

Question

#include<stdio.h>

struct employee
{
  char name[25] ;
  int id ;
  int age ;
  float inc ;
} b[3] ;

int main()
{
  int i ;
  for(i = 0 ; i < 3 ; i++)
  {
    printf("Enter name , id , age , inc of employee %d :- ",i+1) ;
    scanf("%s%d%d%f",&b[i].name,&b[i].id,&b[i].age,&b[i].inc) ;
  }
  printf("\n") ;
  for(i = 0 ; i < 3 ; i++)
  {
    printf("%s%d%d%f\n",b[i].name,b[i].id,b[i].age,b[i].inc) ;
  }
  return 0 ;
}

Output on compiling :

warning: format ‘%s’ expects argument of type ‘char ’, but argument has type ‘char ()[25]’ [-Wformat=] scanf("%s%d%d%f",&b[i].name,&b[i].id,&b[i].age,&b[i].inc) ;

How to fix the warning ?

An array name, like `b[i].name`, will [decay to a pointer](https://stackoverflow.com/questions/1461432/what-is-array-decaying). No need for the `&`. — Bo Persson, Nov 28 '17 at 20:15
Have you tried referring to the C reference? There is even a working example: http://www.cplusplus.com/reference/cstdio/scanf/ — Nick, Nov 28 '17 at 20:17
Plus, your scanf may not store what you think it will store w.r.t. whitespace or lack thereof, etc. — Nick, Nov 28 '17 at 20:19
@KevinDTimm - The C++ C library is largely the same as ISO1990 C; exactly the same for the purposes of this question. I just linked the first source I knew was reputable. — Nick, Nov 28 '17 at 20:22
@Nick - as these are 2 separate languages, I would expect that there should be a page for `c` — KevinDTimm, Nov 28 '17 at 20:23
Fine: https://www-s.acm.illinois.edu/webmonkeys/book/c_guide/2.12.html#scanf -- but now my eyes hurt. — Nick, Nov 28 '17 at 20:24
@KevinDTimm Yes, http://en.cppreference.com/w/c/io/fscanf or http://www.manpagez.com/man/3/scanf/ for example. — Bob__, Nov 28 '17 at 20:34
@Bob__ : nope (C++ reference C++98, C++03, C++11, C++14, C++17, C++20) — KevinDTimm, Nov 28 '17 at 20:49
@KevinDTimm Do you mind elaborate? I specifically linked to the C documentation page (see the references throughout the whole page and at the bottom in particular) even if that site is well known as C++ reference. — Bob__, Nov 28 '17 at 20:56

score 4 · Answer 1 · answered Nov 28 '17 at 20:16

&b[i].name is a pointer to an array of char (it's a char (*)[25]), but scanf wants a pointer to a char (a char*).

You need to pass a pointer to the array's first element.

You can either get that explicitly with &b[i].name[0], or rely on implicit conversion with just b[i].name

score 2 · Answer 2 · answered Nov 28 '17 at 20:14

2

No need for & on b[i].name as this decomposes to a pointer to the zeroth element already

answered Nov 28 '17 at 20:14

KevinDTimm

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On compiling the below code compiler showing warning

2 Answers2