printf "%n" specifier not working properly

Question

I copied this code from geeks for geeks.

#include<stdio.h>
  
int main()
{
  int c;
  printf("geeks for %ngeeks ", &c);
  printf("%d", c);
  getchar();
  return 0;
}

It should print the characters from start to %n followed by the number of printed characters:

But when I execute it, it's printing this:

Your code works fine on multiple online compilers. Try using "geeks for %n geeks " instead of "geeks for %ngeeks " and see if there are any noticeable changes. — Kitswas, Apr 15 '21 at 14:39
i don't know, what do you mean with flag ? i tried compile with gcc main.c -o main.exe && main.exe — AhmetEnesKCC, Apr 15 '21 at 14:57
To clarify the previous comment, the value is not assigned to `c`. — anastaciu, Apr 15 '21 at 15:07
@AhmetEnesKCC Depends on your environment. In MSYS2 you can use `pacman` package manager — Eugene Sh., Apr 15 '21 at 15:39
This [post](https://stackoverflow.com/q/61497394/6865932) also has several options, note that you may have to reconfigure your IDE to use the newer compiler. — anastaciu, Apr 15 '21 at 15:49

anastaciu · Accepted Answer · 2021-04-15T15:36:34.187

2

It seems that the problem lies in the fact that older versions of MingW do not set __USE_MINGW_ANSI_STDIO by default, which is not the case for newer versions, what you can do is to manually define it in your program:

# define __USE_MINGW_ANSI_STDIO

#include <stdio.h>

int main()
{
    //...
}

Or use it directly on the compilation command:

gcc main.c -o main.exe -D __USE_MINGW_ANSI_STDIO

edited Apr 15 '21 at 15:36

answered Apr 15 '21 at 15:31

anastaciu

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printf "%n" specifier not working properly

1 Answers1