Why my computer crashes when I execute this code in c?

Question

I was practicing about structs in C, so I've tried to execute 2 times this code and twice the computer crashes. I've had turn off the computer twice since my computer crashes.

Compiler is GCC (About MinGW on windows platform). The code is following :

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

struct person {
    char name[50];
    int age;
    int document;   

};

int main(void){
    struct person p1;
    printf("Data of the  first person\n\n");
    printf("age:  ");
    fflush (stdin);
    scanf("%i",p1.age );
    printf("Document:  ");
    fflush(stdin);
    scanf("%i",p1.document);

    printf("Age is: %i and document is: %i ",p1.age,p1.document);
    return 0;
}

Sincerely, NIN.

UPDATE....

Bad news. Now Avast says I`ve created a virus. Therefore Avast delete my exe:

Should I report as false positive or not ?

[undefined behavior](https://en.wikipedia.org/wiki/Undefined_behavior) — Eugene Sh., Aug 31 '16 at 17:33
@NIN does your computer really crashes? You see blue screen, and have to reboot it? — fukanchik, Aug 31 '16 at 17:34
Surprisingly your code worked fine for me on windows. Which windows version do you use? — fukanchik, Aug 31 '16 at 17:49
I also tried to compile it with MSVC and now it shows dialog saying "Program stopped working". I am on windows 7 — fukanchik, Aug 31 '16 at 17:52
@fukanchik Should we repeat here the "nasal demons" thing about UB? — Eugene Sh., Aug 31 '16 at 17:58
@EugeneSh. I am more interested here in Windows behaviour than in program itself. — fukanchik, Aug 31 '16 at 18:02
@fukanchik Well, it should not freeze or crash because of some bad user-space program, that's for sure.. — Eugene Sh., Aug 31 '16 at 18:03
fukanchik. Why I need implement `stdout` rather than `stdin` — NIN, Aug 31 '16 at 18:13
See [Using `fflush(stdin)`](http://stackoverflow.com/questions/2979209/using-fflushstdin) for more information about when it is OK to use it (Windows) and when it is not (anywhere else — to a first approximation). — Jonathan Leffler, Aug 31 '16 at 18:36

David Schwartz · Accepted Answer · 2016-08-31T18:28:04.033

6

scanf("%i",p1.age );

When you call scanf, p1.age is an integer with no particular value. So you are asking scanf to store the value you input in no particular place. It's not surprising this causes a crash. You want:

scanf("%i", &p1.age );

This tells scanf to read in an integer and store it at the address of p1.age.

It's surprising your compiler didn't give you a warning. Are you sure you have all of its warnings enabled?

When I try to compile this, I get appropriate warnings:

warning: format ‘%i’ expects argument of type ‘int *’, but argument 2 has type ‘int’ [-Wformat=]

Update: Your anti-virus has heuristics that block software that has suspicious behavior. Your code has bugs, and your anti-virus doesn't know that they're just mistakes and not attempts to do something nefarious. It sounds like you don't have a very good environment set up for experimentation. Let me guess -- you're doing all this from a Windows administrator account.

edited Aug 31 '16 at 18:28

answered Aug 31 '16 at 17:30

David Schwartz

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*It's surprising your compiler didn't give you a warning* - who said it didn't? :) – Eugene Sh. Aug 31 '16 at 17:31
well, At least all warning are by default David. – NIN Aug 31 '16 at 17:32
WOW , I thought I didn't need the & operator since It was a struct in C code – NIN Aug 31 '16 at 17:35
David now avast says I've created a virus – NIN Aug 31 '16 at 18:23
1

It says you've written code that has suspicious behavior. That's likely true, since you don't quite know what you're doing. – David Schwartz Aug 31 '16 at 18:26
So What should I chance in my code to eliminate that warning from my antivirus ?. I mean, How could I improving the code ? – NIN Aug 31 '16 at 18:46

Why my computer crashes when I execute this code in c?

1 Answers1