Why this code compile but not running

Question

Why this code compile but not running?

int main() {
     char *s;

     scanf("%15s", s);
     puts(s);
 }

I'm sorry to have to inform you that compiling fine and then not running correctly is normal behaviour. — ThingyWotsit, Apr 03 '17 at 12:53
the answers answer precisely as to what is wrong but I do feel that its missing the return statement — B P, Apr 03 '17 at 12:56
@BP you do not need a return statement in `main` according to the C11 standard. — JeremyP, Apr 03 '17 at 13:21

score 2 · Answer 1 · answered Apr 03 '17 at 12:52

2

Because s is an uninitialized pointer, you cannot store data there (since there "is no there there").

Try:

char s[32];

instead, that gives you 32 characters' worth of room into which scanf() can write.

answered Apr 03 '17 at 12:52

unwind

391,730
64
469
606

score 2 · Answer 2 · answered Apr 03 '17 at 12:53

2

You need to provide memory for scanf(...) The char *s is only a pointer to some memory, but not he memory itself. You can either malloc(...) the memory and have s point to it, or allocate it locally on the stack by char s[16]

answered Apr 03 '17 at 12:53

cleblanc

3,678
1
13
16

score 1 · Answer 3 · answered Apr 03 '17 at 12:54

1

For starters, provide a proper buffer to the scanf call. For example, instead of char *s which is simply an uninitialized pointer, try char s[128].

answered Apr 03 '17 at 12:54

Phil Brubaker

1,257
3
11
14

Why this code compile but not running

3 Answers3