[C] 함수포인터

출처 : http://netpyoung.tistory.com/72

compileLanguage/C

2010/01/31 03:09

http://netpyoung.tistory.com/78과 이어지는 내용입니다.
포인터의 이해와 함수포인터의 이해가 부족하다면 위 링크를 한번 읽고 오시면 좋을 것 같습니다.

[pyoung@hwarang temp]$ cat test01.c
#include <stdio.h>

void hellow(int a)
{
  printf("hellow world\n%d\n", a);
}

int hellow2(void)
{
  printf("hellow 2\n");
  return 2;
}

void hellow3(int a, int b)
{
  printf("a+b = %d\n", a+b);
}

double hellow4(double a, int b)
{
  return -1;
}

void hellow5(void)
{
  printf("hi\n");
}

int main()
{
  void (* p)(int) = hellow;
  p(1);

  int (* p2)(void) = hellow2;
  int i = 0;
  i = p2();
  printf("%d\n", i);

  void (* p3) (int a , int b) = hellow3;
  p3(1 ,2 );

  double (* p4) (double a, int b) = hellow4;
  i = p4(1,2);
  printf("%d\n", i);

  void (* p5)() = hellow5;
  p5();

  return 0;
}
[pyoung@hwarang temp]$ ./test01
hellow world
1
hellow 2
2
a+b = 3
-1
hi

[pyoung@hwarang temp]$ cat test02.c
#include <stdio.h>

int hellow(int a, int b) {
  printf("hellow world\n");
  return 0;
};

int (*func(void)) (int, int) {
  return hellow;
}

int main()
{
  func()(1 ,2);
  return 0;
}
[pyoung@hwarang temp]$ ./test02
hellow world

매번 느끼지만 스터디할때마다.. 신기하다는...


함수 포인터 선언
>> 리턴 (* 함수)(인자값)

pyoung@hwarang:~/myHome/signal$ cat ./test02.c
#include <stdio.h>

int multi(int one) {
  printf("multi called\n");
  return one;
}

void call_multi(int(*p)(int one)) {
  printf("%d, call_multi\n", p(777));
}

int main()
{
  call_multi(multi);
  return 0;
}
pyoung@hwarang:~/myHome/signal$ ./test02
multi called
777, call_multi

pyoung@hwarang:~/myHome/signal$ cat ./signal1.c
#include <stdio.h>
#include <signal.h>

void foo(void) {
  printf("foo called\n");
}

void bar(void) {
  printf("bar called\n");
}

void my_sig(int signo) {
  printf("my_sig called\n");
}

int main()
{
  void (*p[])(void) = {foo, bar};
  int i;
  int choice = 0;
  for(i=0; i<2; ++i)
    p[i]();
  //foo(), bar()호출

  for(choice; choice<2; ++choice) {
    switch(choice) {
    case 0:
      foo();
      break;
    case 1:
      bar();
      break;
    }
    p[choice]();
  }
  return 0;
}
/*
case 0: 에서 foo()호출
p[0](); 에서 foo()호출
case 1: 에서 bar()호출
p[1](); 에서 bar()호출
*/
pyoung@hwarang:~/myHome/signal$ ./signal1
foo called
bar called
foo called
foo called
bar called
bar called

pyoung@hwarang:~/myHome/signal$ cat ./signal2.c
#include <stdio.h>

void aaa(void);
void bbb(void(*p)(void));

int main(void) {
  bbb(aaa);
  return 0;
}

void aaa(void) {
  printf("aaa called\n");
}

void bbb(void(*p)(void)) {
  p();
  printf("bbb called\n");
}
pyoung@hwarang:~/myHome/signal$ ./signal2
aaa called
bbb called

pyoung@hwarang:~/myHome/signal$ cat ./signal3.c
#include <stdio.h>

void aaa(int a) {
  printf("aaa() called\n");
  printf("%d\n", a);
}

void (* bbb(void)) (int a) {
  printf("bbb() called\n");
  return aaa;
}

int main(void) {
  bbb()(1);
  return 0;
}

pyoung@hwarang:~/myHome/signal$ ./signal3
bbb() called
aaa() called
1

pyoung@hwarang:~/myHome/signal$ cat ./signal4.c
#include <stdio.h>

void aaa(void) {
  printf("aaa called\n");
}

void (* bbb(void (*p) (void))) (void) {
  p();
  printf("bbb called\n");
  return aaa;
}

int main(void) {
  bbb(aaa)();
  return 0;
}

pyoung@hwarang:~/myHome/signal$ ./signal4
aaa called
bbb called
aaa called

pyoung@hwarang:~/myHome/signal$ cat ./signal5.c
#include <stdio.h>

int (* aaa(void)) [2] {
  static int a[2][2] = {{1,2},{3,4}};
  printf("aaa called\n");
  return a;
}


int (* (* bbb(void))(void))[2] {
  printf("bbb called\n");
  return aaa;
}


int main(void) {
  int (*ret)[2];
  int (* (* (*p[][2])(void)) (void))[2] =
    { {bbb, bbb}, {bbb, bbb}};

  int (* (* (* (*p1)[2]) (void))(void))[2] = p;

  ret = ((* (* (* (*p1)[2])))()());

  printf("%d\n", *ret[0]);
  return 0;
}

pyoung@hwarang:~/myHome/signal$ ./signal5
bbb called
aaa called
1

pyoung@hwarang:~/myHome/signal$ cat ./signal6.c
#include <stdio.h>

typedef int (*FP1)[2];
typedef FP1 (*FP2)(void);
typedef FP2 (*FP3)(void);
typedef FP3 (*FP4)[2];

FP1 aaa(void) {
  static int a[2][2];
  printf("aaa called\n");
  return a;
}


FP2 bbb(void) {
  printf("bbb called\n");
  return aaa;
}

int main() {
  int (*ret)[2];
  FP3 p[][2] = {{bbb,bbb}, {bbb,bbb}};
  FP4 p1 = p;
  ret = ((* (* (* (*p1) [2])))()());
  printf("%d\n", *ret[0]);
  return 0;
}


pyoung@hwarang:~/myHome/signal$ ./signal6
bbb called
aaa called
0

void  (*signal(int  signum,   void (*p)(int) ) )(int);
스터디장 왈 :
signal은 signum이라는 int형 인자와 void (*)(int)형의 함수 포인터 p 인자를 가지는 함수이며,
리턴값은 void (*)(int)형의 함수 포인터입니다
>>> (void(*)(int)) signal(int signum, (void (*) (int))p)