From 476671741bb07085eec851702a7c3b1e5a4cc0ba Mon Sep 17 00:00:00 2001
From: Gitea <gitea@fake.local>
Date: Sat, 15 Jan 2022 11:50:27 +0800
Subject: [PATCH] add check_pointer.c

---
 check_pointer.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 check_pointer.c

diff --git a/check_pointer.c b/check_pointer.c
new file mode 100644
index 0000000..cc94dee
--- /dev/null
+++ b/check_pointer.c
@@ -0,0 +1,61 @@
+#include <stdio.h>
+
+int main()
+{
+    int a = 1;
+    int b = 2;
+    int c = 3;
+    int d = 4;
+
+    int *pa = &a;
+    int *pb = &b;
+    int **ppa = &pa;
+    int **ppb = &pb;
+
+    printf("%x %x\n", &a, a);
+    printf("%x %x\n", &b, b);
+    printf("%x %x\n", &c, c);
+    printf("%x %x\n", &d, d);
+    printf("%x %x %x\n", &pa, pa, *pa);
+    printf("%x %x %x\n", &pb, pb, *pb);
+    printf("%x %x %x %x\n", &ppa, ppa, *ppa, **ppa);
+    printf("%x %x %x %x\n", &ppb, ppb, *ppb, **ppb);
+
+    ppa = &pb;
+    ppb = &pa;
+
+    printf("%x %x\n", &a, a);
+    printf("%x %x\n", &b, b);
+    printf("%x %x\n", &c, c);
+    printf("%x %x\n", &d, d);
+    printf("%x %x %x\n", &pa, pa, *pa);
+    printf("%x %x %x\n", &pb, pb, *pb);
+    printf("%x %x %x %x\n", &ppa, ppa, *ppa, **ppa);
+    printf("%x %x %x %x\n", &ppb, ppb, *ppb, **ppb);
+
+    *ppa = &c;
+    *ppb = &d;
+
+    printf("%x %x\n", &a, a);
+    printf("%x %x\n", &b, b);
+    printf("%x %x\n", &c, c);
+    printf("%x %x\n", &d, d);
+    printf("%x %x %x\n", &pa, pa, *pa);
+    printf("%x %x %x\n", &pb, pb, *pb);
+    printf("%x %x %x %x\n", &ppa, ppa, *ppa, **ppa);
+    printf("%x %x %x %x\n", &ppb, ppb, *ppb, **ppb);
+
+    **ppa = 5;
+    **ppb = 6;
+
+    printf("%x %x\n", &a, a);
+    printf("%x %x\n", &b, b);
+    printf("%x %x\n", &c, c);
+    printf("%x %x\n", &d, d);
+    printf("%x %x %x\n", &pa, pa, *pa);
+    printf("%x %x %x\n", &pb, pb, *pb);
+    printf("%x %x %x %x\n", &ppa, ppa, *ppa, **ppa);
+    printf("%x %x %x %x\n", &ppb, ppb, *ppb, **ppb);
+
+    return 0;
+}