From eec8452546d6630ecb479b93d1d95c1901b97e61 Mon Sep 17 00:00:00 2001
From: Peter Gerwinski <peter.gerwinski@hs-bochum.de>
Date: Mon, 13 Jun 2022 08:17:19 +0200
Subject: [PATCH] Beispiele 9.6.2022
---
20220609/shared-pointer-01.cpp | 9 +++++++++
20220609/shared-pointer-02.cpp | 10 ++++++++++
20220609/shared-pointer-03.cpp | 11 +++++++++++
20220609/shared-pointer-04.cpp | 10 ++++++++++
20220609/shared-pointer-05.cpp | 15 +++++++++++++++
20220609/shared-pointer-06.cpp | 15 +++++++++++++++
20220609/shared-pointer-07.cpp | 14 ++++++++++++++
20220609/shared-pointer-08.cpp | 17 +++++++++++++++++
20220609/shared-pointer-09.cpp | 20 ++++++++++++++++++++
9 files changed, 121 insertions(+)
create mode 100644 20220609/shared-pointer-01.cpp
create mode 100644 20220609/shared-pointer-02.cpp
create mode 100644 20220609/shared-pointer-03.cpp
create mode 100644 20220609/shared-pointer-04.cpp
create mode 100644 20220609/shared-pointer-05.cpp
create mode 100644 20220609/shared-pointer-06.cpp
create mode 100644 20220609/shared-pointer-07.cpp
create mode 100644 20220609/shared-pointer-08.cpp
create mode 100644 20220609/shared-pointer-09.cpp
diff --git a/20220609/shared-pointer-01.cpp b/20220609/shared-pointer-01.cpp
new file mode 100644
index 0000000..c12bdc6
--- /dev/null
+++ b/20220609/shared-pointer-01.cpp
@@ -0,0 +1,9 @@
+#include <stdio.h>
+
+int main ()
+{
+ int *a = new int (42);
+ int *b = a;
+ printf ("b = %d\n", *b);
+ return 0;
+}
diff --git a/20220609/shared-pointer-02.cpp b/20220609/shared-pointer-02.cpp
new file mode 100644
index 0000000..f54578b
--- /dev/null
+++ b/20220609/shared-pointer-02.cpp
@@ -0,0 +1,10 @@
+#include <stdio.h>
+
+int main ()
+{
+ int *a = new int (42);
+ int *b = a;
+ delete a;
+ printf ("b = %d\n", *b);
+ return 0;
+}
diff --git a/20220609/shared-pointer-03.cpp b/20220609/shared-pointer-03.cpp
new file mode 100644
index 0000000..fac8189
--- /dev/null
+++ b/20220609/shared-pointer-03.cpp
@@ -0,0 +1,11 @@
+#include <stdio.h>
+
+int main ()
+{
+ int *a = new int (42);
+ int *b = a;
+ delete a;
+ printf ("b = %d\n", *b);
+ delete b;
+ return 0;
+}
diff --git a/20220609/shared-pointer-04.cpp b/20220609/shared-pointer-04.cpp
new file mode 100644
index 0000000..97031a4
--- /dev/null
+++ b/20220609/shared-pointer-04.cpp
@@ -0,0 +1,10 @@
+#include <stdio.h>
+#include <memory>
+
+int main ()
+{
+ std::shared_ptr <int> a (new int (42));
+ std::shared_ptr <int> b = a;
+ printf ("%d\n", *b);
+ return 0;
+}
diff --git a/20220609/shared-pointer-05.cpp b/20220609/shared-pointer-05.cpp
new file mode 100644
index 0000000..b1d3c60
--- /dev/null
+++ b/20220609/shared-pointer-05.cpp
@@ -0,0 +1,15 @@
+#include <stdio.h>
+#include <memory>
+
+int main ()
+{
+ std::shared_ptr <int> b;
+ {
+ std::shared_ptr <int> a (new int (42));
+ b = a;
+ // Ohne die Zuweisung an b würde hier der für die Integer allozierte Speicher
+ // automatisch freigegeben, sobald der Zeiger a verschwindet.
+ }
+ printf ("%d\n", *b);
+ return 0;
+}
diff --git a/20220609/shared-pointer-06.cpp b/20220609/shared-pointer-06.cpp
new file mode 100644
index 0000000..18305fb
--- /dev/null
+++ b/20220609/shared-pointer-06.cpp
@@ -0,0 +1,15 @@
+#include <stdio.h>
+#include <memory>
+
+int main ()
+{
+ int *b;
+ {
+ int *a = new int (42);
+ b = a;
+ // Ohne die Zuweisung an b würde hier der für die Integer allozierte Speicher
+ // nicht automatisch freigegeben, sobald der Zeiger a verschwindet. --> Speicherleck
+ }
+ printf ("%d\n", *b);
+ return 0;
+}
diff --git a/20220609/shared-pointer-07.cpp b/20220609/shared-pointer-07.cpp
new file mode 100644
index 0000000..6ed2dec
--- /dev/null
+++ b/20220609/shared-pointer-07.cpp
@@ -0,0 +1,14 @@
+#include <stdio.h>
+#include <memory>
+
+int main ()
+{
+ int *b;
+ {
+ int *a = new int (42);
+ b = a;
+ delete a; // Problem: b zeigt noch auf den freigegebenen Speicher.
+ }
+ printf ("%d\n", *b);
+ return 0;
+}
diff --git a/20220609/shared-pointer-08.cpp b/20220609/shared-pointer-08.cpp
new file mode 100644
index 0000000..033d1f6
--- /dev/null
+++ b/20220609/shared-pointer-08.cpp
@@ -0,0 +1,17 @@
+#include <stdio.h>
+#include <memory>
+
+int main ()
+{
+ std::weak_ptr <int> b;
+ {
+ std::shared_ptr <int> a (new int (42));
+ b = a; // zeigt auf denselben Speicherplatz, ist aber kein "Besitzer",
+ } // d.h., mit dem Verschwinden von a wird der Speicherplatz freigegeben.
+
+ auto c = b.lock (); // Prüfe, ob der Speicher noch da ist.
+ // Falls ja, erzeuge einen shared_ptr c.
+
+ printf ("%d\n", *c); // c == NULL
+ return 0;
+}
diff --git a/20220609/shared-pointer-09.cpp b/20220609/shared-pointer-09.cpp
new file mode 100644
index 0000000..82ba13b
--- /dev/null
+++ b/20220609/shared-pointer-09.cpp
@@ -0,0 +1,20 @@
+#include <stdio.h>
+#include <memory>
+
+int main ()
+{
+ std::weak_ptr <int> b;
+ {
+ std::shared_ptr <int> a (new int (42));
+ b = a; // zeigt auf denselben Speicherplatz, ist aber kein "Besitzer",
+ } // d.h., mit dem Verschwinden von a wird der Speicherplatz freigegeben.
+
+ auto c = b.lock (); // Prüfe, ob der Speicher noch da ist.
+ // Falls ja, erzeuge einen shared_ptr c.
+
+ if (c) // c == NULL, weil der Speicherplatz bereits freigegeben wurde.
+ printf ("%d\n", *c);
+ else
+ printf ("Speicher wurde bereits freigegeben.\n");
+ return 0;
+}
--
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