From 4e1d606af5d95e007ba90c13fc2dc61c39905e27 Mon Sep 17 00:00:00 2001
From: Gabriel Ferreira <gabrielcarvfer@gmail.com>
Date: Mon, 1 Aug 2022 23:16:40 -0300
Subject: [PATCH] bindings: fix segmentation violation in python scripts

And move sample-rng-plot.py code to a main function
---
 examples/wireless/mixed-wired-wireless.py | 11 ++++-
 src/core/examples/sample-rng-plot.py      | 60 +++++++++++++----------
 utils/python-unit-tests.py                |  8 +++
 3 files changed, 50 insertions(+), 29 deletions(-)

diff --git a/examples/wireless/mixed-wired-wireless.py b/examples/wireless/mixed-wired-wireless.py
index 76c4b91bb..71b3d452e 100644
--- a/examples/wireless/mixed-wired-wireless.py
+++ b/examples/wireless/mixed-wired-wireless.py
@@ -235,7 +235,7 @@ def main(argv):
     #  Reset the address base-- all of the 802.11 networks will be in
     #  the "10.0" address space
     ipAddrs.SetBase(ns.network.Ipv4Address("10.0.0.0"), ns.network.Ipv4Mask("255.255.255.0"))
-
+    tempRef = []  # list of references to be held to prevent garbage collection
     for i in range(backboneNodes):
         print ("Configuring wireless network for backbone node ", i)
         #
@@ -279,11 +279,18 @@ def main(argv):
         #  the network mask initialized above
         #
         ipAddrs.NewNetwork()
+
+        # This call returns an instance that needs to be stored in the outer scope
+        # not to be garbage collected when overwritten in the next iteration
+        subnetAlloc = ns.mobility.ListPositionAllocator()
+
+        # Appending the object to a list is enough to prevent the garbage collection
+        tempRef.append(subnetAlloc)
+
         #
         #  The new wireless nodes need a mobility model so we aggregate one
         #  to each of the nodes we just finished building.
         #
-        subnetAlloc = ns.mobility.ListPositionAllocator()
         for j in range(infra.GetN()):
             subnetAlloc.Add(ns.core.Vector(0.0, j, 0.0))
 
diff --git a/src/core/examples/sample-rng-plot.py b/src/core/examples/sample-rng-plot.py
index 2f1d8c8e2..936ec3121 100644
--- a/src/core/examples/sample-rng-plot.py
+++ b/src/core/examples/sample-rng-plot.py
@@ -29,37 +29,43 @@ import sys
 import argparse
 from ns import ns
 
-parser = argparse.ArgumentParser("sample-rng-plot")
-parser.add_argument("--not-blocking",
-                    action="store_true",
-                    default=False)
-args = parser.parse_args(sys.argv[1:])
 
-# mu, var = 100, 225
+def main():
+    parser = argparse.ArgumentParser("sample-rng-plot")
+    parser.add_argument("--not-blocking",
+                        action="store_true",
+                        default=False)
+    args = parser.parse_args(sys.argv[1:])
 
-## Random number generator.
-rng = ns.CreateObject("NormalRandomVariable")
-rng.SetAttribute("Mean", ns.DoubleValue(100.0))
-rng.SetAttribute("Variance", ns.DoubleValue(225.0))
+    # mu, var = 100, 225
 
-## Random number samples.
-x = [rng.GetValue() for t in range(10000)]
+    ## Random number generator.
+    rng = ns.CreateObject("NormalRandomVariable")
+    rng.SetAttribute("Mean", ns.DoubleValue(100.0))
+    rng.SetAttribute("Variance", ns.DoubleValue(225.0))
 
-# the histogram of the data
+    ## Random number samples.
+    x = [rng.GetValue() for t in range(10000)]
 
-## Make a probability density histogram
-density = 1
-## Plot color
-facecolor='g'
-## Plot alpha value (transparency)
-alpha=0.75
+    # the histogram of the data
 
-# We don't really need the plot results, we're just going to show it later.
-# n, bins, patches = plt.hist(x, 50, density=1, facecolor='g', alpha=0.75)
-n, bins, patches = plt.hist(x, 50, density=True, facecolor='g', alpha=0.75)
+    ## Make a probability density histogram
+    density = 1
+    ## Plot color
+    facecolor = 'g'
+    ## Plot alpha value (transparency)
+    alpha = 0.75
 
-plt.title('ns-3 histogram')
-plt.text(60, .025, r'$\mu=100,\ \sigma=15$')
-plt.axis([40, 160, 0, 0.03])
-plt.grid(True)
-plt.show(block=not args.not_blocking)
+    # We don't really need the plot results, we're just going to show it later.
+    # n, bins, patches = plt.hist(x, 50, density=1, facecolor='g', alpha=0.75)
+    n, bins, patches = plt.hist(x, 50, density=True, facecolor='g', alpha=0.75)
+
+    plt.title('ns-3 histogram')
+    plt.text(60, .025, r'$\mu=100,\ \sigma=15$')
+    plt.axis([40, 160, 0, 0.03])
+    plt.grid(True)
+    plt.show(block=not args.not_blocking)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/utils/python-unit-tests.py b/utils/python-unit-tests.py
index 1908d3f52..a049db191 100644
--- a/utils/python-unit-tests.py
+++ b/utils/python-unit-tests.py
@@ -214,6 +214,8 @@ class TestSimulator(unittest.TestCase):
         self.assertTrue(self._received_packet is not None)
         self.assertEqual(self._received_packet.GetSize(), 19)
 
+        # Delete Ptr<>'s on the python side to let C++ clean them
+        del internet
 
     def testAttributes(self):
         """! Test attributes function
@@ -243,6 +245,9 @@ class TestSimulator(unittest.TestCase):
         mobility.GetAttribute("PositionAllocator", ptr2)
         self.assertNotEqual(ptr.GetObject(), ns.core.Ptr["Object"](ns.cppyy.nullptr))
 
+        # Delete Ptr<>'s on the python side to let C++ clean them
+        del queue, mobility, ptr, ptr2
+
     def testIdentity(self):
         """! Test identify
         @param self this object
@@ -257,6 +262,9 @@ class TestSimulator(unittest.TestCase):
 
         self.assertEqual(c1, c2)
 
+        # Delete Ptr<>'s on the python side to let C++ clean them
+        del csma, channel
+
     def testTypeId(self):
         """! Test type ID
         @param self this object