[PyROOT] Add regression test for #15703

Author: vepadulano

bindings/pyroot/pythonizations/test/CMakeLists.txt

@@ -191,3 +191,6 @@ endif()
 
 # TComplex pythonizations
 ROOT_ADD_PYUNITTEST(pyroot_tcomplex tcomplex_operators.py)
+
+# Tests with memory usage
+ROOT_ADD_PYUNITTEST(pyroot_memory memory.py)

bindings/pyroot/pythonizations/test/memory.py

@@ -0,0 +1,46 @@
+import gc
+import ROOT
+import unittest
+
+
+class MemoryStlString(unittest.TestCase):
+
+    def test_15703(self):
+        """Regression test for https://github.com/root-project/root/issues/15703"""
+
+        ROOT.gInterpreter.Declare("""
+        #include <string>
+        class foo {
+            public:
+            const std::string leak (std::size_t size) const {
+                std::string result;
+                result.reserve(size);
+                return result;
+            }
+        };
+                                  
+        auto get_rss_MB() {
+            ProcInfo_t info;
+            gSystem->GetProcInfo(&info);
+            return info.fMemResident;
+        }
+        """)
+        obj = ROOT.foo()
+        for _ in range(1000000):
+            __ = obj.leak(2048)
+
+        gc.collect()
+
+        before = ROOT.get_rss_MB()
+
+        for _ in range(1000000):
+            __ = obj.leak(2048)
+
+        gc.collect()
+        after = ROOT.get_rss_MB()
+        delta = after - before
+        self.assertLess(delta, 4)
+
+
+if __name__ == '__main__':
+    unittest.main()