In case of a loop within the class hierarchie Function::isImplicitlyVirtual_rec() was entering an endless loop. Tracking the previously analyzed types shall prevent this.

lib/symboldatabase.cpp

@@ -2029,7 +2029,7 @@ bool Function::isImplicitlyVirtual(bool defaultVal) const
         return false;
 }
 
-bool Function::isImplicitlyVirtual_rec(const ::Type* baseType, bool& safe) const
+bool Function::isImplicitlyVirtual_rec(const ::Type* baseType, bool& safe, std::deque< const ::Type* > *anchestors) const
 {
     // check each base class
     for (std::size_t i = 0; i < baseType->derivedFrom.size(); ++i) {
@@ -2065,9 +2065,19 @@ bool Function::isImplicitlyVirtual_rec(const ::Type* baseType, bool& safe) const
             }
 
             if (!baseType->derivedFrom[i].type->derivedFrom.empty()) {
-                // avoid endless recursion, see #5289 Crash: Stack overflow in isImplicitlyVirtual_rec when checking SVN
-                if ((baseType != baseType->derivedFrom[i].type) && isImplicitlyVirtual_rec(baseType->derivedFrom[i].type, safe))
-                    return true;
+                // avoid endless recursion, see #5289 Crash: Stack overflow in isImplicitlyVirtual_rec when checking SVN and
+                // #5590 with a loop within the class hierarchie.
+                // We do so by tracking all previously checked types in a deque.
+                std::deque< const ::Type* > local_anchestors;
+                if (!anchestors) {
+                    anchestors=&local_anchestors;
+                }
+                anchestors->push_back(baseType);
+                if (std::find(anchestors->begin(), anchestors->end(), baseType->derivedFrom[i].type)==anchestors->end()) {
+                    if (isImplicitlyVirtual_rec(baseType->derivedFrom[i].type, safe, anchestors))  {
+                        return true;
+                    }
+                }
             }
         } else {
             // unable to find base class so assume it has no virtual function

lib/symboldatabase.h

@@ -24,6 +24,7 @@
 #include <string>
 #include <list>
 #include <vector>
+#include <deque>
 #include <set>
 #include <algorithm>
 
@@ -603,7 +604,7 @@ public:
     static bool argsMatch(const Scope *info, const Token *first, const Token *second, const std::string &path, unsigned int depth);
 
 private:
-    bool isImplicitlyVirtual_rec(const ::Type* type, bool& safe) const;
+    bool isImplicitlyVirtual_rec(const ::Type* type, bool& safe, std::deque<const ::Type* > *anchestors = nullptr) const;
 };
 
 class CPPCHECKLIB Scope {

test/testsymboldatabase.cpp

@@ -1818,6 +1818,27 @@ private:
                           "   }\n"
                           "};");
             ASSERT(db && db->findScopeByName("Bar") && !db->findScopeByName("Bar")->functionList.front().isImplicitlyVirtual(false));
+            ASSERT_EQUALS(1, db->findScopeByName("Bar")->functionList.size());
+        }
+
+        // #5590
+        {
+            GET_SYMBOL_DB("class InfiniteB : InfiniteA {\n"
+                          "    class D {\n"
+                          "    };\n"
+                          "};\n"
+                          "namespace N {\n"
+                          "    class InfiniteA : InfiniteB {\n"
+                          "    };\n"
+                          "}\n"
+                          "class InfiniteA : InfiniteB {\n"
+                          "    void foo();\n"
+                          "};\n"
+                          "void InfiniteA::foo() {\n"
+                          "    C a;\n"
+                          "}");
+            //ASSERT(db && db->findScopeByName("InfiniteA") && !db->findScopeByName("InfiniteA")->functionList.front().isImplicitlyVirtual());
+            TODO_ASSERT_EQUALS(1, 0, db->findScopeByName("InfiniteA")->functionList.size());
         }
 
     }

test/testunusedprivfunc.cpp

@@ -72,6 +72,7 @@ private:
 
         TEST_CASE(multiFile);
         TEST_CASE(unknownBaseTemplate); // ticket #2580
+        TEST_CASE(hierarchie_loop); // ticket 5590
     }
 
 
@@ -692,6 +693,25 @@ private:
         ASSERT_EQUALS("", errout.str());
     }
 
+    void hierarchie_loop() {
+        check("class InfiniteB : InfiniteA {\n"
+              "    class D {\n"
+              "    };\n"
+              "};\n"
+              "namespace N {\n"
+              "    class InfiniteA : InfiniteB {\n"
+              "    };\n"
+              "}\n"
+              "class InfiniteA : InfiniteB {\n"
+              "    void foo();\n"
+              "};\n"
+              "void InfiniteA::foo() {\n"
+              "    C a;\n"
+              "}");
+
+        ASSERT_EQUALS("[test.cpp:10]: (style) Unused private function: 'InfiniteA::foo'\n", errout.str());
+    }
+
 };
 
 REGISTER_TEST(TestUnusedPrivateFunction)