refs #3179 std::string COW issue workaround (#3180)

doxygen/lang/900_release_notes.dox.tmpl

@@ -189,6 +189,8 @@
       - Command line utils display source line code when interrupted
 
     @subsection qore_09_bug_fixes Bug Fixes in Qore
+    - worked around a potential COW bug in \c std::string in GNU libdstdc++ 6+
+      (<a href="https://github.com/qorelanguage/qore/issues/3179">issue 3179</a>)
     - fixed a bug with simple additional and subtraction with mixed @ref timeout_type "timeout" and
       @ref date_type "date" values; updated docs that arithmetic operations with timeout values are not recommended
       and can return unexpected values in some situations

examples/test/qore/misc/issue3179/issue3179.qm

@@ -0,0 +1,18 @@
+%new-style
+%require-types
+%strict-args
+%enable-all-warnings
+
+module issue3179 {
+    version = "1.0";
+    desc = "issue 3179 test";
+    author = "Qore Technologies, s.r.o.";
+    url = "https://qore.org";
+    license = "MIT";
+}
+
+public class Disappear {
+    static string get() {
+        return "str";
+    }
+}

examples/test/qore/misc/issue3179/issue3179.qtest

@@ -0,0 +1,40 @@
+#!/usr/bin/env qore
+
+%new-style
+%require-types
+%strict-args
+%enable-all-warnings
+
+%requires ../../../../../qlib/Util.qm
+%requires ../../../../../qlib/QUnit.qm
+%requires ./issue3179.qm
+
+%requires reflection
+
+%exec-class Issue3179Test
+
+class Issue3179Test inherits QUnit::Test {
+    constructor() : QUnit::Test("Issue3179Test", "1.0") {
+        addTestCase("issue 3179", \issue3179());
+
+        set_return_value(main());
+    }
+
+    issue3179() {
+        for (int i = 0; i < 3; ++i) {
+            doTest();
+        }
+    }
+
+    private doTest() {
+        Program p(PO_NO_INHERIT_USER_CLASSES);
+        p.importClass("Disappear");
+        p.parse("string sub get() { return Disappear::get(); }", "");
+        assertEq("str", p.callFunction("get"));
+        assertEq("str", Disappear::get());
+
+        Class cls = Class::forName("Disappear");
+        AbstractMethod m = cls.findMethod("get").method;
+        assertEq("Disappear", m.getClass().getName());
+    }
+}

lib/QoreClass.cpp

@@ -481,7 +481,8 @@ qore_class_private::qore_class_private(QoreClass* n_cls, std::string&& nme, int6
 
 // only called while the parse lock for the QoreProgram owning "old" is held
 qore_class_private::qore_class_private(const qore_class_private& old, qore_ns_private* ns, QoreProgram* spgm, const char* new_name, bool inject, const qore_class_private* injectedClass)
-   : name(new_name ? new_name : old.name),
+   // issue #3179: we force a deep copy of "name" to work around COW issues with std::string with GNU libstdc++ 6+
+   : name(new_name ? new_name : old.name.c_str()),
      ns(ns),
      ahm(old.ahm),
      constlist(old.constlist, 0, this),    // committed constants