[cling] Add test for template unloading

Author: devajithvs

roottest/root/meta/redeclUnload/CMakeLists.txt

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+include_directories(${CMAKE_CURRENT_SOURCE_DIR}/inc)
+
+ROOTTEST_GENERATE_REFLEX_DICTIONARY(TemplateRedecl
+                                    inc/RedeclTrigger.h
+                                    SELECTION inc/redecl_selection.xml
+                                    FIXTURES_SETUP root-meta-redeclUnload-TemplateRedecl-fixture)
+
+ROOTTEST_ADD_TEST(templateRedeclUnload
+                  MACRO testTemplateRedeclUnload.C
+                  ROOTEXE_OPTS -e "gInterpreter->AddIncludePath(\"-I${CMAKE_CURRENT_SOURCE_DIR}\")"
+                  OUTREF TemplateRedeclUnload.ref
+                  FIXTURES_REQUIRED root-meta-redeclUnload-TemplateRedecl-fixture)

roottest/root/meta/redeclUnload/TemplateRedeclUnload.ref

@@ -0,0 +1 @@
+

roottest/root/meta/redeclUnload/inc/RedeclTrigger.h

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+// Two wrappers are needed to reproduce the assertion with broken redecl chain.
+template <typename T>
+class Wrapper1 {};
+template <typename T>
+class Wrapper2 {};
+
+class RandomClass {};
+Wrapper1<Wrapper2<RandomClass>> var;

roottest/root/meta/redeclUnload/inc/redecl_selection.xml

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+<lcgdict>
+   <class name="RandomClass" splitLevel="0"/>
+   <class name="Wrapper1<Wrapper2<RandomClass>>" splitLevel="0"/>
+</lcgdict>

roottest/root/meta/redeclUnload/testTemplateRedeclUnload.C

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+void testTemplateRedeclUnload()
+{
+   gROOT->ProcessLine("gSystem->Load(\"libTemplateRedecl_dictrflx\");");
+   gROOT->ProcessLine("gInterpreter->AutoParse(\"RandomClass\");");
+
+   // Undo the last 2 commands, which unloads the templates.
+   gROOT->ProcessLine(".undo 2");
+
+   // Before the fix: cling crashes here with:
+   //   "Passed first decl twice, invalid redecl chain!"
+   gROOT->ProcessLine("RandomClass obj;");
+}