TCling: Register and print list of autoloaded libraries.

Use `gInterpreter->Print(autoloaded);` to print a list
of the libraries that have been automaticaly loaded during
TClass::GetClass and due to a symbol requested during code
interpretation.

Author: pcanal

core/base/src/TROOT.cxx

@@ -2202,6 +2202,9 @@ Int_t TROOT::LoadClass(const char * /*classname*/, const char *libname,
          // TSystem::Load returns 1 when the library was already loaded, return success in this case.
          if (err == 1)
             err = 0;
+         if (err == 0)
+            // Register the Autoloading of the library
+            gCling->RegisterAutoLoadedLibrary(libname);
          return err;
       }
    } else {

core/meta/inc/TInterpreter.h

@@ -194,6 +194,7 @@ class TInterpreter : public TNamed {
    virtual void     AddAvailableIndentifiers(TSeqCollection&) = 0;
    virtual void     RegisterTClassUpdate(TClass *oldcl,DictFuncPtr_t dict) = 0;
    virtual void     UnRegisterTClassUpdate(const TClass *oldcl) = 0;
+   virtual void     RegisterAutoLoadedLibrary(const char *libname) = 0;
    virtual Int_t    SetClassSharedLibs(const char *cls, const char *libs) = 0;
    virtual void     SetGetline(const char*(*getlineFunc)(const char* prompt),
                                void (*histaddFunc)(const char* line)) = 0;

core/metacling/src/TCling.cxx

@@ -2676,6 +2676,11 @@ void TCling::Print(Option_t *option) const
          for (auto & cls : fAutoParseClasses) {
             std::cout << "  " << cls << std::endl;
          }
+      } else if (!strcmp(option, "autoloaded")) {
+         std::cout << "Auto loaded libraries:" << std::endl;
+         for (auto & lib : fAutoLoadedLibraries) {
+            std::cout << "  " << lib << std::endl;
+         }
       } else {
          ::Error("TCling::Print", "Unknown option '%s'", option);
       }
@@ -3452,6 +3457,14 @@ static bool StartsWithStrLit(const char *haystack, const char (&needle)[N]) {
 }
 }
 
+////////////////////////////////////////////////////////////////////////////////
+/// Register that a library was autoloaded either to provide a 'missing' symbol
+/// or to provide a class (see TClass::GetClass and TROOT::LoadClass).
+void TCling::RegisterAutoLoadedLibrary(const char *libname)
+{
+   fAutoLoadedLibraries.insert(libname);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 /// Register a new shared library name with the interpreter; add it to
 /// fSharedLibs.
@@ -6668,6 +6681,7 @@ void* TCling::LazyFunctionCreatorAutoload(const std::string& mangled_name) {
    if (!LibLoader(libName))
       return nullptr;
 
+   fAutoLoadedLibraries.insert(libName);
    return llvm::sys::DynamicLibrary::SearchForAddressOfSymbol(dlsym_mangled_name);
 }
 

core/metacling/src/TCling.h

@@ -122,6 +122,7 @@ class TCling final : public TInterpreter {
    std::set<size_t> fPayloads; // Set of payloads
    std::set<const char*> fParsedPayloadsAddresses; // Set of payloads which were parsed
    std::set<std::string> fAutoParseClasses; // Set of classes for which we autoparsed a header
+   std::set<std::string> fAutoLoadedLibraries; // Set of libraries that were autoloaded
    std::hash<std::string> fStringHashFunction; // A simple hashing function
    std::unordered_set<const clang::NamespaceDecl*> fNSFromRootmaps;   // Collection of namespaces fwd declared in the rootmaps
    TObjArray*      fRootmapFiles;     // Loaded rootmap files.
@@ -259,6 +260,8 @@ class TCling final : public TInterpreter {
    void    RegisterTClassUpdate(TClass *oldcl,DictFuncPtr_t dict) final;
    void    UnRegisterTClassUpdate(const TClass *oldcl) final;
 
+   void    RegisterAutoLoadedLibrary(const char *libname) final;
+
    Int_t   SetClassSharedLibs(const char *cls, const char *libs) final;
    void    SetGetline(const char * (*getlineFunc)(const char* prompt),
                       void (*histaddFunc)(const char* line)) final;