Implement the autoloading for ROOT_MODULES.

git-svn-id: http://root.cern.ch/svn/root/trunk@48385 27541ba8-7e3a-0410-8455-c3a389f83636

include/cling/Interpreter/Interpreter.h

@@ -449,6 +449,16 @@ namespace cling {
     ///
     CompilationResult parse(const std::string& input);
 
+    ///\brief Looks for a already generated PCM for the given header file and 
+    /// loads it.
+    ///
+    ///\param[in] headerFile - The header file for which a module should be 
+    ///                        loaded.
+    ///
+    ///\returns Whether the operation was fully successful.
+    ///
+    CompilationResult loadModuleForHeader(const std::string& headerFile);
+
     ///\brief Parses input line, which doesn't contain statements. Code 
     /// generation needed to make the module functional.
     ///

lib/Interpreter/Interpreter.cpp

@@ -402,6 +402,38 @@ namespace cling {
     return DeclareInternal(input, CO);
   }
 
+  Interpreter::CompilationResult
+  Interpreter::loadModuleForHeader(const std::string& headerFile) {
+    Preprocessor& PP = getCI()->getPreprocessor();
+    //Copied from clang's PPDirectives.cpp
+    bool isAngled = false;
+    // Clang doc says:
+    // "LookupFrom is set when this is a \#include_next directive, it specifies 
+    // the file to start searching from."
+    const DirectoryLookup* LookupFrom = 0;
+    const DirectoryLookup* CurDir = 0;
+
+    Module* module = 0;
+    const FileEntry *file = PP.LookupFile(headerFile, isAngled, LookupFrom,
+                                          CurDir, /*SearchPath*/0,
+                                          /*RelativePath*/ 0, &module, 
+                                          /*SkipCache*/false);
+    if (!module)
+      return Interpreter::kFailure;
+
+    SourceLocation fileNameLoc;
+    ModuleIdPath path = std::make_pair(PP.getIdentifierInfo(module->Name),
+                                       fileNameLoc);
+
+    SourceLocation includeLoc;
+    Module* imported = getCI()->loadModule(includeLoc, path, Module::AllVisible,
+                                           /*isIncludeDirective*/true);
+    if (imported)
+      return Interpreter::kSuccess;
+
+    return Interpreter::kFailure;
+  }
+
   Interpreter::CompilationResult
   Interpreter::parseForModule(const std::string& input) {
     CompilationOptions CO;