[cfe-dev] clang dump openmp node

Xiaohui Chen xchen422 at uwo.ca
Tue Dec 2 16:42:16 PST 2014


i wonder that whether it is possible to restore the preprocessed tokens when 
i output the AST.

for example, this is the input file:

#define COND

void test(int var)
{
#ifdef COND
 var = 1;
#else
 var = 2;
#endif
}

when the parser builds the AST, we will lose some parts of the code,
so is it possible to output the AST which is the same with the input? 



On 12/01/14, Nikola Smiljanic  <popizdeh at gmail.com> wrote:
> AFAIK OpenMP is still work in progress... Hope Alexey knows more about this.
> 
> On Tue, Dec 2, 2014 at 5:26 AM, Xiaohui Chen <xchen422 at uwo.ca> wrote:
> 
> > hi  Nikola:
> > i can not dump the openmp node, am i missing some options?
> > for example:
> > 
> > int main()
> > {
> > int k=90, l=0;
> > #pragma omp parallel private(k, l)
> > {
> >  #pragma omp for
> >  for(int kk=0; kk<90;kk++)
> >  {
> >  l;
> >  }
> > }
> > }
> > 
> > I use the following command to compile:
> > 
> > clang++ -Xclang -ast-dump -Xclang -fopenmp=libiomp5 t.cpp
> > 
> > output is :
> > 
> > `-OMPParallelDirective 0x6febf50 <line:32:9, col:35>
> >  `-CapturedStmt 0x6febf10 <line:33:1, line:39:1>
> >  `-DeclRefExpr 0x6feb7f8 <line:37:3> 'int' lvalue Var 0x6fe8590 'l' 'int'
> > 
> > it did not say anything about the for loop and the private clause.
> > 
> > Sincerely
> > xiaohui
> > 
> > On 11/23/14, Nikola Smiljanic  <popizdeh at gmail.com> wrote:
> > > Yes, and it'll call cc1_main.
> > > 
> > > On Mon, Nov 24, 2014 at 4:17 PM, Xiaohui Chen <xchen422 at uwo.ca> wrote:
> > > 
> > > > yes, you are right. Usually i just use the frontend through -cc1, and now i want to know a little about the workflow of the driver .
> > > > 
> > > > so does this mean that the frontend and driver shares the same main() function as i said below?
> > > > because i notice that in line 412 of main() function it will check the -cc1 flag.
> > > > 
> > > > 
> > > > On 11/23/14, Nikola Smiljanic  <popizdeh at gmail.com> wrote:
> > > > > When you invoke something like "clang test.cpp -o test" you're invoking the driver. It will process the options you passed to it and build a list of arguments to pass to the frontend and other tools (assembler, linker, etc.). It will spawn a new process for the frontend. 
> > > > > 
> > > > > 
> > > > > To see the arguments passed to the frontend use -###.
> > > > > To invoke the frontend directly use -cc1. If you're interested in clang's lexing/parsing/sema logic using someting like "clang -cc1 -fsyntax-only test.cpp" should be enough.
> > > > > 
> > > > > 
> > > > > On Mon, Nov 24, 2014 at 3:38 PM, Xiaohui Chen <xchen422 at uwo.ca> wrote:
> > > > > 
> > > > > > hi all:
> > > > > > 
> > > > > > i am looking into the "main function" of llvm/tools/clang/tools/driver/driver.cpp,
> > > > > > i only add several llvm::outs() in the source code, and re-compile the source code again,
> > > > > > then i use the clang to compile my input file(t.c) like this:
> > > > > > 
> > > > > > xchen422 at dimsum:~$ clang t.c
> > > > > > 
> > > > > >  the output is :
> > > > > > 
> > > > > > xchen422 at dimsum:~$ clang t.c 
> > > > > > clang main function start point 1
> > > > > > clang main function start point 3
> > > > > > clang main function start point 4
> > > > > > clang main function start point 1
> > > > > > clang main function start point 2
> > > > > > clang main function start point 5
> > > > > > clang main function start point 6
> > > > > > xchen422 at dimsum:~$ 
> > > > > > 
> > > > > > It seems that the main() function is called twice, also it seems that there are 
> > > > > > some magic in this function(line 468):
> > > > > >  Res = TheDriver.ExecuteCompilation(*C, FailingCommands);
> > > > > > 
> > > > > > i could not understand, could someone give me a brief explanation. 
> > > > > > 
> > > > > > 
> > > > > > PS:
> > > > > > 1). I add llvm::outs() in line 379, line 418, line 422, line 466, line 470 and line 512.
> > > > > > 2). t.c file only contains an empty main() function.
> > > > > > 3). i paste the main() function below.
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > >  int main(int argc_, const char **argv_) {
> > > > > > 379 llvm::outs() << "clang main function start point 1" << '\n';
> > > > > > 380 
> > > > > > 381 
> > > > > > 382 llvm::sys::PrintStackTraceOnErrorSignal();
> > > > > > 383 llvm::PrettyStackTraceProgram X(argc_, argv_);
> > > > > > 384 
> > > > > > 385 if (llvm::sys::Process::FixupStandardFileDescriptors())
> > > > > > 386 return 1;
> > > > > > 387 
> > > > > > 388 SmallVector<const char *, 256> argv;
> > > > > > 389 llvm::SpecificBumpPtrAllocator<char> ArgAllocator;
> > > > > > 390 std::error_code EC = llvm::sys::Process::GetArgumentVector(
> > > > > > 391 argv, llvm::makeArrayRef(argv_, argc_), ArgAllocator);
> > > > > > 392 if (EC) {
> > > > > > 393 llvm::errs() << "error: couldn't get arguments: " << EC.message() << '\n';
> > > > > > 394 return 1;
> > > > > > 395 }
> > > > > > 396 
> > > > > > 397 std::set<std::string> SavedStrings;
> > > > > > 398 StringSetSaver Saver(SavedStrings);
> > > > > > 399 
> > > > > > 400 // Determines whether we want nullptr markers in argv to indicate response
> > > > > > 401 // files end-of-lines. We only use this for the /LINK driver argument.
> > > > > > 402 bool MarkEOLs = true;
> > > > > > 403 if (argv.size() > 1 && StringRef(argv[1]).startswith("-cc1"))
> > > > > > 404 MarkEOLs = false;
> > > > > > 405 llvm::cl::ExpandResponseFiles(Saver, llvm::cl::TokenizeGNUCommandLine, argv,
> > > > > > 406 MarkEOLs);
> > > > > > 407 
> > > > > > 408 // Handle -cc1 integrated tools, even if -cc1 was expanded from a response
> > > > > > 409 // file.
> > > > > > 410 auto FirstArg = std::find_if(argv.begin() + 1, argv.end(),
> > > > > > 411 [](const char *A) { return A != nullptr; });
> > > > > > 412 if (FirstArg != argv.end() && StringRef(*FirstArg).startswith("-cc1")) {
> > > > > > 413 // If -cc1 came from a response file, remove the EOL sentinels.
> > > > > > 414 if (MarkEOLs) {
> > > > > > 415 auto newEnd = std::remove(argv.begin(), argv.end(), nullptr);
> > > > > > 416 argv.resize(newEnd - argv.begin());
> > > > > > 417 }
> > > > > > 418 llvm::outs() << "clang main function start point 2" << '\n';
> > > > > > 419 return ExecuteCC1Tool(argv, argv[1] + 4);
> > > > > > 420 }
> > > > > > 421 
> > > > > > 422 llvm::outs() << "clang main function start point 3" << '\n';
> > > > > > 423 bool CanonicalPrefixes = true;
> > > > > > 424 for (int i = 1, size = argv.size(); i < size; ++i) {
> > > > > > 425 // Skip end-of-line response file markers
> > > > > > 426 if (argv[i] == nullptr)
> > > > > > 427 continue;
> > > > > > 428 if (StringRef(argv[i]) == "-no-canonical-prefixes") {
> > > > > > 429 CanonicalPrefixes = false;
> > > > > > 430 break;
> > > > > > 431 }
> > > > > > 432 }
> > > > > > 433 
> > > > > > 434 // Handle CCC_OVERRIDE_OPTIONS, used for editing a command line behind the
> > > > > > 435 // scenes.
> > > > > > 436 if (const char *OverrideStr = ::getenv("CCC_OVERRIDE_OPTIONS")) {
> > > > > > 437 // FIXME: Driver shouldn't take extra initial argument.
> > > > > > 438 ApplyQAOverride(argv, OverrideStr, SavedStrings);
> > > > > > 439 }
> > > > > > 440 
> > > > > > 441 std::string Path = GetExecutablePath(argv[0], CanonicalPrefixes);
> > > > > > 442 
> > > > > > 443 IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts =
> > > > > > 444 CreateAndPopulateDiagOpts(argv);
> > > > > > 445 
> > > > > > 446 TextDiagnosticPrinter *DiagClient
> > > > > > 447 = new TextDiagnosticPrinter(llvm::errs(), &*DiagOpts);
> > > > > > 448 FixupDiagPrefixExeName(DiagClient, Path);
> > > > > > 449 
> > > > > > 450 IntrusiveRefCntPtr<DiagnosticIDs> DiagID(new DiagnosticIDs());
> > > > > > 451 
> > > > > > 452 DiagnosticsEngine Diags(DiagID, &*DiagOpts, DiagClient);
> > > > > > 453 ProcessWarningOptions(Diags, *DiagOpts, /*ReportDiags=*/false);
> > > > > > 454 
> > > > > > 455 Driver TheDriver(Path, llvm::sys::getDefaultTargetTriple(), Diags);
> > > > > > 456 SetInstallDir(argv, TheDriver);
> > > > > > 457 
> > > > > > 458 llvm::InitializeAllTargets();
> > > > > > 459 ParseProgName(argv, SavedStrings);
> > > > > > 460 
> > > > > > 461 SetBackdoorDriverOutputsFromEnvVars(TheDriver);
> > > > > > 462 
> > > > > > 463 std::unique_ptr<Compilation> C(TheDriver.BuildCompilation(argv));
> > > > > > 464 int Res = 0;
> > > > > > 465 SmallVector<std::pair<int, const Command *>, 4> FailingCommands;
> > > > > > 466 llvm::outs() << "clang main function start point 4" << '\n';
> > > > > > 467 if (C.get())
> > > > > > 468 Res = TheDriver.ExecuteCompilation(*C, FailingCommands);
> > > > > > 469 
> > > > > > 470 llvm::outs() << "clang main function start point 5" << '\n';
> > > > > > 471 // Force a crash to test the diagnostics.
> > > > > > 472 if (::getenv("FORCE_CLANG_DIAGNOSTICS_CRASH")) {
> > > > > > 473 Diags.Report(diag::err_drv_force_crash) << "FORCE_CLANG_DIAGNOSTICS_CRASH";
> > > > > > 474 const Command *FailingCommand = nullptr;
> > > > > > 475 FailingCommands.push_back(std::make_pair(-1, FailingCommand));
> > > > > > 476 }
> > > > > > 477 
> > > > > > 478 for (const auto &P : FailingCommands) {
> > > > > > 479 int CommandRes = P.first;
> > > > > > 480 const Command *FailingCommand = P.second;
> > > > > > 481 if (!Res)
> > > > > > 482 Res = CommandRes;
> > > > > > 483 
> > > > > > 484 // If result status is < 0, then the driver command signalled an error.
> > > > > > 485 // If result status is 70, then the driver command reported a fatal error.
> > > > > > 486 // On Windows, abort will return an exit code of 3. In these cases,
> > > > > > 487 // generate additional diagnostic information if possible.
> > > > > > 488 bool DiagnoseCrash = CommandRes < 0 || CommandRes == 70;
> > > > > > 489 #ifdef LLVM_ON_WIN32
> > > > > > 490 DiagnoseCrash |= CommandRes == 3;
> > > > > > 491 #endif
> > > > > > 492 if (DiagnoseCrash) {
> > > > > > 493 TheDriver.generateCompilationDiagnostics(*C, FailingCommand);
> > > > > > 494 break;
> > > > > > 495 }
> > > > > > 496 }
> > > > > > 497 
> > > > > > 498 // If any timers were active but haven't been destroyed yet, print their
> > > > > > 499 // results now. This happens in -disable-free mode.
> > > > > > 500 llvm::TimerGroup::printAll(llvm::errs());
> > > > > > 501 
> > > > > > 502 llvm::llvm_shutdown();
> > > > > > 503 
> > > > > > 504 #ifdef LLVM_ON_WIN32
> > > > > > 505 // Exit status should not be negative on Win32, unless abnormal termination.
> > > > > > 506 // Once abnormal termiation was caught, negative status should not be
> > > > > > 507 // propagated.
> > > > > > 508 if (Res < 0)
> > > > > > 509 Res = 1;
> > > > > > 510 #endif
> > > > > > 511 
> > > > > > 512 llvm::outs() << "clang main function start point 6" << '\n';
> > > > > > 513 // If we have multiple failing commands, we return the result of the first
> > > > > > 514 // failing command.
> > > > > > 515 return Res;
> > > > > > 516 }
> > > > > >  
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > On 11/06/14, Nikola Smiljanic  <popizdeh at gmail.com> wrote:
> > > > > > > I'm not sure how long make takes to run if there's nothing to compile. But you should definitely check out cmake + ninja.
> > > > > > > 
> > > > > > > On Fri, Nov 7, 2014 at 10:52 AM, Xiaohui Chen <xchen422 at uwo.ca> wrote:
> > > > > > > 
> > > > > > > > yes, i know, the makefile will skip compiling the code if i do not change them, but it will still 
> > > > > > > > go through some directories and say "nothing to do" i guess.
> > > > > > > > 
> > > > > > > > it is ok, i can use the current solution. Thank you!
> > > > > > > > 
> > > > > > > > On 11/06/14, Nikola Smiljanic  <popizdeh at gmail.com> wrote:
> > > > > > > > > How will it waste time if you don't change it?
> > > > > > > > > 
> > > > > > > > > On Fri, Nov 7, 2014 at 9:53 AM, Xiaohui Chen <xchen422 at uwo.ca> wrote:
> > > > > > > > > 
> > > > > > > > > > I am writing a source to source tool which need to add some new keywords in the clang source file, so this tool can parse 
> > > > > > > > > > the input file with my new keywords, now this tool is still under developing and debugging, each time when i want to 
> > > > > > > > > > recompile this tool i do not want to involve llvm stuff, because it will waste some time......
> > > > > > > > > > 
> > > > > > > > > > On 11/06/14, Nikola Smiljanic  <popizdeh at gmail.com> wrote:
> > > > > > > > > > > Why exactly do you want an out of source build if your using makefiles? It's beneficial with Visual Studio but I don't see the reason for it if you're building from the command line?
> > > > > > > > > > > 
> > > > > > > > > > > On Fri, Nov 7, 2014 at 9:14 AM, Xiaohui Chen <xchen422 at uwo.ca> wrote:
> > > > > > > > > > > 
> > > > > > > > > > > > .... i have no idea of cmake ....
> > > > > > > > > > > > 
> > > > > > > > > > > > i use makefile under linux, so who could help?
> > > > > > > > > > > > 
> > > > > > > > > > > > On 11/06/14, Nikola Smiljanic  <popizdeh at gmail.com> wrote:
> > > > > > > > > > > > > I only know how to do this with cmake.
> > > > > > > > > > > > > 
> > > > > > > > > > > > > On Fri, Nov 7, 2014 at 8:32 AM, Xiaohui Chen <xchen422 at uwo.ca> wrote:
> > > > > > > > > > > > > 
> > > > > > > > > > > > > > i think i get your point and that is what i expect.
> > > > > > > > > > > > > > 
> > > > > > > > > > > > > > you mean that:
> > > > > > > > > > > > > > 
> > > > > > > > > > > > > > 1. make a standalone directory for Clang not in llvm/tools
> > > > > > > > > > > > > > 
> > > > > > > > > > > > > > 2. compile both llvm and clang as usual
> > > > > > > > > > > > > > 
> > > > > > > > > > > > > > 3. if i modify Clang source file, i just execute the Makefile inside clang/ directory, so it
> > > > > > > > > > > > > > will just re-compile the Clang file without checking llvm files
> > > > > > > > > > > > > > 
> > > > > > > > > > > > > > is there any instructions to do this? 
> > > > > > > > > > > > > > 
> > > > > > > > > > > > > > Especially in step 2, if i compile in this way i guess i will break the dependence relationship in "configure" file?
> > > > > > > > > > > > > > 
> > > > > > > > > > > > > > Best 
> > > > > > > > > > > > > > xiaohui
> > > > > > > > > > > > > > 
> > > > > > > > > > > > > > On 11/06/14, Nikola Smiljanic  <popizdeh at gmail.com> wrote:
> > > > > > > > > > > > > > > The best you can do is compile clang "out of source". Meaning the clang directory stands on its own and not in llvm/projects. This makes a difference if you're generating Visual Studio solution file as you won't have to load llvm projects. But llvm must be built.
> > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > On Fri, Nov 7, 2014 at 4:24 AM, Jingyue Wu <jingyue at google.com> wrote:
> > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > I don't think so. clang uses a lot of LLVM's core libraries. 
> > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > Jingyue
> > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > On Thu Nov 06 2014 at 9:14:49 AM Xiaohui Chen <xchen422 at uwo.ca> wrote:
> > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > Hi all:
> > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > I am writing a source to source tool and adding new keywords in the clang source file(i just care about the AST), 
> > > > > > > > > > > > > > > > > is there a way to just compile the clang frontend source file but not including llvm source file?
> > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > Sincerely
> > > > > > > > > > > > > > > > > xiaohui 
> > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > On 11/03/14, Nikola Smiljanic  <popizdeh at gmail.com> wrote:
> > > > > > > > > > > > > > > > > > On Tue, Nov 4, 2014 at 7:14 AM, Xiaohui Chen <xchen422 at uwo.ca> wrote:
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > Thanks for your reply.
> > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > I am confusing here:
> > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > 1. Traverse method visits AST nodes that form a tree. CXXRecordDecl is the parent of each of its CXXMethodDecls and FieldDecls.
> > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > >  CXXMethodDecls ( FieldDecls ) is not a member of CXXRecordDecl and also does not inherit from CXXRecordDecl, so how could
> > > > > > > > > > > > > > > > > > > you define them as parent-child relationship?
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > CXXRecordDecl contains CXXMethodDecls and RecordDecl contains FieldDecls. They're just stored in the DeclContext class but are exposed with method_begin/method_end and field_begin/field_end.
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > 2. WalkUpFrom method visits the class hierarchy of a single AST node. CXXRecordDecl inherits RecordDecl which inherits TagDecl etc.
> > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > here TagDecl has three direct parents, so will WalkUpFrom be applied to these three classes?
> > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > TagDecl does have three super classes but only one of them is also an AST node. AST is built from declarations, statements and types. DeclContext represents a declaration context and structs/classes introduce one. They are also redeclarable (forward declaration) which is what Redeclarable class keeps track of.
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > sincerely
> > > > > > > > > > > > > > > > > > > xiaohui
> > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > On 11/03/14, Nikola Smiljanic  <popizdeh at gmail.com> wrote:
> > > > > > > > > > > > > > > > > > > > There are two parent-child relationships at play.
> > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > 1. Traverse method visits AST nodes that form a tree. CXXRecordDecl is the parent of each of its CXXMethodDecls and FieldDecls. This is what you'll see with clang -cc1 -ast-dump
> > > > > > > > > > > > > > > > > > > > 2. WalkUpFrom method visits the class hierarchy of a single AST node. CXXRecordDecl inherits RecordDecl which inherits TagDecl etc. Think of serialization, to serialize CXXRecordDecl you'd first want to serialize everything from the base class and so on recursively.
> > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > On Mon, Nov 3, 2014 at 12:32 PM, Xiaohui Chen <xchen422 at uwo.ca> wrote:
> > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > >  Dear all:
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > I am using Clang as the frontend of my project, but i am confusing of the following statements.
> > > > > > > > > > > > > > > > > > > > > PS: i am a newbie. 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > These tasks are done by three groups of methods, respectively: 00089 /// 1. TraverseDecl(Decl *x) does task #1. It is the entry point 00090 /// for traversing an AST rooted at x. This method simply 00091 /// dispatches (i.e. forwards) to TraverseFoo(Foo *x) where Foo 00092 /// is the dynamic type of *x, which calls WalkUpFromFoo(x) and 00093 /// then recursively visits the child nodes of x. 00094 /// TraverseStmt(Stmt *x) and TraverseType(QualType x) work 00095 /// similarly. 00096 /// 2. WalkUpFromFoo(Foo *x) does task #2. It does not try to visit 00097 /// any child node of x. Instead, it first calls WalkUpFromBar(x) 00098 /// where Bar is the direct parent class of Foo (unless Foo has 00099 /// no parent), and then calls VisitFoo(x) (see the next list item). 00100 /// 3. VisitFoo(Foo *x) does task #3. 00101 /// 00102 /// These three method groups are tiered (Traverse* > WalkUpFrom* > 00103 /// Visit*). A method (e.g. Traverse*) may call methods from the same 00104 /// tier (e.g. other Traverse*) or one tier lower (e.g. WalkUpFrom*). 00105 /// It may not call methods from a higher tier.
> > > > > > > > > > > > > > > > > > > > > According to the above statement, the calling relationship between these
> > > > > > > > > > > > > > > > > > > > > functions are organized in this way in general:
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > Traversal*()
> > > > > > > > > > > > > > > > > > > > > {
> > > > > > > > > > > > > > > > > > > > >  .......
> > > > > > > > > > > > > > > > > > > > >  WalkUpFrom*();
> > > > > > > > > > > > > > > > > > > > >  .......
> > > > > > > > > > > > > > > > > > > > > }
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > WalkUpFrom*()
> > > > > > > > > > > > > > > > > > > > > {
> > > > > > > > > > > > > > > > > > > > >  .......
> > > > > > > > > > > > > > > > > > > > >  Visit*();
> > > > > > > > > > > > > > > > > > > > >  .......
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > }
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > am i right?
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > For this statement:
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 00096 /// 2. WalkUpFromFoo(Foo *x) does task #2. It does not try to visit 00097 /// any child node of x. Instead, it first calls WalkUpFromBar(x) 00098 /// where Bar is the direct parent class of Foo (unless Foo has 00099 /// no parent), and then calls VisitFoo(x) (see the next list item).
> > > > > > > > > > > > > > > > > > > > > what do you mean by saying "the direct parent class of Foo"?
> > > > > > > > > > > > > > > > > > > > > why i need to visit the parent class before i visit the current class? 
> > > > > > > > > > > > > > > > > > > > > what is the purpose? Could you please give me a short example?
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > Thank you in advance!
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > Sincerely
> > > > > > > > > > > > > > > > > > > > > xiaohui
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > >  
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > _______________________________________________
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > cfe-dev mailing list
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > cfe-dev at cs.uiuc.edu
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > >  
> > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > >  
> > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > >  
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > _______________________________________________
> > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > cfe-dev mailing list
> > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > cfe-dev at cs.uiuc.edu
> > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
> > > > > > > > > > > > > > > > >  
> > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > >  
> > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > _______________________________________________
> > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > cfe-dev mailing list
> > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > cfe-dev at cs.uiuc.edu
> > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
> > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > 
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> > > > > 
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> > > > 
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> > > 
> > > 
> > > 
> > >  
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> >  
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