prepare for calling ParseAST. Fatal error

I'm reading the book Getting Started with LLVM Core Libraries and trying to implement an example from page 100 Chapter 4: Frontend. But got an error on the last line of code clang::ParseAST(CI.getSema());:

[bash@bash book]$ ./book_clang test.c 
fatal error: error opening file '<invalid loc>':

What should I add to prepare for ParseAST?

code:

#include "llvm/ADT/IntrusiveRefCntPtr.h"
#include "llvm/Support/CommandLine.h"

#include "clang/Basic/Diagnostic.h"

#include "clang/Frontend/CompilerInstance.h"

#include "clang/Basic/TargetInfo.h"
#include "clang/Basic/TargetOptions.h"

#include "llvm/Support/Host.h"
#include <memory>
#include <string>

#include "clang/Basic/FileManager.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Lex/PreprocessorOptions.h"
#include "clang/Lex/Preprocessor.h"

#include "clang/AST/ASTConsumer.h"
#include "clang/Frontend/ASTConsumers.h"

#include "llvm/Support/raw_ostream.h"

#include "clang/Parse/ParseAST.h"

#include "clang/AST/ASTContext.h"


static llvm::cl::opt<std::string> fileName(llvm::cl::Positional, llvm::cl::desc("Input file"), llvm::cl::Required);

int main(int argc, char **argv)
{
    llvm::cl::ParseCommandLineOptions(argc, argv, "My simple front end\n");
    clang::CompilerInstance CI;
    clang::DiagnosticOptions diagnosticOptions;
    CI.createDiagnostics();

    std::shared_ptr<clang::TargetOptions> PTO = std::make_shared<clang::TargetOptions>();
    PTO->Triple = llvm::sys::getDefaultTargetTriple();
    clang::TargetInfo *PTI = clang::TargetInfo::CreateTargetInfo(CI.getDiagnostics(), PTO);
    CI.setTarget(PTI);

    CI.createFileManager();//References getFileSystemOpts(), clang::vfs::getRealFileSystem(), hasVirtualFileSystem(), and setVirtualFileSystem().
    CI.createSourceManager( CI.getFileManager());//References getDiagnostics().
    CI.createPreprocessor(clang::TU_Complete);
    CI.getPreprocessorOpts().UsePredefines = false;

    std::unique_ptr< clang::ASTConsumer > astConsumer = clang::CreateASTPrinter(NULL, "");
    CI.setASTConsumer(std::move(astConsumer));

    CI.createASTContext();
    CI.createSema(clang::TU_Complete, NULL);//after getASTConsumer(), getASTContext(), and getPreprocessor().
    const clang::FileEntry *file =    CI.getFileManager().getFile(fileName);
    if (!file) {
        llvm::errs() << "File not found: " << fileName;
        return 1;
    }
    CI.getSourceManager().createFileID(file, clang::SourceLocation(), clang::SrcMgr::C_User);


    CI.getDiagnosticClient().BeginSourceFile(CI.getLangOpts(), 0);
    clang::ParseAST(CI.getSema());
    // Print AST statistics
//   CI.getASTContext().PrintStats();
//  CI.getASTContext().Idents.PrintStats();

    return 0;
}

for executable need to pass c-file, for example: test.c

int main() {
char *msg = "Hello, world!\n";
write(1, msg, 14);
return 0;
}

Solution

the problem is solved. Need to set MainFileID for CompilerInstence's SourceManager

clang::FileID mainFileID = CI.getSourceManager().createFileID(file,    clang::SourceLocation(), clang::SrcMgr::C_User);
CI.getSourceManager().setMainFileID(mainFileID);

The problem was that clang::ParseAST calls (S is Sema) S.getPreprocessor().EnterMainSourceFile(); that calls SourceMgr.getMainFileID();

void Preprocessor::EnterMainSourceFile() {
assert(NumEnteredSourceFiles == 0 && "Cannot reenter the main file!");
FileID MainFileID = SourceMgr.getMainFileID();

But MainFileID was'n set

corrected full code is:

#include "llvm/Support/CommandLine.h"

#include "clang/Basic/Diagnostic.h"

#include "clang/Frontend/CompilerInstance.h"

#include "clang/Basic/TargetInfo.h"
#include "clang/Basic/TargetOptions.h"

#include "llvm/Support/Host.h"
#include <memory>
#include <string>

#include "clang/Basic/FileManager.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Lex/PreprocessorOptions.h"
#include "clang/Lex/Preprocessor.h"

#include "clang/AST/ASTConsumer.h"
#include "clang/Frontend/ASTConsumers.h"

#include "llvm/Support/raw_ostream.h"

#include "clang/Parse/ParseAST.h"

#include "clang/AST/ASTContext.h"


static llvm::cl::opt<std::string> fileName(llvm::cl::Positional, llvm::cl::desc("Input file"), llvm::cl::Required);

int main(int argc, char **argv)
{      
    llvm::cl::ParseCommandLineOptions(argc, argv, "My simple front end\n");

    clang::CompilerInstance CI;
    clang::DiagnosticOptions diagnosticOptions;
    CI.createDiagnostics();

    std::shared_ptr<clang::TargetOptions> PTO = std::make_shared<clang::TargetOptions>();
    PTO->Triple = llvm::sys::getDefaultTargetTriple();
    clang::TargetInfo *PTI = clang::TargetInfo::CreateTargetInfo(CI.getDiagnostics(), PTO);
    CI.setTarget(PTI);

    CI.createFileManager();//References getFileSystemOpts(), clang::vfs::getRealFileSystem(), hasVirtualFileSystem(), and setVirtualFileSystem().
    CI.createSourceManager( CI.getFileManager());//References getDiagnostics().
    CI.createPreprocessor(clang::TU_Complete);
    CI.getPreprocessorOpts().UsePredefines = false;

    std::unique_ptr< clang::ASTConsumer > astConsumer = clang::CreateASTPrinter(NULL, "");
    CI.setASTConsumer(std::move(astConsumer));

    CI.createASTContext();
    CI.createSema(clang::TU_Complete, NULL);//after getASTConsumer(), getASTContext(), and getPreprocessor().
    const clang::FileEntry *file = CI.getFileManager().getFile(fileName);
    if (!file) {
            llvm::errs() << "File not found: " << fileName;
            return 1;
    }
    clang::FileID mainFileID = CI.getSourceManager().createFileID(file, clang::SourceLocation(), clang::SrcMgr::C_User);
    CI.getSourceManager().setMainFileID(mainFileID);


    CI.getDiagnosticClient().BeginSourceFile(CI.getLangOpts(), 0);
    clang::ParseAST(CI.getSema());
    // Print AST statistics
    CI.getASTContext().PrintStats();
    CI.getASTContext().Idents.PrintStats();

    return 0;
}