using clang - getting type for C variable declaration

Clang Frontend
#1

Hi,

1) I need to get type as string from Expr object. Any pointers?

   Expr* lhs = E->getLHS();

   if (strcmp(lhs->getStmtClassName(), "DeclRefExpr") == 0)
   {
     // get name and type for Expr *lhs from DeclRefExpr
     const DeclRefExpr *declRefExpr = dyn_cast<DeclRefExpr>(lhs);

     const ValueDecl *valueDecl = declRefExpr->getDecl();

     if (valueDecl)
     {
       std::cerr << "\tLHS identifier = " << valueDecl->getNameAsString() << "\n"; // this gives x

       QualType declQT = valueDecl->getType();
       std::cerr << "\tqual type: ";
       declQT.dump(); // this prints : int identifier

       // now call QualType.getAsString(PrintingPolicy &Policy)
       // ---> how to get compiler instance and AST context? <---- //
       clang::ASTContext &context = compilerInstance_ptr->getASTContext();
       std::cerr << "\ttype: " << declQT.getAsString(context.getPrintingPolicy()) << "\n";
     }
   }

2) Here is how I got things right for Decl :slight_smile: this will be helpful for others as well.

   clang::DeclGroupRef::iterator it;

   for (it = declGroupRef.begin(); it != declGroupRef.end(); it++)
   {
     clang::Decl* decl = *it;

     const NamedDecl *namedDecl = dyn_cast<NamedDecl>(decl);

     if (namedDecl)
     {
       std::cerr << "\tidentifier name = "
         << namedDecl->getNameAsString() << "\n";
     }

     const ValueDecl *valueDecl = dyn_cast<ValueDecl>(decl);

     if (valueDecl)
     {
       QualType declQT = valueDecl->getType();

       // now call QualType.getAsString(PrintingPolicy &Policy)
       clang::ASTContext &context = decl->getASTContext();
       std::cerr << "\ttype = " << declQT.getAsString(context.getPrintingPolicy()) << "\n";
     }
   }

Rajendra

#2

Hi,

1) I need to get type as string from Expr object. Any pointers?

Presumably Expr::getType():
http://clang.llvm.org/doxygen/classclang_1_1Expr.html#a3dd8850a4ad8a5b5f595dd9e9446187b

  Expr* lhs = E->getLHS();

  if (strcmp(lhs->getStmtClassName(), "DeclRefExpr") == 0)
  {
    // get name and type for Expr *lhs from DeclRefExpr
    const DeclRefExpr *declRefExpr = dyn_cast<DeclRefExpr>(lhs);

The usual way we write these last two lines is:

if (const DeclRefExpr *declRefExpr = dyn_cast<DeclRefExpr(lhs))

no string comparison required
no double-check (the string check and then the check in the dyn_cast)

For more details on LLVM's casting machinery:
http://llvm.org/docs/ProgrammersManual.html#isa

    const ValueDecl *valueDecl = declRefExpr->getDecl();

    if (valueDecl)

Just a stylistic point related to my first (in case you're planning to
be a Clang/LLVM contributor): we usually collapse the variable
declaration into the condition.

#3

Hi,

Actually, my question is more about getting type as string from Expr or QualType.

Say I have,
       QualType declQT = valueDecl->getType();
or
       QualType lhsQT = lhs->getType(); // lhs is on Expr* type

Now, I want to call QualType.getAsString(PrintingPolicy &Policy) and I need compiler instance or AST context to get printing policy, how to get compiler instance or AST context here?
       //compilerInstance_ptr?
       clang::ASTContext &context = compilerInstance_ptr->getASTContext();
       std::cerr << "\ttype: " << declQT.getAsString(context.getPrintingPolicy()) << "\n";

Using Decl, I could do this like decl->getASTContext(); - but same I cannot do here!

I am overriding method bool VisitBinAssign(BinaryOperator *E);

Rajendra

#4

Hi,

Actually, my question is more about getting type as string from Expr or
QualType.

Say I have,

      QualType declQT = valueDecl->getType();
or
      QualType lhsQT = lhs->getType(); // lhs is on Expr* type

Now, I want to call QualType.getAsString(PrintingPolicy &Policy) and I need
compiler instance or AST context to get printing policy, how to get compiler
instance or AST context here?
      //compilerInstance_ptr?

      clang::ASTContext &context = compilerInstance_ptr->getASTContext();
      std::cerr << "\ttype: " <<
declQT.getAsString(context.getPrintingPolicy()) << "\n";

Using Decl, I could do this like decl->getASTContext(); - but same I cannot
do here!

Off-hand, the simplest way I could find to do this was to look at how
QualType's dump() member is implemented:

It simply create a PrintingPolicy directly with a default LangOptions
( http://clang.llvm.org/doxygen/classclang_1_1QualType.html#a83734a19d59252c9527473a32cb44a12
). This may suffice for your needs. Otherwise I assume there's some
way to get the current ASTContext in your visitor, or perhaps track it
separately.