[cfe-dev] using clang - getting type for C variable declaration

[David Blaikie]

On Fri, Nov 9, 2012 at 2:12 AM, Rajendra <rks at cse.iitb.ac.in> wrote:
> 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.

>     {
>       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 :) 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
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