如何从clang中的Expr *获取整数变量名称及其值 [英] how to get integer variable name and its value from Expr* in clang

问题描述

我在重写的方法中有以下代码 VisitBinaryOperator（） for clang：

  Expr * lhs = E-> getLHS（）; 
 Expr * rhs = E-> getRHS（）; 
 

我想从表达式中提取整数变量名称及其值 lhs 和 rhs 。


说我有 x = 10; ，那么我想获得标识符 x 从 lhs 和 10 code>。

如果我有 x = x + 10; 那么我想获得标识符 x lhs 和 x + 10 作为子表达式从 rhs

此外，当我转储：int identifier > lhs type

  QualType type_lhs = lhs-> getType（）; 
 type_lhs-> dump（）; 
  

如何为clang做到这一点？

  if（DeclRefExpr * DRE = dyn_cast< DeclRefExpr>（lhs））{
 //它是一个声明的引用... 
 if（VarDecl * VD = dyn_cast< VarDecl>（DRE-> getDecl（）））{
 //它是对变量（局部，函数参数，全局或静态数据成员）的引用。 
 std :: cout<< LHS是< VD-> getQualifiedNameAsString（）<< std :: endl; 
} 
} 
  

处理LHS上的其他表达式。如果要处理任意代码，请查看 RecursiveASTVisitor 。

要评估（假设它是Clang可以评估的东西，例如 10 ，不像 x + 10 ）， Expr 的之一函数

：

  llvm :: APSInt结果; 
 if（rhs-> EvaluateAsInt（Result，ASTContext））{
 std :: cout< RHS具有值< Result.toString（10）<< std :: endl; 
} 
  

I have following code in an overridden method VisitBinaryOperator() for clang:

Expr* lhs = E->getLHS();  
Expr* rhs = E->getRHS();  

I want to extract integer variable name and its value from expression lhs and rhs.

Say I have x = 10;, then I want to get identifier x from lhs and 10 from rhs.
If I have x = x + 10; then I want to get identifier x from lhs and x + 10 as sub expression from rhs

Also for type I am getting this : int identifier when I dump lhs type

QualType type_lhs = lhs->getType();  
type_lhs->dump();  

How this can be done for clang?

解决方案

Use dyn_cast to determine what kind of expression you have on the LHS:

if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(lhs)) {
  // It's a reference to a declaration...
  if (VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
    // It's a reference to a variable (a local, function parameter, global, or static data member).
     std::cout << "LHS is " << VD->getQualifiedNameAsString() << std::endl;
  }
}

You'll need more complex code if you want to handle other expression forms on the LHS. If you want to deal with arbitrary code there, take a look at RecursiveASTVisitor.

To evaluate the value of the right-hand side (assuming it's something that Clang can evaluate, like 10, not like x + 10), use one of Expr's Evaluate* functions:

llvm::APSInt Result;
if (rhs->EvaluateAsInt(Result, ASTContext)) {
  std::cout << "RHS has value " << Result.toString(10) << std::endl;
}

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