Traverse AST

Hi all,

I’m using clang AST to do some static analysis.
In my case, I want to find all assignment statements for pointer variables.
For example, here is the source code snippet:
int *a, int **b;
**b = *a;
I want to know there is an assignment from “*a” to “**b”.

I use RecursiveASTVistor to traverse AST. I rewrite VistitStmt() to check if AST Node is an assignment statement.

bool VisitStmt(Stmt *s) {

if(BinaryOperator *binaryOperator = dyn_cast(s)) {

if(binaryOperator->isAssignmentOp()) { do something}


Here is the AST for the source code snippet above:

BinaryOperator 0x9532d48 <line:66:2, col:14> ‘int’ ‘=’

-UnaryOperator 0x9532cb0 <col:2, col:4> ‘int’ lvalue prefix ‘*’

`-ImplicitCastExpr 0x9532c98 <col:3, col:4> ‘int *’

`-UnaryOperator 0x9532c78 <col:3, col:4> ‘int ’ lvalue prefix '

`-ImplicitCastExpr 0x9532c60 col:4 ‘int **’

`-DeclRefExpr 0x9532c38 col:4 ‘int **’ lvalue Var 0x9532b00 ‘b’ ‘int **’

`-ImplicitCastExpr 0x9532d30 <col:13, col:14> ‘int’

`-UnaryOperator 0x9532d10 <col:13, col:14> ‘int’ lvalue prefix ‘*’

`-ImplicitCastExpr 0x9532cf8 col:14 ‘int *’

`-DeclRefExpr 0x9532cd0 col:14 ‘int *’ lvalue Var 0x9532a88 ‘a’ ‘int *’

In VisitStmt() function, at the point when this BinaryOperator is visited, I only have the information of the current AST Node.
How can I traverse the subtree of this BinaryOperator so that I can get all the info, such as variable name a, b, prefix * ,** ?

Thank you.

You can call BinaryOperator::getLHS() and BinaryOperator::getRHS() and
use the results to manually visit the left- and right-hand sides of
the operator. However, for your use case the ASTMatchers interface may
be a better approach -- see the documentation here:

You could use a matcher like this:

  auto hasPointerType = ...; // not sure exactly what you want here
  binaryOperator(hasOperatorName("="), hasLHS(hasPointerType),