Add Expression::resolve string set

Adding Expression::resolve string unordered set to
keep a list of strings that need to be resolved.

It will be used in following patches as a list
to resolve with BTF data.

It's static set so it's cleared in the Driver
constructor, which is the starting point for
parsing.

src/ast/ast.cpp

@@ -5,6 +5,11 @@
 namespace bpftrace {
 namespace ast {
 
+std::unordered_set<std::string>& Expression::getResolve() {
+  static std::unordered_set<std::string> s;
+  return s;
+}
+
 void Integer::accept(Visitor &v) {
   v.visit(*this);
 }

src/ast/ast.h

@@ -5,6 +5,7 @@
 #include <map>
 #include <string>
 #include <vector>
+#include <unordered_set>
 
 #include "types.h"
 
@@ -34,6 +35,7 @@ class Expression : public Node {
   bool is_map = false;
   Expression() : Node(){};
   Expression(location loc) : Node(loc){};
+  static std::unordered_set<std::string>& getResolve();
 };
 using ExpressionList = std::vector<Expression *>;
 
@@ -86,12 +88,22 @@ class Identifier : public Expression {
 
 class Builtin : public Expression {
 public:
-  explicit Builtin(std::string ident) : ident(is_deprecated(ident)) {}
-  explicit Builtin(std::string ident, location loc) : Expression(loc), ident(is_deprecated(ident)) {}
+  explicit Builtin(std::string ident) : ident(is_deprecated(ident)) {
+    resolve_curtask(ident);
+  }
+  explicit Builtin(std::string ident, location loc) : Expression(loc), ident(is_deprecated(ident)) {
+    resolve_curtask(ident);
+  }
   std::string ident;
   int probe_id;
 
   void accept(Visitor &v) override;
+
+private:
+  void resolve_curtask(std::string& ident) {
+    if (ident == "curtask")
+      getResolve().insert("task_struct");
+  }
 };
 
 class Call : public Expression {
@@ -174,9 +186,13 @@ class ArrayAccess : public Expression {
 class Cast : public Expression {
 public:
   Cast(const std::string &type, bool is_pointer, Expression *expr)
-    : cast_type(type), is_pointer(is_pointer), expr(expr) { }
+    : cast_type(type), is_pointer(is_pointer), expr(expr) {
+    getResolve().insert(type);
+  }
   Cast(const std::string &type, bool is_pointer, Expression *expr, location loc)
-    : Expression(loc), cast_type(type), is_pointer(is_pointer), expr(expr) { }
+    : Expression(loc), cast_type(type), is_pointer(is_pointer), expr(expr) {
+    getResolve().insert(type);
+  }
   std::string cast_type;
   bool is_pointer;
   Expression *expr;

src/driver.cpp

@@ -13,6 +13,7 @@ namespace bpftrace {
 
 Driver::Driver(BPFtrace &bpftrace, std::ostream &o) : bpftrace_(bpftrace), out_(o)
 {
+  ast::Expression::getResolve().clear();
   yylex_init(&scanner_);
   parser_ = std::make_unique<Parser>(*this, scanner_);
 }