Traces external pointers in parenthesized expressions

Partially reverts 80667b7, "Fix unary operator handling of probe
reads with parens", keeping the test case. With 4c6ecb4,
"Restrict rewrite of unary operators to dereference operator," only
dereferences are rewritten, removing the need for the previous fix.

Reverting 80667b7 allows bcc to rewrite more dereferences, as
highlighted in the new test case.

src/cc/frontends/clang/b_frontend_action.cc

@@ -83,9 +83,6 @@ class ProbeChecker : public RecursiveASTVisitor<ProbeChecker> {
  }
  return false;
  }
- bool VisitParenExpr(ParenExpr *E) {
- return false;
- }
  bool VisitDeclRefExpr(DeclRefExpr *E) {
  if (ptregs_.find(E->getDecl()) != ptregs_.end())
  needs_probe_ = true;

tests/python/test_clang.py

@@ -349,6 +349,17 @@ def test_unop_probe_read(self):
  return 1;
  return 0;
 }
+"""
+ b = BPF(text=text)
+ fn = b.load_func("trace_entry", BPF.KPROBE)
+
+ def test_paren_probe_read(self):
+ text = """
+#include <net/inet_sock.h>
+int trace_entry(struct pt_regs *ctx, struct sock *sk) {
+ u16 sport = ((struct inet_sock *)sk)->inet_sport;
+ return sport;
+}
 """
  b = BPF(text=text)
  fn = b.load_func("trace_entry", BPF.KPROBE)