[clang] [clang][analyzer] fix false positive of BlockInCriticalSectionChecker (PR #126752)

[via cfe-commits]

================
@@ -339,6 +425,36 @@ void BlockInCriticalSectionChecker::reportBlockInCritSection(
                                                     os.str(), ErrNode);
   R->addRange(Call.getSourceRange());
   R->markInteresting(Call.getReturnValue());
+  // for 'read' call, check whether it's file descriptor(first argument) is
+  // created by 'open' API with O_NONBLOCK flag and don't report for this
+  // situation.
+  if (Call.getCalleeIdentifier()->getName() == "read") {
+    do {
+      const auto *arg = Call.getArgExpr(0);
+      if (!arg)
+        break;
+
+      const auto *DRE = dyn_cast<DeclRefExpr>(arg->IgnoreImpCasts());
----------------
flovent wrote:

i am hoping to get the MemRegion of file descriptor here and compare its corresponding SVal between pred node and current node in `VisitNode`, i can't use `getArgSVal` to get SVal as region because `open` call is evaluated to a symbol or int(-1).
is there a way to check binding from SVal to Expr?

https://github.com/llvm/llvm-project/pull/126752