[clang] [clang][analyzer] Teach the BlockInCriticalSectionChecker about O_NONBLOCK streams (PR #127049)

[Gábor Horváth via cfe-commits]

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@@ -337,6 +391,28 @@ void BlockInCriticalSectionChecker::reportBlockInCritSection(
      << "' inside of critical section";
   auto R = std::make_unique<PathSensitiveBugReport>(BlockInCritSectionBugType,
                                                     os.str(), ErrNode);
+  // for 'read' and 'recv' call, check whether it's file descriptor(first
+  // argument) is
+  // created by 'open' API with O_NONBLOCK flag or is equal to -1, they will
+  // not cause block in these situations, don't report
+  StringRef FuncName = Call.getCalleeIdentifier()->getName();
+  if (FuncName == "read" || FuncName == "recv") {
+    SVal SV = Call.getArgSVal(0);
+    SValBuilder &SVB = C.getSValBuilder();
+    ProgramStateRef state = C.getState();
+    ConditionTruthVal CTV =
+        state->areEqual(SV, SVB.makeIntVal(-1, C.getASTContext().IntTy));
+    if (CTV.isConstrainedTrue())
+      return;
+
+    if (SymbolRef SR = SV.getAsSymbol()) {
+      if (!O_NONBLOCKValue)
+        O_NONBLOCKValue = tryExpandAsInteger(
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Xazax-hun wrote:

Why happens when `tryExpandAsInteger` fails? Would we unwrap an empty option below? I think we should be prepared for this failure case as users might not include the header containing the macro (but forward declare some functions themselves) or do other funky things and expect it to work. 

https://github.com/llvm/llvm-project/pull/127049