[clang] [clang][analyzer] fix false positive of BlockInCriticalSectionChecker (PR #127049)

[Balazs Benics via cfe-commits]

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@@ -315,16 +342,54 @@ bool BlockInCriticalSectionChecker::isBlockingInCritSection(
 void BlockInCriticalSectionChecker::checkPostCall(const CallEvent &Call,
                                                   CheckerContext &C) const {
   if (isBlockingInCritSection(Call, C)) {
+    // 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") {
+      const auto *Arg = Call.getArgExpr(0);
+      if (!Arg)
+        return;
+
+      SVal SV = C.getSVal(Arg);
+      if (const auto *IntValue = SV.getAsInteger()) {
+        if (*IntValue == -1)
+          return;
+      }
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steakhal wrote:

Is this hunk relevant because we may have a perfectly constrained symbol for Arg, that itself is a symbol, but had a constraint for it that it must be equal to `-1`?
Is this scenario covered by tests?

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