[clang] [clang][analyzer] Model more getline/getdelim pre and postconditions (PR #83027)

[Alejandro Álvarez Ayllón via cfe-commits]

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@@ -1183,6 +1315,20 @@ void StreamChecker::evalGetdelim(const FnDescription *Desc,
         State->BindExpr(E.CE, C.getLocationContext(), RetVal);
     StateNotFailed =
         E.assumeBinOpNN(StateNotFailed, BO_GE, RetVal, E.getZeroVal(Call));
+    // The buffer size `*n` must be enough to hold the whole line, and
+    // greater than the return value, since it has to account for '\0'.
+    auto SizePtrSval = Call.getArgSVal(1);
+    auto NVal = getPointeeDefVal(SizePtrSval, State);
+    if (NVal) {
+      StateNotFailed = StateNotFailed->assume(
+          E.SVB
+              .evalBinOp(StateNotFailed, BinaryOperator::Opcode::BO_GT, *NVal,
+                         RetVal, E.SVB.getConditionType())
+              .castAs<DefinedOrUnknownSVal>(),
+          true);
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alejandro-alvarez-sonarsource wrote:

It doesn't, since the `n` got invalidated first. Anyway, I have added two more tests. 

https://github.com/llvm/llvm-project/pull/83027