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

[Alejandro Álvarez Ayllón via cfe-commits]

================
@@ -1158,6 +1173,118 @@ void StreamChecker::evalUngetc(const FnDescription *Desc, const CallEvent &Call,
   C.addTransition(StateFailed);
 }
 
+ProgramStateRef
+StreamChecker::ensurePtrNotNull(SVal PtrVal, const Expr *PtrExpr,
+                                CheckerContext &C, ProgramStateRef State,
+                                const StringRef PtrDescr) const {
+  const auto Ptr = PtrVal.getAs<DefinedSVal>();
+  if (!Ptr)
+    return nullptr;
+
+  assert(PtrExpr && "Expected an argument");
+
+  const auto [PtrNotNull, PtrNull] = State->assume(*Ptr);
+  if (!PtrNotNull && PtrNull) {
+    if (ExplodedNode *N = C.generateErrorNode(PtrNull)) {
+      auto R = std::make_unique<PathSensitiveBugReport>(
+          BT_SizeNull, (PtrDescr + " pointer might be NULL.").str(), N);
+      bugreporter::trackExpressionValue(N, PtrExpr, *R);
+      C.emitReport(std::move(R));
+    }
+    return nullptr;
+  }
+
+  return PtrNotNull;
+}
+
+ProgramStateRef StreamChecker::ensureSizeZeroIfLineNull(
+    SVal LinePtrPtrSVal, SVal SizePtrSVal, const Expr *LinePtrPtrExpr,
+    const Expr *SizePtrExpr, CheckerContext &C, ProgramStateRef State) const {
+  static constexpr char SizeNotZeroMsg[] =
+      "Line pointer might be null while n value is not zero";
+
+  // We have a pointer to a pointer to the buffer, and a pointer to the size.
+  // We want what they point at.
+  auto LinePtrSVal = getPointeeDefVal(LinePtrPtrSVal, State);
+  auto NSVal = getPointeeDefVal(SizePtrSVal, State);
+  if (!LinePtrSVal || !NSVal)
+    return nullptr;
+
+  assert(LinePtrPtrExpr &&
+         "Expected an argument with a pointer to a pointer to the buffer.");
+  assert(SizePtrExpr &&
+         "Expected an argument with a pointer to the buffer size.");
+
+  // If the line pointer is null, and n is > 0, there is UB.
+  const auto [LinePtrNotNull, LinePtrNull] = State->assume(*LinePtrSVal);
+  if (LinePtrNull && !LinePtrNotNull) {
+    const auto [NIsNotZero, NIsZero] = LinePtrNull->assume(*NSVal);
+    if (NIsNotZero && !NIsZero) {
+      if (ExplodedNode *N = C.generateErrorNode(NIsNotZero)) {
+        auto R = std::make_unique<PathSensitiveBugReport>(BT_SizeNotZero,
+                                                          SizeNotZeroMsg, N);
+        bugreporter::trackExpressionValue(N, SizePtrExpr, *R);
+        bugreporter::trackExpressionValue(N, LinePtrPtrExpr, *R);
+        C.emitReport(std::move(R));
+      }
+      return nullptr;
+    }
+    return NIsZero;
+  }
+  return LinePtrNotNull;
+}
+
+void StreamChecker::preGetdelim(const FnDescription *Desc,
+                                const CallEvent &Call,
+                                CheckerContext &C) const {
+  ProgramStateRef State = C.getState();
+  SVal StreamVal = getStreamArg(Desc, Call);
+
+  auto AddTransitionOnReturn = llvm::make_scope_exit([&] {
----------------
alejandro-alvarez-sonarsource wrote:

Indeed. This is a leftover from unrelated downstream changes. I have removed it.

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