[clang] [clang][analyzer] Support `fputs` in the StreamChecker (PR #73335)

[Balázs Kéri via cfe-commits]

================
@@ -824,20 +817,76 @@ void StreamChecker::evalFgetcFputc(const FnDescription *Desc,
 
   // If a (non-EOF) error occurs, the resulting value of the file position
   // indicator for the stream is indeterminate.
-  StreamErrorState NewES;
-  if (IsRead)
-    NewES =
-        OldSS->ErrorState == ErrorFEof ? ErrorFEof : ErrorFEof | ErrorFError;
-  else
-    NewES = ErrorFError;
+  StreamErrorState NewES =
+      OldSS->ErrorState == ErrorFEof ? ErrorFEof : ErrorFEof | ErrorFError;
   StreamState NewSS = StreamState::getOpened(Desc, NewES, !NewES.isFEof());
   StateFailed = StateFailed->set<StreamMap>(StreamSym, NewSS);
-  if (IsRead && OldSS->ErrorState != ErrorFEof)
+  if (OldSS->ErrorState != ErrorFEof)
     C.addTransition(StateFailed, constructSetEofNoteTag(C, StreamSym));
   else
     C.addTransition(StateFailed);
 }
 
+void StreamChecker::evalFputx(const FnDescription *Desc, const CallEvent &Call,
+                              CheckerContext &C, bool IsSingleChar) const {
+  ProgramStateRef State = C.getState();
+  SymbolRef StreamSym = getStreamArg(Desc, Call).getAsSymbol();
+  if (!StreamSym)
+    return;
+
+  const CallExpr *CE = dyn_cast_or_null<CallExpr>(Call.getOriginExpr());
+  if (!CE)
+    return;
+
+  const StreamState *OldSS = State->get<StreamMap>(StreamSym);
+  if (!OldSS)
+    return;
+
+  assertStreamStateOpened(OldSS);
+
+  // `fputc` returns the written character on success, otherwise returns EOF.
+  // `fputs` returns a non negative value on sucecess, otherwise returns EOF.
+
+  // Generddate a transition for the success state of `fputc`.
+  if (IsSingleChar) {
+    std::optional<NonLoc> PutVal = Call.getArgSVal(0).getAs<NonLoc>();
+    if (!PutVal)
+      return;
+    ProgramStateRef StateNotFailed =
+        State->BindExpr(CE, C.getLocationContext(), *PutVal);
+    StateNotFailed =
+        StateNotFailed->set<StreamMap>(StreamSym, StreamState::getOpened(Desc));
+    C.addTransition(StateNotFailed);
+  }
+  // Generddate a transition for the success state of `fputs`.
+  else {
+    NonLoc RetVal = makeRetVal(C, CE).castAs<NonLoc>();
+    ProgramStateRef StateNotFailed =
+        State->BindExpr(CE, C.getLocationContext(), RetVal);
+    SValBuilder &SVB = C.getSValBuilder();
+    auto &ASTC = C.getASTContext();
----------------
balazske wrote:

Line 866 still contains `auto`, usually `auto` is not used at such places (https://llvm.org/docs/CodingStandards.html#id29).

https://github.com/llvm/llvm-project/pull/73335