[clang][analyzer][NFC] Supplement comments in evalFtell of StreamChecker

[benshi001]

No description provided.

[llvmbot]

@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-static-analyzer-1

Author: Ben Shi (benshi001)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/74291.diff

1 Files Affected:

• (modified) clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp (+3)

diff --git a/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
index a4799b5f762ca..925fc90e35543 100644
--- a/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
@@ -1072,6 +1072,9 @@ void StreamChecker::evalFtell(const FnDescription *Desc, const CallEvent &Call,
   ProgramStateRef StateFailed = State->BindExpr(
       CE, C.getLocationContext(), SVB.makeIntVal(-1, C.getASTContext().LongTy));
 
+  // This function does not affect the stream state.
+  // Still we add success and failure state with the appropriate return value.
+  // StdLibraryFunctionsChecker can change these states (set the 'errno' state).
   C.addTransition(StateNotFailed);
   C.addTransition(StateFailed);
 }