[clang] [clang][analyzer] Fix incorrect range of 'ftell' in the StdLibraryFunctionsChecker (PR #77576)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Ben Shi (benshi001)

<details>
<summary>Changes</summary>

According to https://pubs.opengroup.org/onlinepubs/9699919799/, the return value of 'ftell' is not restricted to > 0, and may return 0 in real world.

And the corresponding unit test also show `Ret >= 0` not `Ret > 0`.

https://github.com/llvm/llvm-project/blob/main/clang/test/Analysis/stream-errno.c#L194

---
Full diff: https://github.com/llvm/llvm-project/pull/77576.diff


1 Files Affected:

- (modified) clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp (+1-1) 


``````````diff
diff --git a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
index 32a2deab871c79..3b36565681a7f3 100644
--- a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
@@ -2274,7 +2274,7 @@ void StdLibraryFunctionsChecker::initFunctionSummaries(
     addToFunctionSummaryMap(
         "ftell", Signature(ArgTypes{FilePtrTy}, RetType{LongTy}),
         Summary(NoEvalCall)
-            .Case({ReturnValueCondition(WithinRange, Range(1, LongMax))},
+            .Case({ReturnValueCondition(WithinRange, Range(0, LongMax))},
                   ErrnoUnchanged, GenericSuccessMsg)
             .Case(ReturnsMinusOne, ErrnoNEZeroIrrelevant, GenericFailureMsg)
             .ArgConstraint(NotNull(ArgNo(0))));

``````````

</details>


https://github.com/llvm/llvm-project/pull/77576