[clang][analyzer] Add function 'ungetc' to StreamChecker. (#77331)

`StdLibraryFunctionsChecker` is updated too with `ungetc`.

1 files changed, 19 insertions, 0 deletions

diff --git a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
index 034825d..32a2dea 100644
--- a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
@@ -2201,6 +2201,25 @@ void StdLibraryFunctionsChecker::initFunctionSummaries(
                   ErrnoNEZeroIrrelevant, GenericFailureMsg)
             .ArgConstraint(NotNull(ArgNo(0))));
 
+    // int ungetc(int c, FILE *stream);
+    addToFunctionSummaryMap(
+        "ungetc", Signature(ArgTypes{IntTy, FilePtrTy}, RetType{IntTy}),
+        Summary(NoEvalCall)
+            .Case({ReturnValueCondition(BO_EQ, ArgNo(0)),
+                   ArgumentCondition(0, WithinRange, {{0, UCharRangeMax}})},
+                  ErrnoMustNotBeChecked, GenericSuccessMsg)
+            .Case({ReturnValueCondition(WithinRange, SingleValue(EOFv)),
+                   ArgumentCondition(0, WithinRange, {{EOFv, EOFv}})},
+                  ErrnoNEZeroIrrelevant,
+                  "Assuming that 'ungetc' fails because EOF was passed as "
+                  "character")
+            .Case({ReturnValueCondition(WithinRange, SingleValue(EOFv)),
+                   ArgumentCondition(0, WithinRange, {{0, UCharRangeMax}})},
+                  ErrnoNEZeroIrrelevant, GenericFailureMsg)
+            .ArgConstraint(ArgumentCondition(
+                0, WithinRange, {{EOFv, EOFv}, {0, UCharRangeMax}}))
+            .ArgConstraint(NotNull(ArgNo(1))));
+
     // int fseek(FILE *stream, long offset, int whence);
     // FIXME: It can be possible to get the 'SEEK_' values (like EOFv) and use
     // these for condition of arg 2.