================
@@ -2122,8 +2122,21 @@ SVal
RegionStoreManager::getBindingForField(RegionBindingsConstRef B,
if (const std::optional<SVal> &V = B.getDirectBinding(R))
return *V;
- // If the containing record was initialized, try to get its constant value.
+ // UnnamedBitField is always Undefined unless using memory operation such
+ // as 'memset'.
+ // For example, for code
+ // typedef struct {
+ // int i :2;
+ // int :30; // unnamed bit-field
+ // } A;
+ // A a = {1};
+ // The bits of the unnamed bit-field in local variable a can be anything.
const FieldDecl *FD = R->getDecl();
+ if (FD->isUnnamedBitField()) {
+ return UndefinedVal();
+ }
+
+ // If the containing record was initialized, try to get its constant value.
----------------
Tedlion wrote:
To solve the false warning problem with unnamed bit-field, patch here is
unnecessary.
However, I do not think `getBinding` returning `SymbolVal` is the correct
result, which is the current behavior when parsing the source as c++. To my
understanding, `SymbolVal` means it is initialized, but somehow the static
analyzer cannot infer the value, while `UndefinedVal` means the value it stores
can be anything and reading from it is an UB. Unnamed bit-field is the second
case.
I understand patching here may bring influences to other usages, even though
the test of check-clang-analysis does not show any. So if you think that
current implementation is incorrect but we'd better keep it before fully
evaluating the influences, let me leave a FIXME comment here.
https://github.com/llvm/llvm-project/pull/145066
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