[PATCH] D102273: [analyzer] LoopUnrolling: fix crash when a loop counter is captured in a lambda by reference
Abbas Sabra via Phabricator via cfe-commits
cfe-commits at lists.llvm.org
Fri May 14 10:07:24 PDT 2021
AbbasSabra added inline comments.
================
Comment at: clang/lib/StaticAnalyzer/Core/LoopUnrolling.cpp:185-186
+ return FD->getType()->isReferenceType();
+ } else {
+ assert(false && "Unknown captured variable");
+ }
----------------
vsavchenko wrote:
> AbbasSabra wrote:
> > vsavchenko wrote:
> > > But actually, it's a bit different with this one. I don't know exact details and rules how clang sema fills in the class for lambda.
> > > According to [[ https://en.cppreference.com/w/cpp/language/lambda | cppreference ]]:
> > > > For the entities that are captured by reference (with the default capture [&] or when using the character &, e.g. [&a, &b, &c]), it is unspecified if additional data members are declared in the closure type
> > >
> > > It can be pretty much specified in clang, that's true, but it looks like in `DeadStoreChecker` we have a very similar situation and we do not assume that captured variable always have a corresponding field.
> > Yes, I based this on the fact that DeadStoreChecker considers it possible, but I have never faced a case where it does not have a corresponding field.
> It still would be good to have some proof that it is indeed like this or simply fallback into returning true (which you already do when in doubt).
As I said, I believe it cannot happen but I assumed based on the other checker that there is something I don't know.
I think based on !!getCaptureFields!! the implementation we are iterating over all captures. For that algorithm to work number of captures should be equal to number of fields
```
void CXXRecordDecl::getCaptureFields(
llvm::DenseMap<const VarDecl *, FieldDecl *> &Captures,
FieldDecl *&ThisCapture) const {
Captures.clear();
ThisCapture = nullptr;
LambdaDefinitionData &Lambda = getLambdaData();
RecordDecl::field_iterator Field = field_begin();
for (const LambdaCapture *C = Lambda.Captures, *CEnd = C + Lambda.NumCaptures;
C != CEnd; ++C, ++Field) {
if (C->capturesThis())
ThisCapture = *Field;
else if (C->capturesVariable())
Captures[C->getCapturedVar()] = *Field;
}
assert(Field == field_end());
}
```
I dropped the defensive code
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D102273/new/
https://reviews.llvm.org/D102273
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