xazax.hun added inline comments.
================
Comment at:
clang-tools-extra/clang-tidy/bugprone/UncheckedOptionalAccessCheck.cpp:84
+ if (!BlockToOutputState ||
+ BlockToOutputState->size() <= Context->getCFG().getExit().getBlockID())
+ return;
----------------
ymandel wrote:
> xazax.hun wrote:
> > xazax.hun wrote:
> > > ymandel wrote:
> > > > xazax.hun wrote:
> > > > > xazax.hun wrote:
> > > > > > Could the size of the vector ever be wrong? Should this be an
> > > > > > assert instead?
> > > > > Whoops, after the update this comment is out of place, now it
> > > > > supposed to be on line 60.
> > > > Based on my reading, it is a rare, but possible condition. Basically,
> > > > we need code where the exit block is unreachable, which I believe can
> > > > happen in weird cases like:
> > > >
> > > > ```
> > > > while(true) {...}
> > > > ```
> > > > https://godbolt.org/z/rfEnfaWTv -- notice the lack of predecessors for
> > > > the exit block.
> > > >
> > > > See the code here, which follows the ordering of the blocks and doesn't
> > > > force blocks to be processed:
> > > >
> > > > https://github.com/llvm/llvm-project/blob/main/clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp#L337-L364
> > > Interesting. Since we already have optionals in the vector, I assumed we
> > > will always have matching size. I think we might want to change this so
> > > there is only one way for the analysis to not provide a state for a basic
> > > block to make this a bit less confusing,
> > Actually, in the linked code I see `
> > BlockStates.resize(CFCtx.getCFG().size(), llvm::None);`. So I would expect
> > the size to be always right with possibly some `None`s for the nodes that
> > were not processed.
> > Actually, in the linked code I see `
> > BlockStates.resize(CFCtx.getCFG().size(), llvm::None);`. So I would expect
> > the size to be always right with possibly some `None`s for the nodes that
> > were not processed.
> Ah, my mistake! I thought `resize` only allocated the space. #TIL
>
> Changed to an assert. Thanks.
>
But this discussion shed light on an interesting detail. If the exit block is
unreachable, we will not diagnose the unsafe accesses. I wonder if this worth a
FIXME.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D121120/new/
https://reviews.llvm.org/D121120
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