ymandel added inline comments.
================ Comment at: clang/unittests/Analysis/FlowSensitive/TransferTest.cpp:1551-1552 + const Value *FooVal = Env.getValue(*FooLoc); + // TODO: Initialise values inside unions, then change below to + // ASSERT_TRUE. + ASSERT_FALSE(isa_and_nonnull<IntegerValue>(FooVal)); ---------------- merrymeerkat wrote: > ymandel wrote: > > merrymeerkat wrote: > > > ymandel wrote: > > > > Why push this off to another patch? > > > good point! I was pushing it because this is just a quick fix to avoid a > > > crash, and the current changes are sufficient for that > > SGTM. Please use FIXME instead of TODO, though. But, glad to see this is > > enough to avoid the crashing! > > > > That said, can you expand on where the actual crash was happening? I'm > > concerned that its possible that the crash site should be more robust and > > that this patch is hiding that weakness. > Done! > > The crash was happening because of a null pointer cast in the builtin > transfer function for CFGInitializers: > https://github.com/llvm/llvm-project/blob/781eabeb40b8e47e3a46b0b927784e63f0aad9ab/clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp#L316 > > Hmm so do you think it'd be helpful to add a null check in the file above? Thanks, that's quite helpful! Yes, I think that would be a better fix. It's a matter of perspective (and opinion) so feel free to push back but I'd say that the code you pointed to is buggy -- it assumes the `this` loc is populated, but *by design* it's not populated for unions (I didn't know that unions could ever have `this` so #TIL?). I think we're admitting that we have a class of initializers for which we knowingly don't create the this pointer and therefore should express that in the code. Alternatively, you could argue that the complete class of `this` pointer generating code is structs and unions, so if we just make sure (like your fix) to generate a this pointer in both cases, we can assert it's non-nullness (via the cast) and be done. Given that the framework in general is riddled with places where we don't know if a value or storage location or... is initialized and we have to check, I think that's the better (and consistent) approach. Moreover, given that we're not actually adding support for unions, just trying to avoid a crash, I think changing that code site better expresses that intent. Still, it's a matter of opinion, so I'll leave it to you to decide. WDYT? Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D140696/new/ https://reviews.llvm.org/D140696 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
