aaron.ballman added inline comments.
================ Comment at: clang/include/clang/AST/Stmt.h:596-597 - // These don't need to be particularly wide, because they're - // strictly limited by the forms of expressions we permit. - unsigned NumSubExprs : 8; - unsigned ResultIndex : 32 - 8 - NumExprBits; + unsigned NumSubExprs : 16; + unsigned ResultIndex : 16; }; ---------------- yronglin wrote: > dblaikie wrote: > > dblaikie wrote: > > > aaron.ballman wrote: > > > > dblaikie wrote: > > > > > Could/should we add some error checking in the ctor to assert that we > > > > > don't overflow these longer values/just hit the bug later on? > > > > > > > > > > (& could we use `unsigned short` here rather than bitfields?) > > > > We've already got them packed in with other bit-fields from the > > > > expression bits, so I think it's reasonable to continue the pattern of > > > > using bit-fields (that way we don't accidentally end up with padding > > > > between the unnamed bits at the start and the named bits in this > > > > object). > > > > > > > > I think adding some assertions would not be a bad idea as a follow-up. > > > Maybe some unconditional (rather than only in asserts builds) error > > > handling? (report_fatal_error, if this is low priority enough to not have > > > an elegant failure mode, but something where we don't just overflow and > > > carry on would be good... ) > > Ping on this? I worry this code has just punted the same bug further down, > > but not plugged the hole/ensured we don't overflow on novel/larger inputs. > Sorry for the late reply, I was looking through the emails and found this. I > agree add some assertions to check the value is a good idea, It's easy to > help people catch bugs, at least with when `-DLLVM_ENABLE_ASSERTIONS=ON`, and > I'm glad to work on it, but one thing that worries me is that, in ASTReader, > we access this field directly, not through the constructor or accessor, and > we have to add assertions everywhere. > https://github.com/llvm/llvm-project/blob/05b4310c8aec7a050574277ced08a0ab86b27681/clang/lib/Serialization/ASTReaderStmt.cpp#L1382 I don't think we have to add too many assertions. As best I can tell, we'll need one in each of the `PseudoObjectExpr` constructors and one in `ASTStmtReader::VisitPseudoObjectExpr()`, but those are the only places we assign a value into the bit-field. Three assertions isn't a lot, but if we're worried, we could add a setter method that does the assertion and use the setter in all three places. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D154784/new/ https://reviews.llvm.org/D154784 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
