IMHO, this should be changed in both Rcpp and downstream packages: 1. Rcpp could check for out-of-bounds accesses in cases like these, and emit an R warning / error when such an access is detected;
2. The downstream packages unintentionally making these out-of-bounds accesses should be fixed to avoid doing that. That is, I think this is ultimately a bug in the affected packages, but Rcpp could do better in detecting and handling this for client packages (avoiding a segfault). Best, Kevin On Sat, Jun 8, 2024, 3:06 PM Ben Bolker <bbol...@gmail.com> wrote: > > A change to R-devel (SVN r86629 or > > https://github.com/r-devel/r-svn/commit/92c1d5de23c93576f55062e26d446feface07250 > has changed the handling of pointers to zero-length objects, leading to > ASAN issues with a number of Rcpp-based packages (the commit message > reads, in part, "Also define STRICT_TYPECHECK when compiling inlined.c.") > > I'm interested in discussion from the community. > > Details/diagnosis for the issues in the lme4 package are here: > https://github.com/lme4/lme4/issues/794, with a bit more discussion > about how zero-length objects should be handled. > > The short(ish) version is that r86629 enables the > CATCH_ZERO_LENGTH_ACCESS definition. This turns on the CHKZLN macro > < > https://github.com/r-devel/r-svn/blob/4ef83b9dc3c6874e774195d329cbb6c11a71c414/src/main/memory.c#L4090-L4104>, > > which returns a trivial pointer (rather than the data pointer that would > be returned in the normal control flow) if an object has length 0: > > /* Attempts to read or write elements of a zero length vector will > result in a segfault, rather than read and write random memory. > Returning NULL would be more natural, but Matrix seems to assume > that even zero-length vectors have non-NULL data pointers, so > return (void *) 1 instead. Zero-length CHARSXP objects still have a > trailing zero byte so they are not handled. */ > > In the Rcpp context this leads to an inconsistency, where `REAL(x)` > is a 'real' external pointer and `DATAPTR(x)` is 0x1, which in turn > leads to ASAN warnings like > > runtime error: reference binding to misaligned address 0x000000000001 > for type 'const double', which requires 8 byte alignment > 0x000000000001: note: pointer points here > > I'm in over my head and hoping for insight into whether this problem > should be resolved by changing R, Rcpp, or downstream Rcpp packages ... > > cheers > Ben Bolker > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > [[alternative HTML version deleted]] ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
