[Rcpp-devel] Call to function through pointer to incorrect function type on UBSAN

[Kevin Ushey]

I can't replicate the reported UBSAN issues on my macOS machine (R-devel
compiled with LLVM clang 4.0.1, with address + undefined behavior
sanitizers active).

The warnings look somewhat dubious to me: for example, the first warning:

function_pointers.h:99:12: runtime error: call to function
a1_fn(arma::Col<double> const&, arma::Col<double> const&) through
pointer to incorrect function type 'arma::Col<double> (*)(const
arma::Col<double> &, const arma::Col<double> &)'
/tmp/RtmpObvRHm/sourceCpp-x86_64-pc-linux-gnu-0.12.11/sourcecpp_96075e756157/growth_model_functions.cpp:7:
note: a1_fn(arma::Col<double> const&, arma::Col<double> const&)
defined here

If I'm reading that correctly, you have the following types:

Pointer:                      (arma::Col<double> const&,
arma::Col<double> const& )
Actual:  arma::Col<double> (*)(const arma::Col<double> &, const
arma::Col<double> &)

and those look compatible to me (the only difference is the ordering of the
'const &' printing in each case).

Unless I'm missing something obvious, it seems like this might just be a
bug in the version of UBSAN used on the CRAN build machines? The fact that
this error is not seen with gcc, only with clang, supports that hypothesis,
so I think you can safely ignore those errors. (Perhaps this was a bug in
Clang 4.0.0 that was fixed in Clang 4.0.1)

Kevin


On Fri, Jul 7, 2017 at 2:58 PM, Helske, Jouni <jouni.helske at jyu.fi> wrote:

> I got some warnings on CRAN with UBSAN relating to my use of user supplied
> C++ function using Xptr: https://www.stats.ox.ac.uk/
> pub/bdr/memtests/clang-UBSAN/bssm/build_vignettes.log
>
> I can't see anything wrong in my codes, although I have just tried to
> mimic some Dirk's Xptr examples without fully understanding what is going
> on, so maybe I actually do something silly. But I then noticed that Rcpp
> also has similar kind of warnings (https://www.stats.ox.ac.uk/
> pub/bdr/memtests/clang-UBSAN/Rcpp/build_vignettes.log), so I wonder if
> these are anything to worry about? I tested my package on GCC based address
> sanitizer using docker, and did not get any warnings with that setup, which
> makes me think that maybe it's just some clang issue? Some googling seems
> to support this theory: https://stackoverflow.com/
> questions/43220926/call-to-function-unknown-through-
> pointer-to-incorrect-function-type
>
> Best,
>
> Jouni
>
>
>
>
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