Abort on R type error if debugging

[jackwasey]

Following discussion in #857 , this PR prints an error to standard error, and aborts, allowing a debugger to examine state leading up to the error, instead of dropping out of R. The assert macro didn't seem like the right tool, as it would never give an informative error message. The glibc assert macro calls abort, so I used it here, while checking for absence ofNDEBUG. The default build process in R is done with -DNDEBUG so this should not alter behavior for anyone who hasn't explicitly used -UNDEBUG, and therefore this should not impact any packages built for CRAN in the usual way.

There is no obvious way for me to add an automated test for this code, since it requires compiling with and without the NDEBUG flag set.

[kevinushey]

#else instead of #elif?

[jackwasey]

Yes... whoops. But it worked with clang, so I missed it.

[codecov-io]

Codecov Report

Merging #860 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master    #860   +/-   ##
======================================
  Coverage    90.3%   90.3%           
======================================
  Files          70      70           
  Lines        3261    3261           
======================================
  Hits         2945    2945           
  Misses        316     316

Impacted Files	Coverage Δ
inst/include/Rcpp/r_cast.h	100% <ø> (ø)	⬆️

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[eddelbuettel]

Should that not be REprintf() ?

[jackwasey]

I wasn't aware of REprintf, made the change.

I used the following to test:

Rcpp::cppFunction('void type_err(IntegerVector iv) {}')
type_err("a")

Which aborts with the appropriate error message if I add -UNDEBUG in CXXFLAGS before compilation, otherwise gives normal Rcpp behavior.

[eddelbuettel]

Thanks. REprintf() is one of those gems hidden away in WRE which "they" to nag you on submission. You know, like 'no stdout, no abort, ...' ;-)