RCPP_CTOR_ASSIGN compiler warning in Rcpp/Module.h

[jpritikin]

I might be able to figure out the cause of this warning, but you could probably figure it out much faster.

/opt/R/x86_64-pc-linux-gnu-library/3.2/Rcpp/include/Rcpp/Module.h: In copy constructor ‘Rcpp::CppClass::CppClass(const Rcpp::CppClass&)’:
/opt/R/x86_64-pc-linux-gnu-library/3.2/Rcpp/include/Rcpp/Module.h:404:23: warning: base class ‘class Rcpp::S4_Impl<Rcpp::PreserveStorage>’ should be explicitly initialized in the copy constructor [-Wextra]
      RCPP_CTOR_ASSIGN(CppClass)
                       ^
/opt/R/x86_64-pc-linux-gnu-library/3.2/Rcpp/include/Rcpp/macros/interface.h:27:1: note: in definition of macro ‘RCPP_CTOR_ASSIGN’
 __CLASS__( const __CLASS__& other ){                                           \
 ^
/opt/R/x86_64-pc-linux-gnu-library/3.2/Rcpp/include/Rcpp/Module.h: In copy constructor ‘Rcpp::CppObject::CppObject(const Rcpp::CppObject&)’:
/opt/R/x86_64-pc-linux-gnu-library/3.2/Rcpp/include/Rcpp/Module.h:416:26: warning: base class ‘class Rcpp::S4_Impl<Rcpp::PreserveStorage>’ should be explicitly initialized in the copy constructor [-Wextra]
         RCPP_CTOR_ASSIGN(CppObject)
                          ^
/opt/R/x86_64-pc-linux-gnu-library/3.2/Rcpp/include/Rcpp/macros/interface.h:27:1: note: in definition of macro ‘RCPP_CTOR_ASSIGN’
 __CLASS__( const __CLASS__& other ){                                           \
 ^

[eddelbuettel]

1. Complete reproducible example, please, or it is no bug report or issue.
2. What compiler? What OS? What version of things?
3. Just add -Wno-extra to your compiler options to suppress this. It is a warning.

[jpritikin]

Rcpp 0.12.2, R 3.2.2, gcc (Tanglu 5.2.1-16) 5.2.1 20150903

[eddelbuettel]

g++-5 is known to be pickier. Pull requests welcome.

[jpritikin]

I'm willing to spend some time to investigate. Can you give me a hint about what to fix?

[eddelbuettel]

Really appreciate this -- the 90k lines of code for Rcpp can be very convoluted and tough to decipher. I'd start by seeing what RCPP_CTOR_ASSIGN is made of and the try to find the copy constructor this warns about.

[jpritikin]

The warning is solved by changing this,

#define RCPP_CTOR_ASSIGN1(__CLASS__)                                           \
__CLASS__( const __CLASS__& other ){                                           \
    Storage::copy__(other) ;                                                   \
}                                                                              \

to this

#define RCPP_CTOR_ASSIGN(__CLASS__)                                            \
  __CLASS__( const __CLASS__& other ) : Base(other) {           \
    Storage::copy__(other) ;                                                   \
}                                                                              \

However, this requires (for the macro) that there is only 1 base class. For users of RCPP_GENERATE_CTOR_ASSIGN, the change is not needed. So maybe the way forward is to create 2 versions of RCPP_CTOR_ASSIGN, one with the Base(other) thing and one without.

Comments?

[eddelbuettel]

In that case we would need two distinct versions of RCPP_CTOR_ASSIGN as you can't have two with the same name; maybe keep the existing one as RCPP_CTOR_ASSIGN_ORIG or something. We could even flag it to be deprecated in 12+ months. All this assuming that reverse depends check don't reveal anything nasty.

[jpritikin]

Hm, it's it redundant to initialize the base class and also do Storage::copy__ ?

[eddelbuettel]

This can be closed as @thirdwing reminds us.