Signed/unsigned comparison in IndexHash

[Bijaelo]

This is a reboot of an old issue from 2016 #574, that seems to be present once again while compiling under windows. The compiler throws a warning after compiling the below code. Assume the below minimum reproducible example is located in the working directory in a file called test.cpp. Calling sourceCpp("test.cpp") results in a warning.

Snippet from the warning:

C:/Users/olive/Documents/R/win-library/4.0/Rcpp/include/Rcpp/hash/IndexHash.h:103:35: warning: comparison of integer expressions of different signedness: 'unsigned int' and 'int' [-Wsign-compare].

Session info included at the very bottom.

#include <Rcpp.h>
using namespace Rcpp;

inline bool allin(const SEXP& x, const SEXP& table){
  if(TYPEOF(x) != TYPEOF(table))
    stop("x and table must be of the same type.");
  switch(TYPEOF(x)){
    case INTSXP:
      return is_true(all(Rcpp::in(Vector<INTSXP>(x), Vector<INTSXP>(table))));
    case REALSXP:
      return is_true(all(Rcpp::in(Vector<REALSXP>(x), Vector<REALSXP>(table))));
    case STRSXP:
      return is_true(all(Rcpp::in(Vector<STRSXP>(x), Vector<STRSXP>(table))));
    default:
      stop("Invalid type in allin [Type = %s, valid = (%s, %s, %s)]",
           Rf_type2char(TYPEOF(x)),
           Rf_type2char(INTSXP),
           Rf_type2char(REALSXP),
           Rf_type2char(STRSXP));
  }
}

// [[Rcpp::export]]
void testStuff(const SEXP& x, const SEXP& table){
  Rcout << allin(x, table) << '\n';
}

/***R
# Example call: Unnessary for the issue
x <- 1:6
table <- 1:20
testStuff(x, table) 
*/

>sessionInfo()
R version 4.0.3 (2020-10-10)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 19042)

Matrix products: default

locale:
[1] LC_COLLATE=English_Denmark.1252  LC_CTYPE=English_Denmark.1252    LC_MONETARY=English_Denmark.1252 LC_NUMERIC=C                     LC_TIME=English_Denmark.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] Rcpp_1.0.6

loaded via a namespace (and not attached):
[1] compiler_4.0.3 tools_4.0.3  

[eddelbuettel]

( Not fully complete reproducible example as you did not include a trivial call to testStuff with data of your choosing. )

[Bijaelo]

Oh but to reproduce the "warning" no call to the function itself should be necessary. I am getting it when I compile through sourceCpp or alternatively build the package containing the function. So if you want a "full" reproducible example the only lacking piece should be library(Rcpp). :-)

[eddelbuettel]

(I understand that. I already reproduced it. I still ask you to add an example call so that everybody has the same run-time experience.)

I assume you are also aware of how to add flags such as Wno-sign-compare to the different CXX*FLAGS in ~/.R/Makevars? We covered that a few times here.

[Bijaelo]

Of course, thank you however. I mostly placed this report as it seemed to be a regression from the #574 (which was apparently fixed?). In practice it is only a nuisance.

[eddelbuettel]

Which is why it is not worth a) filing an issue (it is merely a warning) but if one insists as you do it is double foolish to do 95% of the work of an MCVE only to fail to add a call. But the worst is then to argue with me here 😁 instead of just saying "ah, yes" and editing the post.

[eddelbuettel]

You can carry the one-line fix over from 6a9ecc1.

(That comment was left pending for a few hours.)

[eddelbuettel]

What I meant with callable example was that you did already really well with the C++ snippet above, Just add this at the end

/*** R
x <- 1:6
table <- 1:20
testStuff(x, table) 
*/

which then gets autocalled when you sourceCpp() reducing your R code above to

library(Rcpp)
sourceCpp(...)

which is really Rcpp::sourceCpp(...) and implicit 😀 But the /*** R .... */ is pure gold. In case you didn't know.

[Bijaelo]

True, I didn't think of inlining the code into the Cpp snippet. I don't really use that feature day to day. 😀

And thanks for the quick fix. I've cloned it, as I'm likely doomed to forget setting the flags once in a while (and I prefer to stay out of Makeconf). 😁
Ps. I am from Denmark, so any comment left hanging may potentially be caused by the time difference. ☺️

[eddelbuettel]

and I prefer to stay out of Makeconf

Don't. It is useful, and documented in Writing R Extensions. We only have a small number of hooks. This is a potent one.