Calls to UNPROTECT() to quiet rchk (#949)

* Calls to UNPROTECT() to quiet rchk

* ++nprot is more idiomatic

Author: romainfrancois

inst/include/Rcpp/macros/macros.h

@@ -29,9 +29,11 @@
 #ifndef BEGIN_RCPP
 #define BEGIN_RCPP                                                                               \
     int rcpp_output_type = 0 ;                                                                   \
+    int nprot = 0;                                                                               \
     (void)rcpp_output_type;                                                                      \
     SEXP rcpp_output_condition = R_NilValue ;                                                    \
     (void)rcpp_output_condition;                                                                 \
+    static SEXP stop_sym = Rf_install("stop");                                                   \
     try {
 #endif
 
@@ -48,26 +50,30 @@
     catch(Rcpp::exception& __ex__) {                                                             \
        rcpp_output_type = 2 ;                                                                    \
        rcpp_output_condition = PROTECT(rcpp_exception_to_r_condition(__ex__)) ;                  \
+       ++nprot;                                                                                  \
     }                                                                                            \
     catch( std::exception& __ex__ ){                                                             \
        rcpp_output_type = 2 ;                                                                    \
        rcpp_output_condition = PROTECT(exception_to_r_condition(__ex__)) ;                       \
+       ++nprot;                                                                                  \
     }                                                                                            \
     catch( ... ){                                                                                \
        rcpp_output_type = 2 ;                                                                    \
        rcpp_output_condition = PROTECT(string_to_try_error("c++ exception (unknown reason)")) ;  \
+       ++nprot;                                                                                  \
     }                                                                                            \
     if( rcpp_output_type == 1 ){                                                                 \
        Rf_onintr() ;                                                                             \
     }                                                                                            \
     if( rcpp_output_type == 2 ){                                                                 \
-       SEXP stop_sym  = Rf_install( "stop" ) ;                                                   \
        SEXP expr = PROTECT( Rf_lang2( stop_sym , rcpp_output_condition ) ) ;                     \
-       Rf_eval( expr, R_GlobalEnv ) ;                                                            \
+       ++nprot;                                                                                  \
+       Rf_eval( expr, R_BaseEnv ) ;                                                              \
     }                                                                                            \
     if (rcpp_output_type == 3) {                                                                 \
         Rcpp::internal::resumeJump(rcpp_output_condition);                                       \
-    }
+    }                                                                                            \
+    UNPROTECT(nprot);
 #endif
 
 #ifndef END_RCPP