unconditionally get/put RNG state

ChangeLog

@@ -1,3 +1,8 @@
+2018-02-26  Kevin Ushey  <kevinushey@gmail.com>
+
+        * src/api.cpp: Always set / put RNG state when calling Rcpp function
+
+
 2018-02-25  Dirk Eddelbuettel  <edd@debian.org>
 
         * vignettes/Rcpp.bib: Updated

inst/NEWS.Rd

@@ -6,6 +6,11 @@
 \section{Changes in Rcpp version 0.12.16 (2018-03-xx)}{
   \itemize{
     \item Changes in Rcpp API:
+    \itemize{
+      \item Rcpp now sets and puts the RNG state upon each entry to an Rcpp
+      function, ensuring that nested invocations of Rcpp functions manage the
+      RNG state as expected
+    }
     \itemize{
       \item The \code{long long} type can now be used on 64-bit Windows (Kevin
       in \ghpr{811})

src/api.cpp

@@ -64,22 +64,17 @@ using namespace Rcpp;
 namespace Rcpp {
 
     namespace internal {
-        namespace {
-            unsigned long RNGScopeCounter = 0;
-        }
 
         // [[Rcpp::register]]
         unsigned long enterRNGScope() {
-            if (RNGScopeCounter == 0) GetRNGstate();
-            RNGScopeCounter++;
-            return RNGScopeCounter;
+            GetRNGstate();
+            return 0;
         }
 
         // [[Rcpp::register]]
         unsigned long exitRNGScope() {
-            RNGScopeCounter--;
-            if (RNGScopeCounter == 0) PutRNGstate();
-            return RNGScopeCounter;
+            PutRNGstate();
+            return 0;
         }
 
         // [[Rcpp::register]]