Don't use new eval API unless RCPP_PROTECTED_EVAL is defined

Author: lionel-

ChangeLog

@@ -16,9 +16,10 @@
         catch those, consider using Rcpp_fast_eval() instead to avoid the
         overhead.
 
-        These improvements are only available for R 3.5.0 and greater. When
-        compiled with old versions of R, Rcpp_fast_eval() falls back to
-        Rcpp_eval(). This is in contrast to internal::Rcpp_eval_impl() which
+        These improvements are only available for R 3.5.0 and greater. You also
+        need to explicitly define `RCPP_PROTECTED_EVAL` before including Rcpp.h.
+        When compiled with old versions of R, Rcpp_fast_eval() always falls back
+        to Rcpp_eval(). This is in contrast to internal::Rcpp_eval_impl() which
         falls back to Rf_eval() and which is used in performance-sensititive
         places.
 

inst/NEWS.Rd

@@ -11,20 +11,21 @@
       set an initial format string (Dirk in \ghpr{777} fixing \ghit{776}).
       \item The 'new' Date and Datetime vectors now have \code{is_na} methods
       too. (Dirk in \ghpr{783} fixing \ghit{781}).
-
       \item Evaluation of R code is now safer when compiled against R
-      3.5. Longjumps of all kinds (condition catching, returns,
-      restarts, debugger exit) are appropriately detected and handled,
-      e.g. the C++ stack unwinds correctly. The new function
-      \code{Rcpp_fast_eval()} can be used for performance-sensitive
-      evaluation of R code. Unlike \code{Rcpp_eval()}, it does not try
-      to catch errors with \code{tryEval} in order to avoid the catching
-      overhead. While this is safe thanks to the stack unwinding
-      protection, this also means that R errors are not transformed to
-      an \code{Rcpp::exception}. If you are relying on error rethrowing,
-      you have to use the slower \code{Rcpp_eval()}. On old R versions
-      \code{Rcpp_fast_eval()} falls back to \code{Rcpp_eval()} so it is
-      safe to use against any versions of R.
+      3.5 (you also need to explicitly define \code{RCPP_PROTECTED_EVAL}
+      before including \code{Rcpp.h}). Longjumps of all kinds (condition
+      catching, returns, restarts, debugger exit) are appropriately
+      detected and handled, e.g. the C++ stack unwinds correctly.
+      \item The new function \code{Rcpp_fast_eval()} can be used for
+      performance-sensitive evaluation of R code. Unlike
+      \code{Rcpp_eval()}, it does not try to catch errors with
+      \code{tryEval} in order to avoid the catching overhead. While this
+      is safe thanks to the stack unwinding protection, this also means
+      that R errors are not transformed to an \code{Rcpp::exception}. If
+      you are relying on error rethrowing, you have to use the slower
+      \code{Rcpp_eval()}. On old R versions \code{Rcpp_fast_eval()}
+      falls back to \code{Rcpp_eval()} so it is safe to use against any
+      versions of R.
     }
     \item Changes in Rcpp Attributes:
     \itemize{

inst/include/Rcpp/api/meat/Rcpp_eval.h

@@ -21,15 +21,15 @@
 #include <Rcpp/Interrupt.h>
 #include <Rversion.h>
 
-#if (defined(R_VERSION) && R_VERSION >= R_Version(3, 5, 0))
-#define R_HAS_UNWIND
+#if (defined(RCPP_PROTECTED_EVAL) && defined(R_VERSION) && R_VERSION >= R_Version(3, 5, 0))
+#define RCPP_USE_PROTECT_UNWIND
 #endif
 
 
 namespace Rcpp {
 namespace internal {
 
-#ifdef R_HAS_UNWIND
+#ifdef RCPP_USE_PROTECT_UNWIND
 
     struct EvalData {
         SEXP expr;
@@ -65,7 +65,7 @@ namespace internal {
 } // namespace internal
 
 
-#ifdef R_HAS_UNWIND
+#ifdef RCPP_USE_PROTECT_UNWIND
 
     inline SEXP Rcpp_fast_eval(SEXP expr, SEXP env) {
         internal::EvalData data(expr, env);

inst/include/Rcpp/exceptions.h

@@ -119,7 +119,7 @@ namespace Rcpp {
         };
 
         inline void resumeJump(SEXP token) {
-#if (defined(R_VERSION) && R_VERSION >= R_Version(3, 5, 0))
+#if (defined(RCPP_PROTECTED_EVAL) && defined(R_VERSION) && R_VERSION >= R_Version(3, 5, 0))
             ::R_ContinueUnwind(token);
 #endif
         }

inst/unitTests/cpp/misc.cpp

@@ -19,6 +19,8 @@
 // You should have received a copy of the GNU General Public License
 // along with Rcpp.  If not, see <http://www.gnu.org/licenses/>.
 
+#define RCPP_PROTECTED_EVAL
+
 #include <Rcpp.h>
 using namespace Rcpp;
 using namespace std;