Deprecation warnings on g++ 7.1.0 at MacOS 10.12.4

[alexcpsec]

Not a big deal, everything working as intended, but you may want to look at these warnings when building code with Rcpp using g++ 7.1.0

In file included from /Library/Frameworks/R.framework/Versions/3.3/Resources/library/Rcpp/include/Rcpp/Module.h:338:0,
                 from /Library/Frameworks/R.framework/Versions/3.3/Resources/library/Rcpp/include/Rcpp.h:64,
                 from osutil.cpp:1:
/Library/Frameworks/R.framework/Versions/3.3/Resources/library/Rcpp/include/Rcpp/module/Module_Property.h:103:41: warning: dynamic exception specifications are deprecated in C++11 [-Wdeprecated]
     void set(Class* object, SEXP value) throw(std::range_error,Rcpp::not_compatible){
                                         ^~~~~
/Library/Frameworks/R.framework/Versions/3.3/Resources/library/Rcpp/include/Rcpp/module/Module_Property.h:161:41: warning: dynamic exception specifications are deprecated in C++11 [-Wdeprecated]
     void set(Class* object, SEXP value) throw(std::range_error,Rcpp::not_compatible){
                                         ^~~~~

[eddelbuettel]

Appreciate that! Noticed that 7.1 is out and that I can probably get it in Debian unstable too.

Would you know what the new and recommended form is?

[alexcpsec]

Sorry, no clue. C++11 reads like black magic incantations to me. :(

[eddelbuettel]

Some somewhat dense stuff here at cppreference.com.

[kevinushey]

Here's the associated paper:

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3051.html

From what I read, the tl;dr is: don't use exception specifications to dictate what type of exception can / should be thrown; just leave it out. It's only worth specifying when you want to indicate that a function will not throw an exception (as it enables certain optimizations).

The simplest fix is to just delete that throw(...) code.

[eddelbuettel]

Thanks so much -- I can certainly fire up a Debian unstable Docker container and try that.

[epipping]

I've just come across these warnings as well. However, while in C++11 and C++14 mode they're indeed warnings, in C++17 mode they're errors for me, making this quite a bit more pressing (since all you need to do to get these errors is to #include <Rcpp.h>, this renders Rcpp unusable with g++ in C++17 mode for now).

In file included from /usr/local/lib/R/3.4/site-library/Rcpp/include/Rcpp/Module.h:338:0,
                 from /usr/local/lib/R/3.4/site-library/Rcpp/include/Rcpp.h:64,
                 from foo.cc:1:
/usr/local/lib/R/3.4/site-library/Rcpp/include/Rcpp/module/Module_Property.h:103:41: error: ISO C++1z does not allow dynamic exception specifications
     void set(Class* object, SEXP value) throw(std::range_error,Rcpp::not_compatible){
                                         ^~~~~
/usr/local/lib/R/3.4/site-library/Rcpp/include/Rcpp/module/Module_Property.h:161:41: error: ISO C++1z does not allow dynamic exception specifications
     void set(Class* object, SEXP value) throw(std::range_error,Rcpp::not_compatible){
                                         ^~~~~
make: *** [foo.o] Error 1
g++-7 -I/usr/local/Cellar/r/3.4.0_1/R.framework/Resources/include -DNDEBUG   -I"/usr/local/lib/R/3.4/site-library/Rcpp/include" -I"/Users/pipping" -I/usr/local/opt/gettext/include -I/usr/local/opt/readline/include -I/usr/local/include  -std=c++17 -fPIC  -g -O2  -c foo.cc -o foo.o

According to this thread on gcc-dev there is no way to demote this error to a warning.

[eddelbuettel]

We will take care of them.

In the meantime, and as you're at it, could you confirm that commenting out / removing these two suppresses the issue? It should have no effect on code or behaviour.

[epipping]

The change

--- /usr/local/lib/R/3.4/site-library/Rcpp/include/Rcpp/module/Module_Property.h.bak	2017-05-06 14:13:01.000000000 +0200
+++ /usr/local/lib/R/3.4/site-library/Rcpp/include/Rcpp/module/Module_Property.h	2017-05-06 14:14:02.000000000 +0200
@@ -100,7 +100,7 @@
     SEXP get(Class* object) {
         return Rcpp::wrap( (object->*getter)() ) ;
     }
-    void set(Class* object, SEXP value) throw(std::range_error,Rcpp::not_compatible){
+    void set(Class* object, SEXP value) {
         (object->*setter)(
                           Rcpp::as< typename Rcpp::traits::remove_const_and_reference< PROP >::type >( value )
                            ) ;
@@ -158,7 +158,7 @@
     SEXP get(Class* object) {
         return Rcpp::wrap( (object->*getter)() ) ;
     }
-    void set(Class* object, SEXP value) throw(std::range_error,Rcpp::not_compatible){
+    void set(Class* object, SEXP value) {
         setter( object,
                 Rcpp::as< typename Rcpp::traits::remove_const_and_reference< PROP >::type >( value )
                 ) ;

allows me to compile the file in C++17 mode, yes.

Update: It might be worth mentioning that even with -Wall -Wextra, afterwards, I do not get any warnings.