Support C++26 via plugin (closes #1380) (#1381)

* Support C++26

Tested locally and had success with R-devel but not R-release but that may
well be due to my R-release being the packaged .deb built with a more
conservative g++ version.  A local R 4.5.0 should also work with proper g++
or clang++

* Roll minor version and date

Author: eddelbuettel

ChangeLog

@@ -1,3 +1,10 @@
+2025-05-06  Dirk Eddelbuettel  <[email protected]>
+
+	* DESCRIPTION (Version, Date): Roll micro version and date
+	* inst/include/Rcpp/config.h: Idem
+
+	* R/Attributes.R: Support C++26 via plugin
+
 2025-05-05  Dirk Eddelbuettel  <[email protected]>
 
 	* inst/tinytest/test_sugar.R: Condition four NA-related tests away on

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: Rcpp
 Title: Seamless R and C++ Integration
-Version: 1.0.14.12
-Date: 2025-03-31
+Version: 1.0.14.13
+Date: 2025-05-06
 Authors@R: c(person("Dirk", "Eddelbuettel", role = c("aut", "cre"), email = "[email protected]",
                     comment = c(ORCID = "0000-0001-6419-907X")),
              person("Romain", "Francois", role = "aut",

R/Attributes.R

@@ -560,6 +560,13 @@ compileAttributes <- function(pkgdir = ".", verbose = getOption("verbose")) {
         list(env = list(PKG_CXXFLAGS ="-std=c++23"))
 }
 
+# built-in C++26 plugin for C++26
+.plugins[["cpp26"]] <- function() {
+    if (getRversion() >= "4.5")         # with recent R versions, R can decide
+        list(env = list(USE_CXX26 = "yes"))
+    else
+        list(env = list(PKG_CXXFLAGS ="-std=c++26"))
+}
 
 ## built-in C++1z plugin for C++17 standard under development
 ## note that as of Feb 2017 this is taken to be a moving target

inst/include/Rcpp/config.h

@@ -30,7 +30,7 @@
 #define RCPP_VERSION_STRING     "1.0.14"
 
 // the current source snapshot (using four components, if a fifth is used in DESCRIPTION we ignore it)
-#define RCPP_DEV_VERSION        RcppDevVersion(1,0,14,12)
-#define RCPP_DEV_VERSION_STRING "1.0.14.12"
+#define RCPP_DEV_VERSION        RcppDevVersion(1,0,14,13)
+#define RCPP_DEV_VERSION_STRING "1.0.14.13"
 
 #endif