Only set CXX14 when needed by older R versions

.github/workflows/R-CMD-check.yaml

@@ -2,7 +2,6 @@
 # Need help debugging build failures? Start at https://github.com/r-lib/actions#where-to-find-help
 on:
   push:
-    branches: [main, master]
   pull_request:
     branches: [main, master]
 
@@ -19,6 +18,9 @@ jobs:
       matrix:
         config:
           - {os: macos-latest,   r: 'release'}
+          - {os: windows-latest, r: '4.0'}
+          - {os: windows-latest, r: '4.1'}
+          - {os: windows-latest, r: '4.2'}
           - {os: windows-latest, r: 'release'}
           - {os: ubuntu-latest,   r: 'devel', http-user-agent: 'release'}
           - {os: ubuntu-latest,   r: 'release'}

DESCRIPTION

@@ -49,3 +49,4 @@ Encoding: UTF-8
 LazyData: true
 Roxygen: list(markdown = TRUE)
 RoxygenNote: 7.2.3
+Biarch: true

configure.win

@@ -0,0 +1,7 @@
+#!/bin/sh
+MAJOR=${R_VERSION:0:3}
+
+# Older R versions default to CXX11
+if [ "$MAJOR" = "4.1" ] || [ "$MAJOR" = "4.0" ]; then
+echo "CXX_STD = CXX14" >> src/Makevars.win
+fi

src/Makevars.win

@@ -1,3 +1,2 @@
-CXX_STD = CXX14
 PKG_CXXFLAGS = $(SHLIB_OPENMP_CXXFLAGS)
 PKG_LIBS = $(SHLIB_OPENMP_CXXFLAGS) $(LAPACK_LIBS) $(BLAS_LIBS) $(FLIBS)