Further macOS OpenMP tweaks (#497)

* Plugin uses "$(SHLIB_OPENMP_CFLAGS)" on macOS too, simplifies opnemp

* Silence whining on windows and limit it to legacy

* Generalize OpenMP setup under macos as suggested by @coatless

* Refinements from code review

* Reword one DEFINE as discussed

Author: eddelbuettel

ChangeLog

@@ -1,3 +1,14 @@
+2025-11-13  Dirk Eddelbuettel  <edd@debian.org>
+
+	* R/inline.R (inlineCxxPlugin): No longer special-case macOS for
+	OpenMP but rely on "$(SHLIB_OPENMP_CFLAGS)" as everywhere else
+
+	* inst/include/RcppArmadillo/config/RcppArmadilloConfigGenerated.h.in:
+	Refine macOS OpenMP detection, respect RCPPARMADILLO_MACOS_DISABLE_OPENMP
+
+	* inst/include/RcppArmadillo/config/RcppArmadilloConfig.h:
+	ARMA_CRIPPLED_LAPACK is only defined if 'LEGACY' Armadillo selected
+
 2025-11-04  Dirk Eddelbuettel  <edd@debian.org>
 
 	* README.md: Minor edits

R/inline.R

@@ -1,4 +1,4 @@
-## Copyright (C) 2010 - 2024  Dirk Eddelbuettel, Romain Francois and Douglas Bates
+## Copyright (C) 2010 - 2025  Dirk Eddelbuettel, Romain Francois and Douglas Bates
 ##
 ## This file is part of RcppArmadillo.
 ##
@@ -16,8 +16,7 @@
 ## along with RcppArmadillo.  If not, see <http://www.gnu.org/licenses/>.
 
 inlineCxxPlugin <- function(...) {
-    ismacos <- Sys.info()[["sysname"]] == "Darwin"
-    openmpflag <- if (ismacos) "" else "$(SHLIB_OPENMP_CFLAGS)"
+    openmpflag <- "$(SHLIB_OPENMP_CFLAGS)"
     plugin <-  Rcpp::Rcpp.plugin.maker(include.before = "#include <RcppArmadillo.h>",
                                        libs           = paste(openmpflag, "$(LAPACK_LIBS) $(BLAS_LIBS) $(FLIBS)"),
                                        package        = "RcppArmadillo")

inst/include/RcppArmadillo/config/RcppArmadilloConfig.h

@@ -1,9 +1,9 @@
 
 // RcppArmadilloConfig.h: Rcpp/Armadillo glue
 //
-// Copyright (C)  2010 - 2022  Dirk Eddelbuettel, Romain Francois and Douglas Bates
-// Copyright (C)  2016 - 2022  George G. Vega Yon
-// Copyright (C)  2017 - 2022  Serguei Sokol
+// Copyright (C)  2010 - 2025  Dirk Eddelbuettel, Romain Francois and Douglas Bates
+// Copyright (C)  2016 - 2025  George G. Vega Yon
+// Copyright (C)  2017 - 2025  Serguei Sokol
 //
 // This file is part of RcppArmadillo.
 //
@@ -99,7 +99,12 @@
   // R can be built with its own Rlapack library, or use an external
   // one. Only the latter has zgesdd, a complex-valued SVD using divide-and-conquer
   // on Windows we do not assume ZGESDD
-  #define ARMA_CRIPPLED_LAPACK 1
+  //
+  // Update 2025-Nov: R now generally has good enough LAPACK/BLAS, and newer Arma
+  // versions whine so protecting this now for use with Armadillo older than 15.*
+  #if defined(ARMA_SELECTED_LEGACY_VERSION)
+    #define ARMA_CRIPPLED_LAPACK 1
+  #endif
   // on Windows we can now assume OpenMP with Rtools / gcc 4.9.3
   // note that performance is said to still be poor
   // cf https://cran.r-project.org/doc/manuals/r-devel/R-admin.html#The-MinGW_002dw64-toolchain

inst/include/RcppArmadillo/config/RcppArmadilloConfigGenerated.h.in

@@ -1,7 +1,8 @@
 
-// RcppArmadilloGenerated.h: Autoconf-updated file for LAPACK and OpenMP choices
+// RcppArmadilloConfigGenerated.h: Autoconf-updated file for LAPACK and OpenMP choices
 //
-// Copyright (C)  2013 - 2021  Dirk Eddelbuettel
+// Copyright (C)  2013 - 2025  Dirk Eddelbuettel
+//                       2025  James J. Balamuta
 //
 // This file is part of RcppArmadillo.
 //
@@ -21,9 +22,19 @@
 #ifndef RcppArmadillo__RcppArmadilloConfigGenerated__h
 #define RcppArmadillo__RcppArmadilloConfigGenerated__h
 
-#ifndef ARMA_USE_OPENMP
-// from configure test for OpenMP based on how R is configured, and whether g++ new enough
-@ARMA_HAVE_OPENMP@
+// macOS special case as discussed in https://github.com/RcppCore/RcppArmadillo/issues/493
+#if !defined(ARMA_USE_OPENMP)
+  #if defined(__APPLE__) && defined(_OPENMP)
+    // User has OpenMP available, but check if they want it disabled
+    #ifndef RCPPARMADILLO_MACOS_DISABLE_OPENMP
+      #define ARMA_USE_OPENMP 1
+    #else
+      #define ARMA_DONT_USE_OPENMP 1
+    #endif
+  #else
+    // from configure test for OpenMP based on how R is configured
+    @ARMA_HAVE_OPENMP@
+  #endif
 #endif
 
 #endif