add test for downstream use of the scalable allocator

generates a small package using scalable_malloc and scalable_free via
the RcppParallel::CxxFlags() / RcppParallelLibs() flags, installs it,
and confirms the allocator can be used. on windows, this exercises the
tbbmalloc re-export from RcppParallel.dll; elsewhere, the run-time
resolution of tbbmalloc symbols loaded by RcppParallel::.onLoad().

the test builds a package, so it runs only on CI (or with NOT_CRAN),
and only when the tbb backend is enabled.

Author: kevinushey

tests/scalable-allocator.R

@@ -0,0 +1,106 @@
+
+# Check that packages using TBB's scalable allocator can be compiled, linked,
+# and loaded against this installation of RcppParallel.
+#
+# On Windows, downstream packages link only '-lRcppParallel', and so this
+# requires RcppParallel.dll to re-export the tbbmalloc API on their behalf.
+# On other platforms, the symbols are left undefined at link time, and
+# resolved from the tbbmalloc library loaded when RcppParallel is loaded.
+#
+# https://github.com/RcppCore/RcppParallel/pull/262
+
+library(RcppParallel)
+
+# building the test package requires a toolchain, so keep this test
+# off of CRAN's machines
+ci <- nzchar(Sys.getenv("CI")) || identical(Sys.getenv("NOT_CRAN"), "true")
+if (!ci) {
+   writeLines("Not running on CI; skipping scalable allocator test.")
+   quit(save = "no")
+}
+
+# the scalable allocator is only available with the TBB backend
+if (!RcppParallel:::TBB_ENABLED) {
+   writeLines("TBB is not enabled; skipping scalable allocator test.")
+   quit(save = "no")
+}
+
+# generate the test package
+pkgRoot <- file.path(tempdir(), "scalabletest")
+dir.create(file.path(pkgRoot, "src"), recursive = TRUE, showWarnings = FALSE)
+
+writeLines(con = file.path(pkgRoot, "DESCRIPTION"), c(
+   "Package: scalabletest",
+   "Type: Package",
+   "Title: Test Linking to the TBB Scalable Allocator",
+   "Version: 0.1.0",
+   "Author: RcppParallel Authors",
+   "Maintainer: RcppParallel Authors <noreply@example.com>",
+   "Description: Confirms that packages can use the TBB scalable allocator.",
+   "License: GPL-2",
+   "Imports: RcppParallel"
+))
+
+writeLines(con = file.path(pkgRoot, "NAMESPACE"), c(
+   "useDynLib(scalabletest)",
+   "importFrom(RcppParallel, RcppParallelLibs)"
+))
+
+writeLines(con = file.path(pkgRoot, "src", "Makevars"), c(
+   'PKG_CXXFLAGS = $(shell "${R_HOME}/bin/Rscript" -e "RcppParallel::CxxFlags()")',
+   'PKG_LIBS = $(shell "${R_HOME}/bin/Rscript" -e "RcppParallel::RcppParallelLibs()")'
+))
+
+writeLines(con = file.path(pkgRoot, "src", "Makevars.win"), c(
+   'PKG_CXXFLAGS = $(shell "${R_HOME}/bin${R_ARCH_BIN}/Rscript.exe" -e "RcppParallel::CxxFlags()")',
+   'PKG_LIBS = $(shell "${R_HOME}/bin${R_ARCH_BIN}/Rscript.exe" -e "RcppParallel::RcppParallelLibs()")'
+))
+
+writeLines(con = file.path(pkgRoot, "src", "scalable.cpp"), c(
+   "#include <tbb/scalable_allocator.h>",
+   "",
+   "#include <R.h>",
+   "#include <Rinternals.h>",
+   "",
+   'extern "C" SEXP scalable_roundtrip(SEXP sizeSEXP)',
+   "{",
+   "   int size = Rf_asInteger(sizeSEXP);",
+   "",
+   "   double* data = (double*) scalable_malloc(size * sizeof(double));",
+   "   if (data == NULL)",
+   "      return Rf_ScalarLogical(FALSE);",
+   "",
+   "   for (int i = 0; i < size; i++)",
+   "      data[i] = i;",
+   "",
+   "   double total = 0.0;",
+   "   for (int i = 0; i < size; i++)",
+   "      total += data[i];",
+   "",
+   "   scalable_free(data);",
+   "",
+   "   double expected = (double) size * (size - 1) / 2;",
+   "   return Rf_ScalarLogical(total == expected);",
+   "}"
+))
+
+# install it, making sure child processes resolve this RcppParallel
+libDir <- file.path(tempdir(), "library")
+dir.create(libDir, recursive = TRUE, showWarnings = FALSE)
+Sys.setenv(R_LIBS = paste(.libPaths(), collapse = .Platform$path.sep))
+
+rExe <- file.path(R.home("bin"), if (.Platform$OS.type == "windows") "R.exe" else "R")
+args <- c("CMD", "INSTALL", "--no-multiarch", paste0("--library=", shQuote(libDir)), shQuote(pkgRoot))
+
+output <- suppressWarnings(system2(rExe, args, stdout = TRUE, stderr = TRUE))
+writeLines(output)
+
+status <- attr(output, "status")
+if (is.numeric(status) && status != 0L)
+   stop("error installing test package (status code ", status, ")")
+
+# load it, and check that the scalable allocator can be used
+invisible(loadNamespace("scalabletest", lib.loc = libDir))
+ok <- .Call("scalable_roundtrip", 1000L, PACKAGE = "scalabletest")
+writeLines(paste("scalable allocator round trip:", if (isTRUE(ok)) "OK" else "FAILED"))
+stopifnot(isTRUE(ok))