make sure RcppParallel still builds with older R

NEWS.md

@@ -2,6 +2,11 @@
 ## RcppParallel 5.1.10  (UNRELEASED)
 
 * RcppParallel now bundles oneTBB 2022.0.0.
+
+* On Windows, RcppParallel now uses the copy of TBB provided by Rtools, if any.
+  If TBB is not available, RcppParallel will use only the fallback 'tinythread'
+  implementation. In practice, this implies that RcppParallel will now only
+  provide a TBB backend with R (>= 4.2.0).
 
 ## RcppParallel 5.1.9
 

R/aaa.R

@@ -1,5 +1,6 @@
 
 # stubs that get overridden via configure script
+TBB_ENABLED <- TRUE
 TBB_LIB  <- ""
 TBB_INC  <- ""
 TBB_NAME <- "tbb"

R/tbb-autodetected.R.in

@@ -1,4 +1,5 @@
 
+TBB_ENABLED <- @TBB_ENABLED@
 TBB_LIB  <- "@TBB_LIB@"
 TBB_INC  <- "@TBB_INC@"
 TBB_NAME <- "@TBB_NAME@"

R/tbb.R

@@ -50,7 +50,8 @@ tbbCxxFlags <- function() {
 
    # opt-in to TBB on Windows
    if (is_windows()) {
-      flags <- c(flags, "-DRCPP_PARALLEL_USE_TBB=1")
+      enabled <- if (TBB_ENABLED) "1" else "0"
+      flags <- c(flags, sprintf("-DRCPP_PARALLEL_USE_TBB=%s", enabled))
       if (R.version$arch == "aarch64") {
          # TBB does not have assembly code for Windows ARM64
          # so we need to use compiler builtins

src/Makevars.in

@@ -7,7 +7,7 @@ TBB_INC   = @TBB_INC@
 TBB_NAME  = @TBB_NAME@
 
 PKG_CPPFLAGS = @PKG_CPPFLAGS@
-PKG_CXXFLAGS = @CXX11STD@ -DRCPP_PARALLEL_USE_TBB=1
+PKG_CXXFLAGS = @PKG_CXXFLAGS@
 
 PKG_LIBS = @PKG_LIBS@ @PKG_LIBS_EXTRA@
 

src/install.libs.R

@@ -89,21 +89,56 @@ useBundledTbb <- function() {
    useTbbPreamble("tbb/include")
    dir.create("tbb/build-tbb", showWarnings = FALSE)
 
+   cmake <- Sys.getenv("CMAKE", unset = "cmake")
+   buildType <- Sys.getenv("CMAKE_BUILD_TYPE", unset = "Release")
+   verbose <- Sys.getenv("VERBOSE", unset = "0")
+
+   cmakeFlags <- c(
+      sprintf("-DCMAKE_BUILD_TYPE=%s", buildType),
+      "-DTBB_TEST=0",
+      "-DTBB_EXAMPLES=0",
+      "-DTBB_STRICT=0",
+      ".."
+   )   
+
    writeLines("*** configuring tbb")
-   status <- system("cd tbb/build-tbb; cmake -DTBB_TEST=0 -DTBB_EXAMPLES=0 -DTBB_STRICT=0 .. > build.log 2>&1")
-   if (status != 0L) {
-      system("cat build.log")
+   owd <- setwd("tbb/build-tbb")
+   output <- system2(cmake, shQuote(cmakeFlags), stdout = TRUE, stderr = TRUE)
+   status <- attr(output, "status")
+   if (is.numeric(status) && status != 0L) {
+      writeLines(output)
       stop("error configuring tbb (status code ", status, ")")
+   } else if (!identical(verbose, "0")) {
+      writeLines(output)
    }
+   setwd(owd)
 
    writeLines("*** building tbb")
-   status <- system("cd tbb/build-tbb; cmake --build . > build.log 2>&1")
-   if (status != 0L) {
-      system("cat build.log")
+   owd <- setwd("tbb/build-tbb")
+   output <- system2(cmake, c("--build", ".", "--config", "release"), stdout = TRUE, stderr = TRUE)
+   status <- attr(output, "status")
+   if (is.numeric(status) && status != 0L) {
+      writeLines(output)
       stop("error building tbb (status code ", status, ")")
+   } else if (!identical(verbose, "0")) {
+      writeLines(output)
    }
+   setwd(owd)
+
+   shlibPattern <- switch(
+      Sys.info()[["sysname"]],
+      Windows = "^tbb.*\\.dll$",
+      Darwin  = "^libtbb.*\\.dylib$",
+      "^libtbb.*\\.so.*$"
+   )
+
+   tbbFiles <- list.files(
+      "tbb/build-tbb",
+      pattern = shlibPattern,
+      recursive = TRUE,
+      full.names = TRUE
+   )
 
-   tbbFiles <- list.files(pattern = "^libtbb\\.(so|dylib)", recursive = TRUE)
    tbbDir <- dirname(tbbFiles[[1L]])
 
    dir.create("tbb/build", showWarnings = FALSE)
@@ -123,6 +158,8 @@ args <- commandArgs(trailingOnly = TRUE)
 if (identical(args, "build")) {
    if (nzchar(tbbLib) && nzchar(tbbInc)) {
       useSystemTbb(tbbLib, tbbInc)
+   } else if (.Platform$OS.type == "windows") {
+      writeLines("** building RcppParallel without tbb backend")
    } else {
       useBundledTbb()
    }

tools/config/configure.R

@@ -107,27 +107,26 @@ switch(
 # on Windows, check for Rtools; if it exists, and we have tbb, use it
 if (.Platform$OS.type == "windows") {
 
+   tbbPattern <- "lib(tbb[^[:alpha:]]*)\\.a$"
    gccPath <- normalizePath(Sys.which("gcc"), winslash = "/")
 
    tbbLib <- Sys.getenv("TBB_LIB", unset = NA)
-   if (is.na(tbbLib)) {
+   if (is.na(tbbLib))
       tbbLib <- normalizePath(file.path(gccPath, "../../lib"), winslash = "/")
-      Sys.setenv(TBB_LIB = tbbLib)
-   }
 
    tbbInc <- Sys.getenv("TBB_INC", unset = NA)
-   if (is.na(tbbInc)) {
+   if (is.na(tbbInc))
       tbbInc <- normalizePath(file.path(gccPath, "../../include"), winslash = "/")
-      Sys.setenv(TBB_INC = tbbInc)
-   }
 
-   tbbPattern <- "lib(tbb[^[:alpha:]]*)\\.a$"
    tbbLibs <- list.files(tbbLib, pattern = tbbPattern)
    if (length(tbbLibs)) {
       tbbName <- gsub(tbbPattern, "\\1", tbbLibs[[1L]])
-      Sys.setenv(TBB_NAME = tbbName)
+      Sys.setenv(
+         TBB_LIB = tbbLib,
+         TBB_INC = tbbInc,
+         TBB_NAME = tbbName
+      )
    }
-
 }
 
 # try and figure out path to TBB
@@ -220,6 +219,11 @@ pkgLibs <- if (!is.na(tbbLib)) {
       "-l$(TBB_NAME)",
       "-ltbbmalloc"
    )
+
+} else if (.Platform$OS.type == "windows") {
+
+   NULL
+
 } else {
 
    c(
@@ -283,6 +287,14 @@ if (!is.na(tbbLib)) {
    define(PKG_CPPFLAGS = "-I../inst/include")
 }
 
+# PKG_CXXFLAGS
+if (.Platform$OS.type == "windows" && is.na(tbbLib)) {
+   define(TBB_ENABLED = FALSE)
+   define(PKG_CXXFLAGS = "-DRCPP_PARALLEL_USE_TBB=0")
+} else {
+   define(TBB_ENABLED = TRUE)
+   define(PKG_CXXFLAGS = "-DRCPP_PARALLEL_USE_TBB=1")
+}
 
 # macOS needs some extra flags set
 if (Sys.info()[["sysname"]] == "Darwin") {