first crack at checking compiler versions from R

DESCRIPTION

@@ -21,3 +21,4 @@ URL: http://www.rcpp.org, http://dirk.eddelbuettel.com/code/rcpp.html, https://g
 License: GPL (>= 2)
 BugReports: https://github.com/RcppCore/Rcpp/issues
 MailingList: Please send questions and comments regarding Rcpp to rcpp-devel@lists.r-forge.r-project.org
+RoxygenNote: 5.0.1

R/compilerCheck.R

@@ -0,0 +1,36 @@
+##' Helper function to establish minimal compiler versions, currently limited
+##' only to \code{g++} which (particularly for older RHEL/CentOS releases) is
+##' too far behind current C++11 standards required for some packages.
+##'
+##' This function looks up \code{g++} (as well as optional values in the
+##' \code{CXX} and \code{CXX1X} environment variables) in the \code{PATH}.  For
+##' all values found, the output of \code{g++ -v} is analyzed for the version
+##' string, which is then compared to the given minimal version.
+##' @title Check for Minimal (g++) Compiler Version
+##' @param minVersion An object of type \code{package_version}, with a default
+##'  of version 4.6.0
+##' @return A boolean value is returned, indicating if the minimal version is
+##'  being met
+##' @author Dirk Eddelbuettel
+compilerCheck <- function(minVersion=package_version("4.6.0")) {
+
+    binaries <- c("g++", Sys.getenv("CXX", unset=""), Sys.getenv("CXX1X", unset=""))
+    binpaths <- lapply(binaries, function(b) { if (b=="") NULL else Sys.which(b) })
+
+    allgood <- FALSE
+    rl <- lapply(binpaths, function(b) {
+        if (is.null(b)) return(NULL)
+        con <- pipe(paste(b, "-v 2>&1"), "r") # NB: not --version, but -v
+        lines <- readLines(con)
+        close(con)
+        lines <- lines[grepl("^g.. version", lines)]
+        if (length(lines) == 0) return(NULL)
+        ver <- strsplit(lines, " ")[[1]][3]   # format is 'gcc version x.y.z ....'
+        package_version(ver) >= minVersion
+    })
+    all(do.call(c, rl))                 # drops NULLs
+}
+
+## TODO: maybe not limit to gcc/g++
+## TODO: maybe be smarter about combination of path, CXX and CXX1X ?
+## TODO: maybe make env.var optional arguments too