Improve {lib,}jvm.{so,dylib,dll} loading

R/zzz.R.in

@@ -1,9 +1,71 @@
+getMakeconfVar <- function(makeconf, var) {
+  # With some assistance from:
+  # https://github.com/r-hub/sysreqs/blob/master/R/platform.R
+  result <- grep(paste("^", var, "[ ]?=",sep=''), makeconf, value = TRUE)
+  sub(paste("^", var, "[ ]?=[ ]?", sep=''), "", result)
+}
+
 .onLoad <- function(libname, pkgname) {
-  Sys.setenv("LD_LIBRARY_PATH"=paste(Sys.getenv("LD_LIBRARY_PATH"),"@JAVA_LD@",sep=':'))
+  # Conda refuses to mess with LD_LIBRARY_PATH (etc/ldconfig does not do that now)
+  # as it is the Linux equivalent of DLL-hell and has caused real problems with
+  # R, instead we pre-load libjvm.so from the location detected by javareconf.
+  Makeconf <- readLines(file.path(R.home(), "etc", Sys.getenv('R_ARCH'), "Makeconf"))
+  dylib_ext <- getMakeconfVar(Makeconf, "DYLIB_EXT")
+  if (length(grep("^mingw", R.version$os))) {
+    exe_ext <- ".exe"
+    lib_prefix <- ""
+  } else {
+    exe_ext <- ""
+    lib_prefix <- "lib"
+  }
+  jvm_fname = paste(lib_prefix, "jvm", dylib_ext, sep='')
+  jh <- getMakeconfVar(Makeconf, "JAVA_HOME")
+  j_ld_lp <- gsub("$(JAVA_HOME)", jh, getMakeconfVar(Makeconf, "JAVA_LD_LIBRARY_PATH"), fixed=TRUE)
+  jvm <- file.path(j_ld_lp, jvm_fname)
+  if (!length(j_ld_lp) || !file.exists(jvm)) {
+    if (!length(jh)) {
+      # In this case (which will always happen on Windows) fall back to JAVA_HOME
+      jh <- Sys.getenv("JAVA_HOME")
+      java_exe <- file.path(jh, 'bin', paste('java', exe_ext, sep=''))
+      Javaconf <- system2(java_exe, args=c("-XshowSettings:properties", "-version"), stderr = TRUE, stdout = TRUE, minimized = TRUE)
+      j_ld_lp <- grep(' *sun\\.boot\\.library\\.path[ ]?=', Javaconf, perl = TRUE, value = TRUE)
+      j_ld_lp <- sub(' *sun\\.boot\\.library\\.path[ ]?=[ ]?', "", j_ld_lp)
+      if (file.exists(file.path(j_ld_lp, "server", jvm_fname))) {
+        j_ld_lp <- file.path(j_ld_lp, "server")
+      } else if (file.exists(file.path(j_ld_lp, "client", jvm_fname))) {
+        j_ld_lp <- file.path(j_ld_lp, "client")
+      }
+    }
+  }
+  jvm <- file.path(j_ld_lp, jvm_fname)
+
+  if (length(grep("^darwin", R.version$os)))  {
+    # NYI, need to re-create the dylib stub to point to the real JVM dylib
+  } else if (length(grep("^linux", R.version$os))) {
+    if (file.exists(jvm)) {
+      dyn.load(jvm, local=FALSE, now=TRUE)
+    } else {
+      # This is what the code originally did. Kept as a last resort only, but if it is run
+      # then something bad has happened.
+      Sys.setenv("LD_LIBRARY_PATH"=paste(Sys.getenv("LD_LIBRARY_PATH"),"@JAVA_LD@",sep=':'))
+    }
+  } else if (length(grep("^mingw", R.version$os))) {
+    # When all you have is a hammer. If the dir is not on PATH then add it.
+    # It would be nice here to find the first jvm.dll on PATH and if that
+    # entry comes before our directory (or our directory is not on PATH) then
+    # re-arrange the entries so that ours appears before it. Overkill though?
+    win_j_ld_lp <- gsub("/", "\\\\", j_ld_lp)
+    split_path <- strsplit(Sys.getenv("PATH"), ";")
+    if (!win_j_ld_lp %in% unlist(split_path)) {
+      if (file.exists(win_j_ld_lp) && file.info(win_j_ld_lp)$isdir == TRUE) {
+        Sys.setenv("PATH"=paste(win_j_ld_lp, Sys.getenv("PATH"), sep=';'))
+      }
+    }
+  }
+
   ## On OS X with Oracle Java we may need to work around Oracle bug:
   ## https://bugs.openjdk.java.net/browse/JDK-7131356
   if (length(grep("^darwin", R.version$os)) && file.exists("/usr/libexec/java_home")) {
-     jh <- Sys.getenv("JAVA_HOME")
      if (!nzchar(jh)) jh <- system("/usr/libexec/java_home", intern=TRUE)[1L]
      if (file.exists(file.path(jh, "jre/lib"))) jh <- file.path(jh, "jre")
      if (file.exists(jli <- file.path(jh, "lib/jli/libjli.dylib"))) {