src/share/vm/runtime/arguments.cpp

rev 6853 : 8046070: Class Data Sharing clean up and refactoring
Summary: Cleaned up CDS to be more configurable, maintainable and extensible
Reviewed-by: dholmes, coleenp, acorn, mchung

@@ -21,10 +21,11 @@
  * questions.
  *
  */
 
 #include "precompiled.hpp"
+#include "classfile/classLoader.hpp"
 #include "classfile/javaAssertions.hpp"
 #include "classfile/stringTable.hpp"
 #include "classfile/symbolTable.hpp"
 #include "compiler/compilerOracle.hpp"
 #include "memory/allocation.inline.hpp"

@@ -41,10 +42,11 @@
 #include "runtime/vm_version.hpp"
 #include "services/management.hpp"
 #include "services/memTracker.hpp"
 #include "utilities/defaultStream.hpp"
 #include "utilities/macros.hpp"
+#include "utilities/stringUtils.hpp"
 #include "utilities/taskqueue.hpp"
 #if INCLUDE_ALL_GCS
 #include "gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp"
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"

@@ -1113,15 +1115,15 @@
 
 #if defined(COMPILER2) || defined(_LP64) || !INCLUDE_CDS
 // Conflict: required to use shared spaces (-Xshare:on), but
 // incompatible command line options were chosen.
 
-static void no_shared_spaces() {
+static void no_shared_spaces(const char* message) {
   if (RequireSharedSpaces) {
     jio_fprintf(defaultStream::error_stream(),
       "Class data sharing is inconsistent with other specified options.\n");
-    vm_exit_during_initialization("Unable to use shared archive.", NULL);
+    vm_exit_during_initialization("Unable to use shared archive.", message);
   } else {
     FLAG_SET_DEFAULT(UseSharedSpaces, false);
   }
 }
 #endif

@@ -1579,11 +1581,11 @@
   // server performance.  When -server is specified, keep the default off
   // unless it is asked for.  Future work: either add bytecode rewriting
   // at link time, or rewrite bytecodes in non-shared methods.
   if (!DumpSharedSpaces && !RequireSharedSpaces &&
       (FLAG_IS_DEFAULT(UseSharedSpaces) || !UseSharedSpaces)) {
-    no_shared_spaces();
+    no_shared_spaces("COMPILER2 default: -Xshare:auto | off, have to manually setup to on.");
   }
 #endif
 
   set_conservative_max_heap_alignment();
 

@@ -3300,21 +3302,76 @@
     } else if (is_bad_option(option, args->ignoreUnrecognized)) {
       return JNI_ERR;
     }
   }
 
+  // PrintSharedArchiveAndExit will turn on
+  //   -Xshare:on
+  //   -XX:+TraceClassPaths
+  if (PrintSharedArchiveAndExit) {
+    FLAG_SET_CMDLINE(bool, UseSharedSpaces, true);
+    FLAG_SET_CMDLINE(bool, RequireSharedSpaces, true);
+    FLAG_SET_CMDLINE(bool, TraceClassPaths, true);
+  }
+
   // Change the default value for flags  which have different default values
   // when working with older JDKs.
 #ifdef LINUX
  if (JDK_Version::current().compare_major(6) <= 0 &&
       FLAG_IS_DEFAULT(UseLinuxPosixThreadCPUClocks)) {
     FLAG_SET_DEFAULT(UseLinuxPosixThreadCPUClocks, false);
   }
 #endif // LINUX
+  fix_appclasspath();
   return JNI_OK;
 }
 
+// Remove all empty paths from the app classpath (if IgnoreEmptyClassPaths is enabled)
+//
+// This is necessary because some apps like to specify classpath like -cp foo.jar:${XYZ}:bar.jar
+// in their start-up scripts. If XYZ is empty, the classpath will look like "-cp foo.jar::bar.jar".
+// Java treats such empty paths as if the user specified "-cp foo.jar:.:bar.jar". I.e., an empty
+// path is treated as the current directory.
+//
+// This causes problems with CDS, which requires that all directories specified in the classpath
+// must be empty. In most cases, applications do NOT want to load classes from the current
+// directory anyway. Adding -XX:+IgnoreEmptyClassPaths will make these applications' start-up
+// scripts compatible with CDS.
+void Arguments::fix_appclasspath() {
+  if (IgnoreEmptyClassPaths) {
+    const char separator = *os::path_separator();
+    const char* src = _java_class_path->value();
+
+    // skip over all the leading empty paths
+    while (*src == separator) {
+      src ++;
+    }
+
+    char* copy = AllocateHeap(strlen(src) + 1, mtInternal);
+    strncpy(copy, src, strlen(src) + 1);
+
+    // trim all trailing empty paths
+    for (char* tail = copy + strlen(copy) - 1; tail >= copy && *tail == separator; tail--) {
+      *tail = '\0';
+    }
+
+    char from[3] = {separator, separator, '\0'};
+    char to  [2] = {separator, '\0'};
+    while (StringUtils::replace_no_expand(copy, from, to) > 0) {
+      // Keep replacing "::" -> ":" until we have no more "::" (non-windows)
+      // Keep replacing ";;" -> ";" until we have no more ";;" (windows)
+    }
+
+    _java_class_path->set_value(copy);
+    FreeHeap(copy); // a copy was made by set_value, so don't need this anymore
+  }
+
+  if (!PrintSharedArchiveAndExit) {
+    ClassLoader::trace_class_path("[classpath: ", _java_class_path->value());
+  }
+}
+
 jint Arguments::finalize_vm_init_args(SysClassPath* scp_p, bool scp_assembly_required) {
   // This must be done after all -D arguments have been processed.
   scp_p->expand_endorsed();
 
   if (scp_assembly_required || scp_p->get_endorsed() != NULL) {

@@ -3481,13 +3538,12 @@
     if (!UseCompressedOops || !UseCompressedClassPointers) {
       vm_exit_during_initialization(
         "Cannot dump shared archive when UseCompressedOops or UseCompressedClassPointers is off.", NULL);
     }
   } else {
-    // UseCompressedOops and UseCompressedClassPointers must be on for UseSharedSpaces.
     if (!UseCompressedOops || !UseCompressedClassPointers) {
-      no_shared_spaces();
+      no_shared_spaces("UseCompressedOops and UseCompressedClassPointers must be on for UseSharedSpaces.");
     }
 #endif
   }
 }
 

@@ -3723,11 +3779,11 @@
   if ((UseSharedSpaces && FLAG_IS_CMDLINE(UseSharedSpaces)) || PrintSharedSpaces) {
     warning("Shared spaces are not supported in this VM");
     FLAG_SET_DEFAULT(UseSharedSpaces, false);
     FLAG_SET_DEFAULT(PrintSharedSpaces, false);
   }
-  no_shared_spaces();
+  no_shared_spaces("CDS Disabled");
 #endif // INCLUDE_CDS
 
   return JNI_OK;
 }