src/hotspot/share/cds/archiveUtils.cpp

@@ -203,18 +203,32 @@
    log_debug(cds)("Expanding %s spaces by " SIZE_FORMAT_W(7) " bytes [total " SIZE_FORMAT_W(9)  " bytes ending at %p]",
                   which, commit, _vs->actual_committed_size(), _vs->high());
  }
  
  
- char* DumpRegion::allocate(size_t num_bytes) {
-   char* p = (char*)align_up(_top, (size_t)SharedSpaceObjectAlignment);
-   char* newtop = p + align_up(num_bytes, (size_t)SharedSpaceObjectAlignment);
+ char* DumpRegion::allocate(size_t num_bytes, size_t alignment) {
+   // We align the starting address of each allocation.
+   char* p = (char*)align_up(_top, alignment);
+   char* newtop = p + num_bytes;
+   // Leave _top always SharedSpaceObjectAlignment aligned. But not more -
+   //  if we allocate with large alignments, lets not waste the gaps.
+   // Ideally we would not need to align _top to anything here but CDS has
+   //  a number of implicit alignment assumptions. Leaving this unaligned
+   //  here will trip of at least ReadClosure (assuming word alignment) and
+   //  DumpAllocStats (will get confused about counting bytes on 32-bit
+   //  platforms if we align to anything less than SharedSpaceObjectAlignment
+   //  here).
+   newtop = align_up(newtop, SharedSpaceObjectAlignment);
    expand_top_to(newtop);
-   memset(p, 0, newtop - p);
+   memset(p, 0, newtop - p); // todo: needed? debug_only?
    return p;
  }
  
+ char* DumpRegion::allocate(size_t num_bytes) {
+   return allocate(num_bytes, SharedSpaceObjectAlignment);
+ }
+ 
  void DumpRegion::append_intptr_t(intptr_t n, bool need_to_mark) {
    assert(is_aligned(_top, sizeof(intptr_t)), "bad alignment");
    intptr_t *p = (intptr_t*)_top;
    char* newtop = _top + sizeof(intptr_t);
    expand_top_to(newtop);

@@ -307,11 +321,11 @@
  
  void ReadClosure::do_tag(int tag) {
    int old_tag;
    old_tag = (int)(intptr_t)nextPtr();
    // do_int(&old_tag);
-   assert(tag == old_tag, "old tag doesn't match");
+   assert(tag == old_tag, "tag doesn't match (%d, expected %d)", old_tag, tag);
    FileMapInfo::assert_mark(tag == old_tag);
  }
  
  void ReadClosure::do_oop(oop *p) {
    if (UseCompressedOops) {