Allocates hidden extra memory after VirtualMemory, and
verified writes are duplicated at a fixed offset.
This CL only adds the helper.
Next steps:
1. Use Reserve when reserving semi-spaces and heap pages.
2. Use Write for storing pointers (+ offset in generated code).
3. Use Accept for GC-related object lifecycle.
4. Call Verify regularly.
5. Fix failures (= places where we forget/ignore write barriers).
Review URL: https://codereview.chromium.org//641243004
git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@41399 260f80e4-7a28-3924-810f-c04153c831b5
Change executable pages to be read/execute but not writable by default.
All pages are made temporarily writable just before a full GC, because both
the mark and sweep phases write to the pages. When allocating in a page and
when patching code, the pages are made temporarily writable.
The order of allocation of Code and Instructions objects is changed so that
a GC will not occur after Instructions is allocated. (A full GC would
render the Instructions unwritable.) A scoped object is used to make memory
protection simpler.
Original CL: https://codereview.chromium.org/106593002/
I added a cc test that is expected to crash.
R=srdjan@google.com
Review URL: https://codereview.chromium.org//136563002
git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@32493 260f80e4-7a28-3924-810f-c04153c831b5
koda@google.com