On Wed, 6 Oct 2021 16:44:25 GMT, Yumin Qi <mi...@openjdk.org> wrote: >> src/hotspot/share/cds/filemap.cpp line 1205: >> >>> 1203: } >>> 1204: >>> 1205: _header = (FileMapHeader*)os::malloc(gen_header->_header_size, >>> mtInternal); >> >> There's no need to allocate and read the header again. It's already in >> gen_header. This should be enough: >> >> >> _header = (FileMapHeader*)gen_header; > > see above reply. We need read the full _header_size for _header. Also note > that helper class will delete gen_header when out of scope.
I see. I think your current code is fine. Note that the current code writes the header as a FileMapHeader, but it reads it as both a FileMapHeader and a CDSFileMapHeaderBase. So it has the basic assumption `FileMapHeader::_generic_header` is at offset 0 of FileMapHeader. Therefore, in FileHeaderHelper::initialize, we should add an assert: static_assert(offsetof(FileMapHeader, _generic_header) == 0, "must be"); ------------- PR: https://git.openjdk.java.net/jdk/pull/5768
