[gold][patch] Cleanup more mmap leakage

[Cary Coutant <ccoutant at google dot com>]

This patch fixes some more mmap leakage that I've found in processing
thin archives, shared libraries, and during garbage collection. As far
as I can tell now, --no-keep-files-mapped now releases all the memory
it should between passes. These fixes reduce gold's maximum memory
usage slightly, but didn't make any significant performance difference
on the tests I ran.

In most cases, gold is careful to explicitly delete File_view objects
as soon as they are no longer needed, but there were unusual code
paths (e.g., when a shared library is added a second time) that were
missing those explicit delete statements. I chose to add destructors
to make sure that all File_view members are deleted when
Read_symbols_data and Read_relocs_data objects are destroyed, and to
make sure that the Read_symbols_data and Read_relocs_data objects are
destroyed before releasing the associated file (so that
File_read::clear_views would unmap the regions). I didn't bother to
remove the places where the File_view objects were explicitly deleted,
since in those places it's still better to delete them as early as
possible.

No regressions on x86_64. OK to checkin?

-cary

        * archive.cc (include_member): Destroy Read_symbols_data object before
        releasing file.
        * object.cc (Read_symbols_data::~Read_symbols_data) New destructor.
        * object.h (Read_symbols_data::Read_symbols_data) New constructor.
        (Read_symbols_data::~Read_symbols_data) New destructor.
        (Section_relocs::Section_relocs) New constructor.
        (Section_relocs::~Section_relocs) New destructor.
        (Read_relocs_data::Read_relocs_data) New constructor.
        (Read_relocs_data::~Read_relocs_data) New destructor.
        * testsuite/binary_unittest.cc (Sized_binary_test): Set sd member
        pointers to NULL after deleting.

Attachment: gold-unmap-patch.txt
Description: Text document