gcc/libstdc++-v3 ChangeLog include/bits/basic_ ...

[paolo@gcc.gnu.org]

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	paolo@gcc.gnu.org	2003-06-13 20:59:42

Modified files:
	libstdc++-v3   : ChangeLog 
	libstdc++-v3/include/bits: basic_string.h basic_string.tcc 

Log message:
	2003-06-13  Nathan C. Myers <ncm-nospam@cantrip.org>
	
	Avoid multi-processor bus contention on increment/decrement-and-
	test of the reference count in the empty-string object, by comparing
	addresses first, and never touching the reference count of the empty-
	string object.
	* include/bits/basic_string.h:
	(_S_empty_rep_storage): Move into basic_string<>::_Rep for use by its
	members.
	(_Rep::_S_empty_rep()): New accessor.
	(_Rep::_M_length, _Rep::_M_capacity, _Rep::_M_references): Move to
	a base class _Rep_base.
	(_Rep::_M_dispose, _Rep::_M_refcopy): Check for the empty string.
	(basic_string()): Change to use _M_refdata() in place of _M_refcopy(),
	since no longer must increment its refcount.
	* include/bits/basic_string.tcc:
	(_Rep::_M_destroy, _M_leak_hard): Check for the empty string and
	return immediately.  The former might be unnecessary.  The latter
	prevents begin() and end() from cloning it unnecessarily.
	(_S_construct(_InIterator, _InIterator, const _Alloc&,
	input_iterator_tag), _S_construct(_InIterator, _InIterator,
	const _Alloc&, forward_iterator_tag), _S_construct(size_type, _CharT,
	const _Alloc&)): Change to use _M_refdata() in place of _M_refcopy().
	(_M_mutate): Check for the empty string and treat it as shared.
	This is necessary here because _M_mutate is sometimes called with
	all-zero arguments; in all other uses of _M_is_shared, the test comes
	out right anyhow.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/libstdc++-v3/ChangeLog.diff?cvsroot=gcc&r1=1.1768&r2=1.1769
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/libstdc++-v3/include/bits/basic_string.h.diff?cvsroot=gcc&r1=1.33&r2=1.34
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/libstdc++-v3/include/bits/basic_string.tcc.diff?cvsroot=gcc&r1=1.37&r2=1.38