[PATCH v2] libstdc++: Make certain exceptions transaction_safe.

[Torvald Riegel]

The attached patch makes some exceptions transaction-safe, as require by
the Transactional Memory TS.  I believe I addressed all feedback for the
previous version of this patch (in particular, there are now more safety
checks for preconditions for this implementation (eg, that the new
allocator is used), all exceptions declared by the TM TS are now
supported (with the exception of tx_exception -- should I add that in a
follow-up patch?), and there is a test for the new functionality (as
part of libitm's testsuite)).

There are two things that complicate such support.  First, it seems
better to not rely on -fgnu-tm of libstdc++ code for now (or at least we
tried to avoid this so far).  Therefore, the transactional clones in
this patch are all manually instrumented (ie, the functions are C
functions with names matching the mangled names of the respective C++
functions, and the _ZGTt prefix signaling that they are txnal clones).

Second, exceptions still use a COW string internally, which cannot be
made transaction-safe with just compiler support because of the
reference counting implementation inside of COW strings, which uses
atomics.  One would need something custom for that nonetheless.

Thus, the patch adds txnal clones as required.  They are new exported
symbols, but not visible to nontransactional code.  The only changes to
headers is transaction_safe[_dynamic] annotations where required by the
TS, and a few friend declarations.  The annotations are only enabled if
a user compiles with -fgnu-tm.  IOW, the changes are pretty much
invisible when not using the TM TS.

There are also commented-out calls to _ITM_setAssociatedException in the
code, which exist to show how we plan to support transaction
cancellation through exceptions (which needs some more libitm support
and bugfixes on the compiler side).

Tested on x86_64-linux and x86-linux.

OK?

2016-01-07  Torvald Riegel  <triegel@redhat.com>

	* include/bits/basic_string.h (basic_string): Declare friends.
	* include/bits/c++config (_GLIBCXX_TXN_SAFE,
	_GLIBCXX_TXN_SAFE_DYN, _GLIBCXX_USE_ALLOCATOR_NEW): New.
	* include/std/stdexcept (logic_error, domain_error, invalid_argument,
	length_error, out_of_range, runtime_error, range_error,
	underflow_error, overflow_error): Declare members as transaction-safe.
	(logic_error, runtime_error): Declare friend functions.
	* libsupc++/exception (exception, bad_exception): Declare members as
	transaction-safe.
	* src/c++11/cow-stdexcept.cc: Define transactional clones for the
	transaction-safe members of exceptions and helper functions.
	* libsupc++/eh_exception.cc: Adjust and define transactional clones.
	* config/abi/pre/gnu.ver (GLIBCXX_3.4.22) Add transactional clones.
	(CXXABI_1.3.10): New.
	* acinclude.m4 (GLIBCXX_CHECK_SIZE_T_MANGLING): New.
	(GLIBCXX_ENABLE_ALLOCATOR): Set ENABLE_ALLOCATOR_NEW.
	* configure.ac: Call GLIBCXX_CHECK_SIZE_T_MANGLING.
	* include/Makefile.am: Write ENABLE_ALLOCATOR_NEW to c++config.h.
	* include/Makefile.in: Regenerate.
	* config.h.in: Regenerate.
	* configure: Regenerate.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: tmts-safeexc.patch
Type: text/x-patch
Size: 39122 bytes
Desc: not available
URL: <http://gcc.gnu.org/pipermail/libstdc++/attachments/20160107/4c54cbc4/attachment.bin>