On 09/29/2015 11:27 PM, Jason Merrill wrote:
On 09/29/2015 08:34 PM, Richard Smith wrote:
On 29 September 2015 at 11:09, Jason Merrill <[email protected]> wrote:
The Transactional Memory TS introduces "transaction-safe function"
types,
which are distinct from non-transaction-safe function types, though the
former converts to the latter. So we need to represent this in
mangling.
I think no change to mangling of actual functions is necessary, since
functions that differ only in their tx-qualifier cannot be overloaded.
I thought the intent was that we'd emit two function bodies for a
transaction-safe function definition (one for the case where we are
inside
an atomic block, another for the case where we are not). Do we also
need a
new function mangling for the former case?
Yes, I thought I had mentioned that in a follow-up, but evidently not.
GCC currently mangles the transaction entry point as
<special_name> ::= GTt <encoding>
So we only need to worry about function types.
One possibility for handling it would be to add a qualifier 'T' after
the
<ref-qualifier> at the end of <function-type>, but that complicates the
ambiguity between these qualifiers and parameter types.
I think my preference is to make it a normal type qualifier, perhaps
using "Dx", so void (*)() transaction_safe becomes "PDxFvvE".
There's also the question of whether the non-transaction-safe function
type is substitutable in this mangling. I think we might as well allow
it, as we do for cv-qualified types.
We also need to add a __transaction_safe_mask to
__pbase_type_info::__masks so that exception handlers can perform the
transaction safety conversion.
Would you also use the same __function_type_info for the pointee type in
typeid(void (*)() transaction_safe) and typeid(void(*)())? That seems
like
an odd fit for the language semantics ("transaction_safe" is part of the
function type, not a layer on top of it like cv-qualifiers are), but
necessary if we want the exception handler to be able to efficiently
check
for a match.
Right. This seemed simpler to me than adding a new
__tx_safe_function_type_info class.
Jason
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