Re: C++ PATCH for c++/48370 (extending lifetime of temps in aggregate initialization)

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Tue, Jun 12, 2012 at 10:00 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Thu, Nov 3, 2011 at 8:50 PM, Jason Merrill <jason@redhat.com> wrote:
>> 12.2 states that a temporary bound to a reference lives as long as the
>> reference itself.  We have done that for reference variables, but not in
>> other cases, such as aggregate initialization of a struct with reference
>> members.  In C++11, elements of a std::initializer_list have the same
>> semantics; they live as long as the std::initializer_list.  Again, we were
>> implementing that for initializer_list variables but not for
>> initializer_list subobjects.  This patch fixes that.
>>
>> Furthermore, if a temporary's lifetime is extended, we need to also extend
>> the lifetimes of any temporaries bound to references in its initializer, and
>> so on.
>>
>> The patch introduces a function extend_ref_init_temps called from
>> store_init_value after the call to digest_init.  To expose elements of an
>> initializer_list to this function, I needed to stop using
>> build_aggr_init_full_exprs for aggregate initialization of arrays, and
>> consequently needed to call build_vec_init from store_init_value to use one
>> EH region for cleaning up the whole array rather than one per element.  To
>> deal with multiple extended temporaries, we need to change the cleanup
>> pointer from a single tree to a VEC, and add a discriminator to the mangled
>> name of reference init temporaries; this has no ABI impact, since the
>> temporaries have no linkage, but I also updated the demangler accordingly.
>>
>> Since we now do lifetime extension in extend_ref_init_temps, we can
>> drastically simplify initialize_reference and do away with
>> build_init_list_var_init.
>>
>> Tested x86_64-pc-linux-gnu, applying to trunk.
>
> This caused:
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53650
>

This also caused:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54197

-- 
H.J.