[cfe-commits] r89773 - in /cfe/trunk: lib/CodeGen/CGStmt.cpp lib/CodeGen/CodeGenFunction.h test/CodeGenCXX/condition.cpp

[Daniel Dunbar]

On Mon, Nov 30, 2009 at 11:52 AM, Douglas Gregor <dgregor at apple.com> wrote:
>
> On Nov 30, 2009, at 11:48 AM, Daniel Dunbar wrote:
>
>> Hi Doug,
>>
>> On Tue, Nov 24, 2009 at 8:43 AM, Douglas Gregor <dgregor at apple.com> wrote:
>>>
>>> Author: dgregor
>>> Date: Tue Nov 24 10:43:22 2009
>>> New Revision: 89773
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=89773&view=rev
>>> Log:
>>> Introduce cleanup scopes for "if" statements in two places:
>>>  - Outside the "if", to ensure that we destroy the condition variable
>>>   at the end of the "if" statement rather than at the end of the
>>>   block containing the "if" statement.
>>
>> Yay!
>>
>>>  - Inside the "then" and "else" branches, so that we emit then- or
>>>   else-local cleanups at the end of the corresponding block when the
>>>   block is not a compound statement.
>>
>> I can't convince myself these are necessary. Cleanups are run in FIFO
>> order so how is this different than putting them on the cleanup for
>> the containing statement, since no code is run after the then/else
>> branches terminate.
>
>
> It's for disgusting cases like:
>
>        if (rand() % 2 == 1)
>          std::string s = "foo";
>        std::string t = "bar";
>
> so that we destroy "s" after the if statement but before "t", but only if we
> took the "then" branch.

Right, I follow that, but there is a cleanup scope around the if
statement itself, so the cleanups for s can still go there and still
be run before t, no?

 - Daniel