[PATCH] Proposal on how to fix temporary dtors.

[Jordan Rose]

Ah...then I'm glad we added the assertion. :-) Lifetime-extended temporaries aren't quite implemented correctly yet, but we should probably be removing or not even adding the state when the temporary is lifetime-extended.

Unfortunately I don't have this paged in, but there's logic in processing auto destructors to handle this, and a bug (http://llvm.org/bugs/show_bug.cgi?id=19539) about how it's wrong.

Jordan


On Jul 7, 2014, at 13:13 , Manuel Klimek <klimek at google.com> wrote:

> Sigh. That triggers in Analysis/dtor.cpp for this CXXBindTemporaryExpr:
> CXXBindTemporaryExpr 0x3c195d8 'class LifetimeExtension::SaveOnVirtualDestruct' (CXXTemporary 0x3c195d0)
> `-CXXTemporaryObjectExpr 0x3c19590 'class LifetimeExtension::SaveOnVirtualDestruct' 'void (void)'
> 
> I assume something fishy is going on for lifetime extended temporaries...
> 
> 
> On Mon, Jul 7, 2014 at 8:38 PM, Jordan Rose <jordan_rose at apple.com> wrote:
> 
> On Jul 7, 2014, at 11:37 , Manuel Klimek <klimek at google.com> wrote:
> 
>> On Mon, Jul 7, 2014 at 8:05 PM, Jordan Rose <jordan_rose at apple.com> wrote:
>> 
>> On Jul 7, 2014, at 10:50 , Manuel Klimek <klimek at google.com> wrote:
>> 
>>> On Mon, Jul 7, 2014 at 7:42 PM, Jordan Rose <jordan_rose at apple.com> wrote:
>>> 
>>> On Jul 7, 2014, at 10:41 , Manuel Klimek <klimek at google.com> wrote:
>>> 
>>>> On Mon, Jul 7, 2014 at 7:38 PM, Jordan Rose <jordan_rose at apple.com> wrote:
>>>> 
>>>> On Jul 7, 2014, at 10:37 , Manuel Klimek <klimek at google.com> wrote:
>>>> 
>>>>> On Mon, Jul 7, 2014 at 7:29 PM, Jordan Rose <jordan_rose at apple.com> wrote:
>>>>> 
>>>>> On Jul 7, 2014, at 10:28 , Manuel Klimek <klimek at google.com> wrote:
>>>>> 
>>>>>> On Mon, Jul 7, 2014 at 6:48 PM, Jordan Rose <jordan_rose at apple.com> wrote:
>>>>>> Can you add an assertion at the end of a block that there are no outstanding temporary destructors in the current stack frame? That seems useful.
>>>>>> 
>>>>>> Do you mean at the end of a VisitBlockDecl?
>>>>> 
>>>>> No, during the path-sensitive run, so handleBlockExit.
>>>>> 
>>>>> So you mean at the end of a CFG block? But here we might have outstanding temporary dtors open (?) 
>>>> 
>>>> Oops, right. Was thinking too much in terms of AST structure. How about at the end of a function (inlined or not)?
>>>> 
>>>> Could we say every time we transition from a block with a temp dtor terminator to a block that does not have a temp dtor terminator (or an unconditional terminator) we check?
>>> 
>>> That sounds correct, but misses the case where we built the CFG wrong (forgetting to add the branch in the correct place and thus never getting to the temp dtor block at all).
>>> 
>>> Makes sense. Do you have a hint where the right place on function exit to check it would be? :)
>> 
>> *checks* ExprEngine::processEndOfFunction.
>> 
>> Hm, so we'll need to adjust the data structure to be indexed by stack frame somehow (use a map) instead of the pair<expr, stack-frame>?
> 
> Eh, since it's an assertion I'd be fine with just iterating over it in a helper function. Or better, using std::find_if (if it has proper begin/end members).
> 

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