[cfe-dev] How can I get a FieldRegion in a CompoundAssignOperator in Static Analyzer?

[Arthur Yoo]

Thank you, Jordan. I'm doing a checker to analyze C programs. Maybe I have
to transform the CompoundAssignOperator to AssignOperator manually before
analysis.


2014/1/23 Jordan Rose <jordan_rose at apple.com>

> Ah, interesting. That's unfortunate: we need to load from the LHS, but
> that overwrites the location value stored in that expression. Please file a
> bug; since the value can always be recovered from the location, we should
> prefer to leave that available for checkers to access. (They'd have to be
> careful, though, since the LHS could be a C++ reference.)
>
> I'm not completely sure *how* we'll do this, but it'd be good to have
> this in the system. The relevant code is in ExprEngine::VisitBinaryOperator
> and its call to evalLoad.
>
> A note on terminology: both locations and pure values are represented with
> SVals, and pointer values are usually region values. The C++ standard uses
> the term "lvalue" (or "glvalue") for addresses of memory regions (which can
> be loaded from or stored to), and "rvalue" for what you've been calling
> "SVal" (the contents of a region). You could use "location" vs. "value" if
> you want to avoid "lvalue" and "rvalue".
>
> Jordan
>
>
> On Jan 21, 2014, at 21:33 , Arthur Yoo <phjy007 at gmail.com> wrote:
>
> Hi Jordan,
>
> When evaluating a BinaryAssignOperator(*obj.a = 1;*), if I use *state->getSVal(LHS,
> C.getLocationContext())*, I will get the SVal of LHS, which actually is a
> MemRegionVal. So I can get LHS's MemRegion via MemRegionVal. However, for
> my test code snippet above, I've tried to use *state->getSVal(LHS,
> C.getLocationContext())* to get the SVal of LHS when evaluating '*obj.a
> += sizeof(long);*' in *void checkPostStmt(const BinaryOperator *Op,
> CheckerContext &C) const, *the Analyzer gave me '0 S32b'. I know that '0
> S32b' does be the value for obj.a. But I want to get the FieldRegion of obj.a,
> not its SVal. However, I don't know how to get its FieldRegion when
> evaluating a CompoundAssignOperator.
>
>
> 2014/1/22 Jordan Rose <jordan_rose at apple.com>
>
>>
>> On Jan 21, 2014, at 5:19 , Arthur Yoo <phjy007 at gmail.com> wrote:
>>
>> Hi all,
>>
>>
>> I want to get a FieldRegion when evaluating a CompoundAssignOperator.
>> The code snippet for my test is like below:
>>
>>
>> typedef struct {
>>
>>            int a;
>>
>>            int *p;
>>
>> } Obj;
>>
>> Obj obj;
>>
>> obj.a = 0;
>>
>> obj.a += sizeof(long);
>>
>>
>> When evaluating the statement ‘*obj.a += sizeof(long);*’ in the method *void
>> checkPostStmt(const BinaryOperator *Op, CheckerContext &C) const*, I
>> want to get the FieldRegion of *obj.a*. But I don’t know how to get it.
>> Is there anyone can provide me a way to get *obj.a*’s FieldRegion?
>> Thanks a lot.
>>
>>
>> Hi, Arthur. The value of the BinaryOperator's LHS should be an SVal
>> representing the FieldRegion. Are you not seeing that?
>>
>> Jordan
>>
>
>
>
> --
> Best regards,
> Arthur Yoo
>
>
>


-- 
Best regards,
岳佳圆 | Yue Jiayuan | Arthur Yoo
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-dev/attachments/20140123/9915e88e/attachment.html>