[cfe-dev] Static analyzer question on how to tell if a Decl is a particular c++ function, or a particular class

[Aleksei Sidorin via cfe-dev]

Hello Li,

What you're doing is mostly fine. I can only add some potentially useful 
info inline.

14.02.2018 23:04, Li Kan via cfe-dev пишет:
> Hi folks,
>
> If this is not the correct mailing list for this question, please let 
> me know.
You're in the right place. Welcome :)

> I am trying to write a static analyzer for code base of my current 
> job. The particular static analyzer I am writing involves a particular 
> class of my company's code base. Let's say it is T. I want to write a 
> checker to ensure T.ok() is called before T.value() is called.
>
> Static analyzer is perfect for this type of check as it requires path 
> sensitive checks. When I trying to write the checker, I basically 
> checks for pre-call and post-call. I want to tell if a CallEvent is 
> T.ok() and T.value(). Currently what I am doing is:
> 1. From CallEvent, I cast to CXXMemberCall, and getOriginExpr(), then 
> call getMethodDecl().
You can also try to do the following chain: 
dyn_cast_or_null<CXXMethodDecl>(CallEvent.getDecl()) to obtain 
CXXMethodDecl.

> 2. From CXXMethodDecl, I first call getThisType(), then call 
> getAsCXXRecordDecl(), then getQualifiedNameAsString(), and compare 
> with qualified name of T, to make sure it is member of T.
To obtain parent class declaration from CXXMethodDecl, you can use 
getParent() method. So, the pseudocode will look like 
"MethodDecl->getParent()->getQualifiedNameAsString()".

> 3. From CXXMethodDecl, I call getNameAsString() to get the method 
> name, and compare them with "ok" and "value".
This looks OK. But it can be useful to know that 
getQualifiedNameAsString() for CXXMethodDecl will also include parent 
name. So, you can just check if MethodDecl->getQualifiedNameAsString() 
is equal to "T::value" or "T::ok".

> It works, but it looks complicated, and involves string comparison, 
> which I assume is slow. Is there a easier way, blessed by clang static 
> analyzer official teams, that tell if a MethodDecl, or CXXRecordDecl, 
> is the function or class I am interested in?
>
> The ideal way is, there is one-time call to lookup the MethodDecl for 
> T::ok() and T::value(), and CXXRecordDecl for T. Then ever since then, 
> I just need to compare the pointers.
This is possible. You can just launch a simple matcher against AST:
cxxMethodDecl(hasName("::T::value"))
and get CXXMethodDecl you need and compare with it later.

> Another way is, the first time I found it is T, T::ok() or T::value(), 
> I save the pointer of CXXRecordDecl or MethodDecl, and use the 
> pointers later. Is this the reliable (assume I use the pointer 
> canonical decl will not change) and blessed way to do it? If it is, is 
> my steps above the correct and simplest way to determine it is T::ok 
> or T::value? Is there some better and more reliable way?
I think it is reliable enough: pointers to canonical declarations don't 
change in AST.
>
> Thanks.
>
>
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-- 
Best regards,
Aleksei Sidorin,
SRR, Samsung Electronics

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