[cfe-dev] getting visit methods right

[Jordan Rose]

Write a static analyzer plugin instead.

The RecursiveASTVisitor interface is for syntactic checking; it won't be able to do a good job with propagating information forward with, say, loops. If you're looking for a "fast" flow-sensitive analysis, Sema's AnalysisBasedWarnings shows how it's done, but if you want more precision in actually determining which paths are feasible, you're going to need the full power of the static analyzer. You're basically reinventing the entire analyzer core if you're trying to track the flow of data from assignments to conditions and then to which branch is taken.

Unfortunately, the documentation on how to write a static analyzer "checker" is still a bit limited, but you can find information at http://clang-analyzer.llvm.org/checker_dev_manual.html and the slides from our talk at the LLVM Develeopers' Meeting at http://llvm.org/devmtg/2012-11/Zaks-Rose-Checker24Hours.pdf

Best,
Jordan


On Nov 27, 2012, at 1:24 , Rajendra <rks at cse.iitb.ac.in> wrote:

> Any suggestion on this topic, please?
> 
> - Rajendra
> 
> On 26-11-2012 03:21 PM, Rajendra wrote:
>> Hi,
>> 
>> I have overridden VisitIfStmt(Stmt* s) and some visit methods for
>> binary operators:
>> - VisitBinAssign(),
>> - VisitBinAdd() and other arithmetic operators,
>> - VisitBinGT() and other relational operators
>> 
>> My dilemma is how do I return from different visit methods (or call
>> them explicitly)
>> so that I can perform some analysis on binary operators and use them
>> in condition part,
>> then clause and else clause for IfStmt?  e.g. I want to analyze
>> following C program:
>> int main() {
>>    int x, y;
>>    x = 10;
>>    if (x > 0)
>>        y = 1;
>>    else if (x == 0)
>>        y = 0;
>>    else
>>        y = -1;
>>    return 0;
>> }
>> 
>> Basic block contains:
>>   1: int x;
>>   2: int y;
>>   3: x = 10
>>   4: x > 0
>>   T: if [B6.4]
>> 
>> Now, for condition x > 0 (line 3:) due to VisitBinGT() can get
>> following info:
>>        Relational Op >
>>        LHS identifier = x
>>        type: int
>>        RHS value: 0
>> From VisitIfStmt() I can get pointer to condition part, then and else
>> clauses.
>> so, how should I combine IfStmt and information I have due to visit
>> to other methods?
>> 
>> Please advise.
>> 
>> - Rajendra
> 
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