[cfe-dev] How to get global variables' SymbolRef?

[Jordan Rose]

The first thing is that there are a couple of things wrong with your plan: global variables have regions, not symbols, and the state of memory is modeled by the Store, not the Environment. checkASTDecl is for syntactic checks, not path-sensitive ones, so of course the globals have no value.

What you actually need depends a lot on what sort of analysis you’re doing. If you’re trying to verify the initial values of global variables, you can use checkASTDecl and the normal constant-evaluation functions in the AST library. If you’re trying to check the state of all global variables at a particular time…that’s a bit harder, but I’m almost sure you don’t need it. (Why does your checker care about errno, for example?) So, what check are you trying to implement?

I also recommend you read through the Checker Developer Manual at http://clang-analyzer.llvm.org/checker_dev_manual.html, or watch the talk linked from there, for a firm grounding in the design of the analyzer and component classes.

Best,
Jordan


On Nov 11, 2013, at 22:58 , edward jiamu <edwardjiamu at gmail.com> wrote:

> Hi:
>    I want to record all the global variables' SymbolRef for analysis. Try
> the following ways, but failed.
> 
>   1) void check::checkPreStmt(const DeclStmt *DS, CheckerContext &C) const;
>       only contains the local variables of the analysed function
> 
>   2) void check::checkASTDecl(const VarDecl *TU, AnalysisManager& mgr,
>                    BugReporter &BR) const
>      contains the global variables, but no CheckerContext info. so can not
> convert it to SVal as usual:
> 
>      ProgramStateRef state = C.getState();
>      SVal sv = state->getSVal(...);
>      SymbolRef Sym = sv.getAsSymbol();
> 
>   3) depends on "state", how to get the "state" corresponding to the global
> variables?
>    Environment env = state->getEnvironment();
>    for(Environment::iterator it = env.begin(); it != env.end(); ++it)
>    {
>        SVal sv = it->second;
>        //...
>    }
> 
>    is there correct way?
> 
> Best Regards.
> 
> Jiamu      
> 
> 
> 
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