[cfe-dev] how to track a stack var with static analyzer

[Anna Zaks]

> On Apr 16, 2015, at 8:00 AM, Alexander Droste <alexander.ra.droste at googlemail.com> wrote:
> 
> Hi everyone,
> 
> I'm trying to track a stack variable using the static analyzer
> by getting a symbol from function args.
> 
> In checkPostCall I do:
> 
> if (callEvent.getCalleeIdentifier() == IdentInfoTrackMem) {
>    // ...
>    auto s = callEvent.getArgSVal(0).getAsSymbol();
>    if (s == nullptr) {
>        std::cout << "nullptr" << std::endl;
>    }
> }
> 
> // this is function used to track the var
> void trackMem(int *i) {
>    *i = 0;
>    printf("%i\n", *i);
> }
> 
> 
> The strange thing is that it workes fine when the variable passed to
> trackMem is previously allocated with malloc. But when passing
> a pointer to a stack variable to trackMem callEvent.getArgSVal(0).getAsSymbol() always evaluates to nullptr.

The address of a stack variable is not a symbol. Take a look at this section of the Checker Developer Manual and examine the SVal that represents the 0-th argument.

http://clang-analyzer.llvm.org/checker_dev_manual.html#values <http://clang-analyzer.llvm.org/checker_dev_manual.html#values>

> 
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