[cfe-dev] [StaticAnalyzer] How to suppress bug reports when a checker reached a noreturn function

[Haowei Wu via cfe-dev]

Hi Gábor,

This setting helps. But I have a follow up question. Is it possible to
treat return from 'int main(int argc, char* argv[])' as a sink just like
the [[noreturn]] functions?

For example, like the previous example,

typedef uint32_t mx_handle_t;
typedef int32_t mx_status_t;

mx_status_t mx_channel_create(
uint32_t options,
mx_handle_t* out0,
mx_handle_t* out1);

int main(int argc, char* argv[]) {
  mx_handle_t sa, sb;
  mx_channel_create(0, &sa, &sb);
  //...
  return 0;
}

The program will quit if it returns from main and it would not be very
helpful to report these leaks as well.

Thanks,
Haowei

On Tue, Aug 1, 2017 at 2:55 AM, Gábor Horváth <xazax.hun at gmail.com> wrote:

> Hi Haowei!
>
> There is a heuristic already in the analyzer to suppress such cases. There
> is a method in BugType called setSuppressOnSink. Could you check if setting
> this to true would help?
>
> Regards,
> Gábor
>
>
>
> On 31 July 2017 at 19:51, Haowei Wu via cfe-dev <cfe-dev at lists.llvm.org>
> wrote:
>
>> Hi,
>>
>> I am working on a checker and I would like to suppress bug reports when a
>> path reached a function with [[noreturn]] attribute. For example:
>>
>> typedef uint32_t mx_handle_t;
>> typedef int32_t mx_status_t;
>>
>> mx_status_t mx_channel_create(
>> uint32_t options,
>> mx_handle_t* out0,
>> mx_handle_t* out1);
>>
>> [[noreturn]] void noreturnFunc();
>>
>> void checkNoReturn() {
>>   mx_handle_t sa, sb;
>>   mx_channel_create(0, &sa, &sb);
>>   //...
>>   noreturnFunc();
>> }
>>
>> Function mx_channel_create will allocate two handles(file descriptors)
>> and save them to 'sa' and 'sb'. Since there is no other call to release
>> these two handles, the checker will report them as leaked. But in this
>> special case, there is a call to 'noreturnFunc()' which will terminate
>> the process and leaked handles will be recycled by the OS so it is may not
>> necessary to report these bugs. The source code of the checker can be found
>> in D35968, D36022, D36023, D36024.
>>
>> My first thought is that I can use REGISTER_TRAIT_WITHPROGRAMSTATE macro
>> to add a bool flag in the ProgramState and this flag will be set if the
>> FunctionDecl->isNoReturn() returns true in the evalCall callback. Then
>> in the checkDeadSymbols callback, do not report any leaked symbols if
>> the flag registered through REGISTER_TRAIT_WITHPROGRAMSTATE is set.
>> However, I did some experiment and found out that in the code example, the
>> symbols in 'sa' and 'sb' were dead in the checkDeadSymbols before the
>> evalCall on 'noreturnFunc' was invoked. Further experiment showed that
>> the checkDeadSymbols on 'sa' and 'sb' was invoked even before checkPreStmt(const
>> CallExpr *, CheckerContext &) callback. So this solution does not work.
>>
>> Is there anything I can do in the checker to solve this problem?
>>
>> Thanks for any help.
>>
>> Haowei
>>
>> _______________________________________________
>> cfe-dev mailing list
>> cfe-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>
>>
>
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