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

[Gábor Horváth via cfe-dev]

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
>
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>
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