[PATCH] [StaticAnalyzer] New checker Sizeof on expression
Jordan Rose
jordan_rose at apple.com
Mon Oct 7 09:55:36 PDT 2013
I'm fine with this staying in the analyzer for now, unless David, Richard, or Eli feel it should be a warning right away.
+ if (isa<BinaryOperator>(ArgExpr->IgnoreParens())) {
+ const BinaryOperator *Binop =
+ dyn_cast<BinaryOperator>(ArgExpr->IgnoreParens());
Conventionally we'd combine these two in the if-condition itself (see the LLVM Programmer's Manual). You never need to follow isa<> with a checked dyn_cast<>, either.
+ BR.EmitBasicReport(AC->getDecl(),
+ "Expression with an operation in sizeof()",
+ categories::LogicError,
+ "Using sizeof() on an expression with an operator "
+ "may yield unexpected results.", ELoc, &R, 1);
There's already an overload that takes a single range; please use that instead of a count of 1.
+ if (LeftSizeof && RightSizeof) {
+ if (LeftSizeof->getKind() == UETT_SizeOf &&
+ RightSizeof->getKind() == UETT_SizeOf)
+ return false;
+ }
I haven't written a RecursiveASTVisitor in a while, but the documentation seems to say that returning false will abort the entire traversal, not just skip the current node's children. Is that correct? (Please add a test case.)
Have you run this over real code? Has it found any bugs?
Jordan
On Oct 4, 2013, at 6:09 , Anders Rönnholm <Anders.Ronnholm at evidente.se> wrote:
> Hi,
>
> As i have understood it you aren't sure whether to put the checker in the compiler right away or analyzer so i let it stay in the analyzer to be evaluated. I guess it should be implemented as a warning eventually.
>
> I have added a check to report when sizeof is called inside a sizeof.
> sizeof(sizeof(int))
>
> I also made an exception when compared against another sizeof as suggested.
>
> //Anders
>
> .......................................................................................................................
> Anders Rönnholm Senior Engineer
> Evidente ES East AB Warfvinges väg 34 SE-112 51 Stockholm Sweden
>
> Mobile: +46 (0)70 912 42 54
> E-mail: Anders.Ronnholm at evidente.se
>
> www.evidente.se
>
> ________________________________________
> Från: David Blaikie [dblaikie at gmail.com]
> Skickat: den 26 september 2013 04:31
> Till: Jordan Rose
> Cc: Anders Rönnholm; Richard Smith; Eli Friedman; cfe-commits at cs.uiuc.edu
> Ämne: Re: [PATCH] [StaticAnalyzer] New checker Sizeof on expression
>
> On Wed, Sep 25, 2013 at 6:39 PM, Jordan Rose <jordan_rose at apple.com<mailto:jordan_rose at apple.com>> wrote:
> Seems reasonable. This is something that we could also implement as a compiler warning, though. David, Richard, Eli, what do you think: compiler or analyzer?
>
> personally I think anything cheap enough to do at compile time probably should be, but Doug's general attitude has been that the other prerequisite is bug-finding capability; Essentially if a warning would be too noisy to be on by default in an existing codebase (because it caused more busy work than bug fixing to cleanup the codebase to be warning-free) then it doesn't go in the compiler
>
> Putting it in the analyzer would then seem an unfortunate side-effect of its true/false positive rate.
>
> Of course we're still missing the middle ground: things that don't have the true positive rate to be intrinsic features of the compiler, but a codebase may want to opt-in to if the bug-finding is acceptable to them. This would come in the form of a Clang plugin, ideally, but we don't have an authoritative/configurable plugin for this purpose yet.
>
>
>
> Comments on the patch itself:
>
> + return sizeof(2 + 1); // expected-warning{{Sizeof() on an expression with an operator may yield unexpected results}}
>
> The rule that capitalizes analyzer output (unlike compiler warnings) makes this look very strange. Maybe it's worth inserting the word "Using" before "sizeof".
>
>
> +//==- CheckSizeofOnExpression.cpp - Check expressions in sizeof() *- C++ -*-==//
>
> The format header "-*- C++ -*-" needs all those dashes and stars to be recognized. However, since this is a .cpp file, you should just leave it out anyway and uses dashes to fill the empty space -----==//
>
>
> +//
> +// This file defines a check for expressions made in sizeof()
> +//
>
> Please turn this into a Doxygen file comment. http://llvm.org/docs/CodingStandards.html#file-headers
>
>
> +class WalkAST : public StmtVisitor<WalkAST> {
>
> Other checkers predate RecursiveASTVisitor, but you might as well use RecursiveASTVisitor and avoid writing the VisitChildren boilerplate. This would also handle checking C++ constructor initializers, which aren't actually part of the body of the constructor. (We should probably migrate all the old walkers to RecursiveASTVisitor for this reason.)
>
>
> + Expr *Expr = E->getArgumentExpr();
>
> We try not to shadow type names with local variable names, which I know is a bit trickier when variable names are also capitalized. Also, there's no reason not to make this a pointer to const.
>
>
> + //Only check binary operators
>
> + // is expression based on macro => don't warn
>
> Please use complete sentences for comments, including a space after the //.
>
>
> + BR.EmitBasicReport(AC->getDecl(),
> + "Expression with an operation in sizeof()",
> + "Logic",
> + "Sizeof() on an expression with an operator "
> + "may yield unexpected results.",
> + ELoc, &R, 1);
>
> The bug categories aren't well-defined, but there's already one called "Logic error" that's used by some of the analyzer core checkers. It might be nice to refactor this, SizeofPointerChecker, and BuiltinBug to share a single new constant in CommonBugCategories.{h,cpp}.
>
> Also, there's an overload that takes a single SourceRange. (Double-also, BugReporter should just be using ArrayRef, which autoconverts from a single element anyway.)
>
>
> + walker.Visit(D->getBody());
>
> If you do change to RecursiveASTVisitor, make sure you visit D, to include the constructor initializers.
>
> Thanks for working on this!
> Jordan
>
>
> On Sep 20, 2013, at 2:37 , Anders Rönnholm <Anders.Ronnholm at evidente.se<mailto:Anders.Ronnholm at evidente.se>> wrote:
>
>> Hi,
>>
>> Sorry I broke a test with a last minute change.
>>
>> Thanks,
>> Anders
>>
>> .......................................................................................................................
>> Anders Rönnholm Senior Engineer
>> Evidente ES East AB Warfvinges väg 34 SE-112 51 Stockholm Sweden
>>
>> Mobile: +46 (0)70 912 42 54<tel:%2B46%20%280%2970%20912%2042%2054>
>> E-mail: Anders.Ronnholm at evidente.se<mailto:Anders.Ronnholm at evidente.se>
>>
>> www.evidente.se<http://www.evidente.se>
>>
>> ________________________________________
>> Från: Anders Rönnholm
>> Skickat: den 20 september 2013 11:19
>> Till: cfe-commits at cs.uiuc.edu<mailto:cfe-commits at cs.uiuc.edu>
>> Ämne: Re: [PATCH] [StaticAnalyzer] New checker Sizeof on expression
>>
>> Hi,
>>
>> I forgot that there is i line limit of 80, i have corrected that.
>>
>> //Anders
>>
>> .......................................................................................................................
>> Anders Rönnholm Senior Engineer
>> Evidente ES East AB Warfvinges väg 34 SE-112 51 Stockholm Sweden
>>
>> Mobile: +46 (0)70 912 42 54<tel:%2B46%20%280%2970%20912%2042%2054>
>> E-mail: Anders.Ronnholm at evidente.se<mailto:Anders.Ronnholm at evidente.se>
>>
>> www.evidente.se<http://www.evidente.se>
>>
>> ________________________________________
>> Från: Anders Rönnholm
>> Skickat: den 20 september 2013 10:23
>> Till: cfe-commits at cs.uiuc.edu<mailto:cfe-commits at cs.uiuc.edu>
>> Ämne: [PATCH] [StaticAnalyzer] New checker Sizeof on expression
>>
>> Hi,
>>
>> I have another checker i would like to get reviewed. It checks for usage of sizeof on an expression. For now it only checks binary operators. Sizeof on defines does not generate a warning.
>>
>> Example:
>> sizeof(2 + 1);
>>
>> Thanks,
>> Anders
>>
>> .......................................................................................................................
>> Anders Rönnholm Senior Engineer
>> Evidente ES East AB Warfvinges väg 34 SE-112 51 Stockholm Sweden
>>
>> Mobile: +46 (0)70 912 42 54<tel:%2B46%20%280%2970%20912%2042%2054>
>> E-mail: Anders.Ronnholm at evidente.se<mailto:Anders.Ronnholm at evidente.se>
>>
>> www.evidente.se<http://www.evidente.se>
>
>> _______________________________________________
>> cfe-commits mailing list
>> cfe-commits at cs.uiuc.edu<mailto:cfe-commits at cs.uiuc.edu>
>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
>
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