[PATCH] [StaticAnalyzer] New checker Sizeof on expression

[Jordan Rose]

Sorry for letting this slip through the cracks! I know it's now been a month and a half, but what were the false positives you saw without the HasSideEffects check? For example:

+int SizeofFunctionCallExpression() {
+  return sizeof(SizeofDefine() - 1);
+} // no-warning

This should have a warning, since the function is not called. If it interferes with the VLA thing Aaron brought up, though...

I never got a response to this:

> +    if (Binop->getLHS()->getType()->isArrayType() ||
> +        Binop->getLHS()->getType()->isAnyPointerType() ||
> +        Binop->getRHS()->getType()->isArrayType() ||
> +        Binop->getRHS()->getType()->isAnyPointerType())
> +      return;

> 
> I don't think this is correct...the user is only trying to get ptrdiff_t if both the LHS and RHS are pointer-ish.

Finally, how about using an extra set of parens to silence the warning? It's harder to typo, and we have some precedent for that. 

Jordan


On May 13, 2014, at 3:27 , Anders Rönnholm <Anders.Ronnholm at evidente.se> wrote:

> Pinging
> ________________________________________
> Från: Anders Rönnholm
> Skickat: den 27 mars 2014 11:09
> Till: Jordan Rose
> Cc: cfe-commits at cs.uiuc.edu; Daniel Marjamäki
> Ämne: SV: [PATCH] [StaticAnalyzer] New checker Sizeof on expression
> 
> New patch with new diagnostic message. I couldn't come up with a better wording so i'm using your suggestion. I don't know of a good way to silence the warning.
> 
> I removed the check for HasSideEffects previously but had to take back.  I noticed that the patch triggered some false positives without it.
> 
> //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: Jordan Rose [jordan_rose at apple.com]
> Skickat: den 31 januari 2014 18:50
> Till: Anders Rönnholm
> Cc: cfe-commits at cs.uiuc.edu; Daniel Marjamäki
> Ämne: Re: [PATCH] [StaticAnalyzer] New checker Sizeof on expression
> 
> Sorry to have let this slip! This is looking good, but I had one more thought about the diagnostic message. It says "may yield unexpected results", but doesn't really explain what those unexpected results are. I was wondering if we could work the type into the message for the operator case.
> 
> "operand of sizeof is a binary expression of type %0, which may not be intended"
> 
> I don't like that wording either, but at least this one makes people say "what? why isn't it [the type I actually want]?". Also, should there be a way to silence the warning?
> 
> What do you think?
> Jordan
> 
> 
> On Jan 23, 2014, at 6:40 , Anders Rönnholm <Anders.Ronnholm at evidente.se<mailto:Anders.Ronnholm at evidente.se>> wrote:
> 
> Hi,
> 
> New one with comments handled.
> 
> ________________________________________
> Från: Jordan Rose [jordan_rose at apple.com<mailto:jordan_rose at apple.com>]
> Skickat: den 20 december 2013 19:15
> Till: Anders Rönnholm
> Cc: cfe-commits at cs.uiuc.edu<mailto:cfe-commits at cs.uiuc.edu>; Daniel Marjamäki; Anna Zaks; David Blaikie; Richard Smith; Matt Calabrese
> Ämne: Re: [PATCH] [StaticAnalyzer] New checker Sizeof on expression
> 
> On Dec 10, 2013, at 4:38 , Anders Rönnholm <Anders.Ronnholm at evidente.se<mailto:Anders.Ronnholm at evidente.se><mailto:Anders.Ronnholm at evidente.se>> wrote:
> 
> Are you OK to commit this patch or do you see more issues?
> 
> I'm not sure if anyone else has ideological concerns. There's always a flag to turn this off, I suppose.
> 
> 
> +  if (S.isSFINAEContext())
> +      return;
> 
> Code style: extra indent?
> 
> 
> +  if(E->HasSideEffects(S.getASTContext()))
> +    return;
> 
> sizeof doesn't evaluate its argument, so I'm not sure why you wouldn't want to warn here.
> 
> 
> +  const FunctionDecl *FD = S.getCurFunctionDecl();
> +  if(FD && FD->isFunctionTemplateSpecialization())
> +    return;
> 
> Code style: space after if. (Above too, actually.)
> 
> 
> +    if (Binop->getLHS()->getType()->isArrayType() ||
> +        Binop->getLHS()->getType()->isAnyPointerType() ||
> +        Binop->getRHS()->getType()->isArrayType() ||
> +        Binop->getRHS()->getType()->isAnyPointerType())
> +      return;
> 
> I don't think this is correct...the user is only trying to get ptrdiff_t if both the LHS and RHS are pointer-ish.
> 
> 
> +def warn_sizeof_bin_op : Warning<
> +  "using sizeof() on an expression with an operator may yield unexpected results">,
> +  InGroup<SizeofOnExpression>;
> +
> +def warn_sizeof_sizeof : Warning<
> +  "using sizeof() on sizeof() may yield unexpected results.">,
> +  InGroup<SizeofOnExpression>;
> +
> 
> sizeof doesn't actually require parens, so we shouldn't put the parens in the diagnostics.
> 
> <sizeofonexpression.diff>

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