[PATCH] D44231: [clang-tidy] Check for sizeof that call functions

Aaron Ballman via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Thu Mar 8 08:05:20 PST 2018

aaron.ballman added a comment.

In https://reviews.llvm.org/D44231#1031380, @pfultz2 wrote:

> > Can you elaborate a bit more about this?
> This catches problems when calling `sizeof(f())` when `f` returns an integer(or enum). This is because, most likely, the integer represents the type to be chosen, however, `sizeof` is being computed for an integer and not the type the integer represents. That is, the user has an enum for the `data_type`:
>   enum data_type {
>       float_type,
>       double_type
>   };
> At some point the user may call a function to get the data type(perhaps `x.GetType()`) and pass it on to `sizeof`, like `sizeof(x.GetType())`, which is incorrect.

Can you point to some real world code that would benefit from this check? I don't see this as being a common issue with code and I am concerned about false positives. For instance, it's reasonable to write `sizeof(func_call())` in a context where you don't want to repeat the type name in multiple places. I've seen this construct used in LLVM's code base (see Prologue::getLength() in DWARFDebugLine.h for one such instance).

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