[PATCH] D54941: [clang-tidy] Ignore bool -> single bit bitfield conversion in readability-implicit-bool-conversion

[Alexander Kornienko via Phabricator via cfe-commits]

alexfh accepted this revision.
alexfh added a comment.
This revision is now accepted and ready to land.

LG



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Comment at: docs/clang-tidy/checks/readability-implicit-bool-conversion.rst:77-78
 
-- boolean expression/literal to integer,
+- boolean expression/literal to integer (conversion from boolean to a single
+  bit bitfield is explicitly allowed),
 
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malcolm.parsons wrote:
> aaron.ballman wrote:
> > I think it should only be allowed if the bit-field type is unsigned; signed bit-fields with a single bit are inherently not portable because you don't know if that bit represents a sign bit or a value bit (imagine a sign and magnitude integer representation).
> > 
> > C++20 is changing this by standardizing on two's complement, but earlier versions of C++ (and currently, all versions of C) are still impacted, so another approach is to gate this on the language standard mode that's in effect.
> I think it's the responsibility of a compiler using sign and magnitude representation to warn about signed single bit bitfields.
I agree with Malcolm's argument. But if the concern is practical (i.e. if there's a user of this check, who's working with such compiler), we can add an option to enable the warning in this case. Any objections?


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https://reviews.llvm.org/D54941