llvm dev - Mar 2014 - [LLVMdev] [RFC] The coding standard for "struct" should be relaxed or removed

The current guidelines [1] on the use of the struct keyword are too
restrictive and apparently ignored.  They limit the use of struct to
PODs, citing broken compilers.

The guidelines are out-of-date and should be relaxed.  Here’s why:

 1. Our updated list of supported compilers should all deal correctly
    with non-POD structs.

 2. A quick grep of the source suggests that no one paid attention
    anyway.

I’ve attached a patch that removes the guideline entirely (matching
the apparent current practice), but does anyone feel a new explicit
guideline is in order?

[1]: http://llvm.org/docs/CodingStandards.html#use-of-class-and-struct-keywords

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On Sat, Mar 1, 2014 at 5:59 PM, Duncan P. N. Exon Smith <
dexonsmith at apple.com> wrote:
> The current guidelines [1] on the use of the struct keyword are too
> restrictive and apparently ignored.  They limit the use of struct to
> PODs, citing broken compilers.
>
> The guidelines are out-of-date and should be relaxed.  Here’s why:
>
>  1. Our updated list of supported compilers should all deal correctly
>     with non-POD structs.
>
>  2. A quick grep of the source suggests that no one paid attention
>     anyway.
>
> I’ve attached a patch that removes the guideline entirely (matching
> the apparent current practice), but does anyone feel a new explicit
> guideline is in order?
>
We should at least remove it, the rule is nonsense as you point out.

I would be happy to have a soft rule along the lines of "use struct for
types which are intended to be aggregate types, or to behave like aggregate
types". IE, types which are suitable for use with list-initialization in
C++11.

I also don't feel terribly strongly about such things other than that I
would prefer *some* guidance to lessen the inconsistency.
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On Mar 1, 2014, at 7:15 PM, Chandler Carruth <chandlerc at google.com>
wrote:
> On Sat, Mar 1, 2014 at 5:59 PM, Duncan P. N. Exon Smith <dexonsmith at
apple.com> wrote:
> The current guidelines [1] on the use of the struct keyword are too
> restrictive and apparently ignored.  They limit the use of struct to
> PODs, citing broken compilers.
> 
> The guidelines are out-of-date and should be relaxed.  Here’s why:
> 
>  1. Our updated list of supported compilers should all deal correctly
>     with non-POD structs.
> 
>  2. A quick grep of the source suggests that no one paid attention
>     anyway.
> 
> I’ve attached a patch that removes the guideline entirely (matching
> the apparent current practice), but does anyone feel a new explicit
> guideline is in order?
> 
> We should at least remove it, the rule is nonsense as you point out.
This rule was specifically about brokenness with some version of MSVC.  That
version (I have no idea which, or if it still does that) mangled classes and
structs differently.  If this isn't the case for the currently supported
version of MSVC, we should definitely remove this guideline.

-Chris

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