incubator-stdcxx-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Eric Lemings" <Eric.Lemi...@roguewave.com>
Subject RE: Another style question
Date Wed, 16 Apr 2008 19:23:10 GMT
 

> -----Original Message-----
> From: Martin Sebor [mailto:msebor@gmail.com] On Behalf Of Martin Sebor
> Sent: Wednesday, April 16, 2008 12:33 PM
> To: dev@stdcxx.apache.org
> Subject: Re: Another style question
> 
...
> 
> As with every other convention, we're not 100% consistent, only
> about 90% by my count.

Strictly speaking though, the #ifdef and #ifndef directives are
redundant; i.e. `#ifdef foo` and `#if defined foo` are exactly
the same but only the latter form permits compound expressions
(e.g. `#if defined foo || defined bar`).

> Btw., a more flexible way to code these workarounds would have been
> to code it like so:
> 
>    #if !_RWSTD_NO_MEMBER_TEMPLATES
>        // correct code
>    #else
>        // workaround
>    #endif
> 
> This way, each config macro could be #defined on the command line
> to 0 or 1 to toggle either branch (e.g., for testing and debugging).
> That's not possible with the #ifndef approach.

>From a natural language perspective, I've always found the double
negatives (e.g. `#ifndef _RWSTD_NO_FOO) a bit irritating but that's
just me.

> 
> Incidentally, speaking of #ifdefs, the other convention is to
> add a comment after the #else and #endif directives mentioning
> the name of the macro(s) used in the conditional (or some such
> text) to help see which which branch is active. So according
> to this convention the code above would look like so:
> 
>    #ifndef _RWSTD_NO_MEMBER_TEMPLATES
>        // correct code
>    #else   // ifdef (_RWSTD_NO_MEMBER_TEMPLATES)
>        // workaround
>    #endif   // _RWSTD_NO_MEMBER_TEMPLATES

Yep.  I use this convention myself though I find applying it
unilaterally can be overkill in certain circumstances (e.g.
when there's lots of non-nested #if-#else blocks consisting
of only 5 lines each) but I do it anyway for consistency.

Brad.

Mime
View raw message