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Date: Wed, 19 Feb 2025 08:50:02 -0800
From: Andre Muezerie <andremue@linux.microsoft.com>
To: Morten =?iso-8859-1?Q?Br=F8rup?= <mb@smartsharesystems.com>
Cc: dev@dpdk.org, Chengwen Feng <fengchengwen@huawei.com>,
 stephen@networkplumber.org
Subject: Re: [PATCH v2 01/10] eal: add workaround for __builtin_constant_p
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On Tue, Feb 18, 2025 at 06:12:04PM +0100, Morten Brørup wrote:
> > From: Andre Muezerie [mailto:andremue@linux.microsoft.com]
> > Sent: Tuesday, 18 February 2025 17.32
> > 
> > There's no MSVC equivalent for compiler extension __builtin_constant_p.
> > EAL already had __rte_constant which was used as a first attempt to
> > workaround __builtin_constant_p when using MSVC. However, there are
> > pieces of code that would benefit from being able to provide a default
> > value to be used instead of it being always 0 like how it was done by
> > __rte_constant.
> > 
> > A new macro is added here allowing such default to be provided by the
> > caller.
> 
> NAK to the new macro.
> 
> Please use the sizeof() hack suggested by Stephen to provide an implementation of __rte_constant(e) for MSVC.
> Here's a link to an example of the hack:
> https://news.ycombinator.com/item?id=16720172

Thanks for the link. I tried to use the hack as suggested but turns out it does
not work with msvc. It results in error C2100: "you cannot dereference an
operand of type 'void'".

I'm open to further suggestions.