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Subject: Re: [std-proposals] Allow [[deprecated]] on call site to disable deprecated warning
From: Avi Kivity (avi_at_[hidden])
Date: 2021-02-07 07:45:58


On 07/02/2021 13.37, Andrey Semashev via Std-Proposals wrote:
> On February 7, 2021 1:22:41 PM Avi Kivity via Std-Proposals
> <std-proposals_at_[hidden]> wrote:
>
>> On 28/01/2021 13.34, Ville Voutilainen via Std-Proposals wrote:
>>> On Thu, 28 Jan 2021 at 13:06, Dominic Fandrey via Std-Proposals
>>> <std-proposals_at_[hidden]> wrote:
>>>> I recently ran into this issue:
>>>>
>>>> 1. Marked a set of legacy methods [[deprecated]]
>>>> 2. Unit tests no longer compile (we run -Wall -Werror of course)
>>>>
>>>> Of course I don't want to get rid of the unit tests before I get
>>>> rid of the
>>>> functions. So I was faced with two choices:
>>>>
>>>> 1. Create #ifdef #pragma soup for all 3 compilers that we use
>>>> 2. Remove [[deprecated]]
>>>>
>>>> The #ifdef #pragma soup needs to be updated every time a compiler
>>>> is added,
>>>> and it bloats the code and makes unit tests more difficult to read.
>>>> So I
>>>> went for option 2. As long as I cannot ignore [[deprecated]] in a
>>>> portable
>>>> manner I cannot use it.
>>>>
>>>> So my suggestion is:
>>>>
>>>> ```
>>>> [[deprecated("use: std::optional<std::size_t> size()")]]int
>>>> size(std::size_t & size);
>>>>
>>>>
>>>> bool test_size() {
>>>>  std::size_t s{0};
>>>>  return 0 == [[deprecated]]size(s) && s != 0;
>>>> }
>>> Create your own MY_DEPRECATED macro, make it expand to actual
>>> deprecation normally, but not in unit tests,
>>> compile the unit tests with -DMY_SOMETHING that disables deprecations.
>>> Or just add a #define into
>>> your unit tests.
>>
>>
>> Doesn't that break with modules?
>>
>>
>> We should not be suggesting solutions that involve the preprocessor
>> in 2021.
>
> I don't think that preprocessor is deprecated or its proper use should
> be judged or anything. A preprocessor based solution is fine if this
> tool is best fit for the job.
>
>
>

It does not work with modules. If I have a module that has a
[[deprecated]] declaration, no amount of preprocessor tricks in the
importing code will affect that declaration.


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