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Re: New warnings on emacs-26 branch with gcc 8.2.0

From: Andy Moreton
Subject: Re: New warnings on emacs-26 branch with gcc 8.2.0
Date: Sat, 18 Aug 2018 20:07:20 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (windows-nt)

On Sat 18 Aug 2018, Eli Zaretskii wrote:

>> From: Bruno Haible <address@hidden>
>> Date: Sat, 18 Aug 2018 18:09:27 +0200
>> Cc: Paul Eggert <address@hidden>, Andy Moreton <address@hidden>,
>>      address@hidden
>> So, there are 4 options:
>>   1) Use static reference to Windows API functions.
>>   2) Use '#pragma GCC diagnostic ignored "-Wcast-function-type"'
>>   3) Remove -Wcast-function-type from the compiler options.
>>   4) Live with the warning.
>> I'm opposed to 1), since it removes either features or portability.
>> I could do 2), but it does not feel like the right thing, to silence
>> a compiler warning when the user has explicitly requested a warning.
>> So, please choose among 3) and 4).
> There's also this additional option:
>   5) Cast through (void *).  Like this:
>       GetSystemTimePreciseAsFileTimeFunc =
>         (GetSystemTimePreciseAsFileTimeFuncType) (void (*) (void)) 
> GetProcAddress (kernel32, "GetSystemTimePreciseAsFileTime");

This is the sensible option. GetProcAddress returns FARPROC, so there is
no way of performing this cast correctly without some sort of type

The additional (void (*) (void)) cast deliberately suppresses the warning
in this case, which still allowing use of the warning to catch abuse of
function pointer types in other parts of the program.


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