Re: [Qemu-devel] [PATCH 4/7] compiler: add macro for GCC weak symbols

[Blue Swirl]

On Fri, Jul 27, 2012 at 3:31 PM, Anthony Liguori <address@hidden> wrote:
> Peter Maydell <address@hidden> writes:
>
>> On 27 July 2012 15:27, Anthony Liguori <address@hidden> wrote:
>>> Peter Maydell <address@hidden> writes:
>>>> The GCC manual says "Weak symbols are supported for ELF targets,
>>>> and also for a.out targets when using the GNU assembler and linker".
>>>> Have you tested this on Windows and MacOSX ?
>>>
>>> Weak symbols are supposed to be supported by mingw32.
>>>
>>> I have no idea about MacOS X.
>>>
>>> I have no way to develop or test for MacOS X using free software so I
>>> honestly don't care about it.
>>
>> My approach to this is to avoid non-standard things
>
> http://en.wikipedia.org/wiki/C99#Implementations
>
> So unless you plan on compiling QEMU with xlc, pgi, or icc, I don't
> think relying on "standard things" really helps.

LLVM/Clang should definitely be in the plan.

>
> QEMU doesn't support C99, it supports GCC.  There's no point in
> debating about whether we should rely on extensions or not.  We already
> do--extensively.

Not so extensively. There are a few extensions for which there is no
simple alternative (like QEMU_PACKED) but other compilers likely need
similar extensions. Then there are other extensions (like :? without
middle expression) which can be easily avoided. We should avoid to use
the non-standard extensions whenever possible.

>
> Regards,
>
> Anthony Liguori
>
>
>> -- if I
>> write a patch which is pretty much standard C then it's the
>> platform's problem if it mishandles it. If I write a patch
>> that uses a compiler-specific or OS-specific thing then I
>> have to also provide the relevant alternatives...so I try
>> to avoid doing that :-)
>>
>> -- PMM
>
>