Re: [libvirt] [Qemu-devel] [PATCH 4/7] compiler: add macro for GCC weak symbols
On Fri, Jul 27, 2012 at 3:31 PM, Anthony Liguori <aliguori(a)us.ibm.com> wrote:
Peter Maydell <peter.maydell(a)linaro.org> writes:
> On 27 July 2012 15:27, Anthony Liguori <aliguori(a)us.ibm.com> wrote:
>> Peter Maydell <peter.maydell(a)linaro.org> 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