Re: Moving to C11? (was Re: Redefinition of typedefs (C11 feature))

[Thomas Huth]

On 11/09/2020 22.06, Eduardo Habkost wrote:
> On Fri, Sep 11, 2020 at 08:06:10PM +0100, Peter Maydell wrote:
>> On Fri, 11 Sep 2020 at 19:49, Eduardo Habkost <ehabkost@redhat.com> wrote:
>>>
>>> I'm wondering: do our supported build host platforms all include
>>> compilers that are new enough to let us redefine typedefs?
>>>
>>> The ability to redefine typedefs is a C11 feature which would be
>>> very useful for simplifying our QOM boilerplate code.  The
>>> feature is supported by GCC since 2011 (v4.6.0)[1], and by clang
>>> since 2012 (v3.1)[2].
>>
>> In configure we mandate either GCC v4.8 or better, or
>> clang v3.4 or better, or XCode Clang v5.1 or better
>> (Apple uses a different version numbering setup to upstream).
>> So you should probably double-check that that xcode clang has
>> what you want, but it looks like we're good to go otherwise.
> 
> Can anybody confirm if the following is accurate?
> 
> https://gist.github.com/yamaya/2924292#file-xcode-clang-vers-L67
> # Xcode 5.1 (5B130a)
> Apple LLVM version 5.1 (clang-503.0.38) (based on LLVM 3.4svn)
> Target: x86_64-apple-darwin13.1.0
> Thread model: posix
> 
> If we know we have GCC 4.8+ or clang 3.4+, can we move to C11 and
> start using -std=gnu11?

You don't have to switch to gnu11, redefintions of typedefs are already
fine in gnu99, they are a gnu extension there to the c99 standard.

See also:
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=7be41675f7cb16b

https://www.mail-archive.com/qemu-devel@nongnu.org/msg585581.html

 HTH,
  Thomas