On 13/09/2020 04.51, Eduardo Habkost wrote: > On Sat, Sep 12, 2020 at 08:45:19AM +0200, Thomas Huth wrote: >> 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 <ehabk...@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 > > They still trigger a warning with gnu99 on clang: > > $ clang --version > clang version 10.0.0 (Fedora 10.0.0-2.fc32) > Target: x86_64-unknown-linux-gnu > Thread model: posix > InstalledDir: /usr/bin > $ cat test.c > typedef struct A A; > typedef struct A A; > $ clang -std=gnu11 -c test.c > $ clang -std=gnu99 -c test.c > test.c:2:18: warning: redefinition of typedef 'A' is a C11 feature > [-Wtypedef-redefinition] > typedef struct A A;
Ah, right, I forgot about that ... so for clang, we silence that warning via CFLAGS in the configure script. See commit e6e90feedb706b1. Thomas