| Message ID | 153616289529.23468.7498785670556620808.stgit@warthog.procyon.org.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [01/11] UAPI: drm: Fix use of C++ keywords as structural members | expand |
On Wed, Sep 05, 2018 at 04:54:55PM +0100, David Howells wrote: > The virtio_net_ctrl_hdr struct uses a C++ keyword as structural members. Fix > this by inserting an anonymous union that provides an alternative name and > then hide the reserved name in C++. > > Signed-off-by: David Howells <dhowells@redhat.com> > cc: "Michael S. Tsirkin" <mst@redhat.com> > cc: Jason Wang <jasowang@redhat.com> > cc: virtualization@lists.linux-foundation.org > --- > > include/uapi/linux/virtio_net.h | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h > index a3715a3224c1..967142bc0e05 100644 > --- a/include/uapi/linux/virtio_net.h > +++ b/include/uapi/linux/virtio_net.h > @@ -150,7 +150,12 @@ struct virtio_net_hdr_mrg_rxbuf { > * command goes in between. > */ > struct virtio_net_ctrl_hdr { > - __u8 class; > + union { > +#ifndef __cplusplus > + __u8 class; > +#endif > + __u8 _class; > + }; Ugh, ick, no! Come on now, either put the whole C namespace stuff around the file, or don't care about this at all. Doing this whack-a-mole style is a mess. "class" is a fine variable name for C code, there's no reason this has to change here at all. greg k-h
Greg KH <gregkh@linuxfoundation.org> wrote: > Come on now, either put the whole C namespace stuff around the file, You mean wrap it with 'extern "C" { ... }'? That doesn't fix it. That only affects the symbols generated by the compiler. > "class" is a fine variable name for C code, there's no reason this has > to change here at all. I'm trying to prevent future accidents like the one in linux/keyctl.h. The easiest way to do this[**] is to pass the entire set of UAPI headers[*] through the compiler together. Besides I still have my dark plan to C++-ise the kernel[***] :-D David [*] with some obvious exceptions [**] and it catches other errors too [***] https://lkml.org/lkml/2018/4/1/116
On Wed, Sep 05, 2018 at 04:54:55PM +0100, David Howells wrote: > The virtio_net_ctrl_hdr struct uses a C++ keyword as structural members. Fix > this by inserting an anonymous union that provides an alternative name and > then hide the reserved name in C++. > > Signed-off-by: David Howells <dhowells@redhat.com> > cc: "Michael S. Tsirkin" <mst@redhat.com> > cc: Jason Wang <jasowang@redhat.com> > cc: virtualization@lists.linux-foundation.org > --- > > include/uapi/linux/virtio_net.h | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h > index a3715a3224c1..967142bc0e05 100644 > --- a/include/uapi/linux/virtio_net.h > +++ b/include/uapi/linux/virtio_net.h > @@ -150,7 +150,12 @@ struct virtio_net_hdr_mrg_rxbuf { > * command goes in between. > */ > struct virtio_net_ctrl_hdr { > - __u8 class; > + union { > +#ifndef __cplusplus > + __u8 class; > +#endif > + __u8 _class; > + }; > __u8 cmd; > } __attribute__((packed)); As long as you do not intend to use any classes, how about simply adding -Dclass=_class to your command line? Seems to work fine with gcc 8.1.1 on Fedora.
Michael S. Tsirkin <mst@redhat.com> wrote: > As long as you do not intend to use any classes, how about > simply adding > > -Dclass=_class > > to your command line? That kind of misses the point;-). It's not reasonable to expect all userspace C++ users to do this. David
On Thu, Sep 06, 2018 at 08:09:19AM +0100, David Howells wrote: > Michael S. Tsirkin <mst@redhat.com> wrote: > > > As long as you do not intend to use any classes, how about > > simply adding > > > > -Dclass=_class > > > > to your command line? > > That kind of misses the point;-). It's not reasonable to expect all userspace > C++ users to do this. > > David I thought one of the points was that building kernel with c++ catches some bugs, no? If the point is to make life easier for c++ userspace I'm not sure what we can do to be frank. C++ seems to be adding new keywords with no restraint (C99 did it with inline and restrict too, but it seems this stopped) so no good way to future-proof code for all language dialects. So I'd like to know which are the actual c++ users asking for this - we can then accomodate the specific version they need. Meanwhile people can get by with a wrapper along the lines of #define class _class #include <linux/virtio_net.h> #undef class
diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h index a3715a3224c1..967142bc0e05 100644 --- a/include/uapi/linux/virtio_net.h +++ b/include/uapi/linux/virtio_net.h @@ -150,7 +150,12 @@ struct virtio_net_hdr_mrg_rxbuf { * command goes in between. */ struct virtio_net_ctrl_hdr { - __u8 class; + union { +#ifndef __cplusplus + __u8 class; +#endif + __u8 _class; + }; __u8 cmd; } __attribute__((packed));
The virtio_net_ctrl_hdr struct uses a C++ keyword as structural members. Fix this by inserting an anonymous union that provides an alternative name and then hide the reserved name in C++. Signed-off-by: David Howells <dhowells@redhat.com> cc: "Michael S. Tsirkin" <mst@redhat.com> cc: Jason Wang <jasowang@redhat.com> cc: virtualization@lists.linux-foundation.org --- include/uapi/linux/virtio_net.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)