qemu-kvm-1.0.1 compilation error on Ubuntu 12.04

[Whit Blauvelt]

  CC libhw64/9pfs/virtio-9p-handle.o
/usr/src/qemu-kvm-1.0.1/hw/9pfs/virtio-9p-handle.c: In function ‘handle_update_file_cred’:
/usr/src/qemu-kvm-1.0.1/hw/9pfs/virtio-9p-handle.c:70:58: error: ‘AT_EMPTY_PATH’ undeclared (first use in this function)
/usr/src/qemu-kvm-1.0.1/hw/9pfs/virtio-9p-handle.c:70:58: note: each undeclared identifier is reported only once for each function it appears in
/usr/src/qemu-kvm-1.0.1/hw/9pfs/virtio-9p-handle.c: In function ‘handle_lstat’:
/usr/src/qemu-kvm-1.0.1/hw/9pfs/virtio-9p-handle.c:87:34: error: ‘AT_EMPTY_PATH’ undeclared (first use in this function)
/usr/src/qemu-kvm-1.0.1/hw/9pfs/virtio-9p-handle.c: In function ‘handle_symlink’:
/usr/src/qemu-kvm-1.0.1/hw/9pfs/virtio-9p-handle.c:314:62: error: ‘AT_EMPTY_PATH’ undeclared (first use in this function)
/usr/src/qemu-kvm-1.0.1/hw/9pfs/virtio-9p-handle.c: In function ‘handle_link’:
/usr/src/qemu-kvm-1.0.1/hw/9pfs/virtio-9p-handle.c:337:45: error: ‘AT_EMPTY_PATH’ undeclared (first use in this function)
/usr/src/qemu-kvm-1.0.1/hw/9pfs/virtio-9p-handle.c: In function ‘handle_chown’:
/usr/src/qemu-kvm-1.0.1/hw/9pfs/virtio-9p-handle.c:373:58: error: ‘AT_EMPTY_PATH’ undeclared (first use in this function)
make[1]: *** [9pfs/virtio-9p-handle.o] Error 1
make: *** [subdir-libhw64] Error 2

It compiled okay on 11.04.

[Serge Hallyn (serge-hallyn)]

The bug is actually in libc (see bug 1010069). You can work around it using the same patch we are using in the ubuntu package, define_AT_EMPTY_PATH.patch. It probably won't apply cleanly upstream, but just make sure to add

#ifndef AT_REMOVEDIR
#define AT_REMOVEDIR 0x200
#endif
#ifndef AT_EMPTY_PATH
#define AT_EMPTY_PATH 0x1000 /* Allow empty relative pathname */
#endif
#ifndef O_PATH
#define O_PATH 010000000
#endif

near the top of hw/9pfs/virtio-9p-handle.c

[Serge Hallyn (serge-hallyn)]

Oh, actually I was about to mark this invalid, but in fact it is a valid bug that it is trying to compile this bit of code when the AT* were not defined. There is a patch sent and acked upstream to fix this, so I'll mark it confirmed for now.

[Serge Hallyn (serge-hallyn)]

(Note, the patch has Subject:

Subject: [Qemu-devel] [PATCH] configure: Fix build for some versions of
        glibc (9pfs)
)

[Peter Maydell (pmaydell)]

The patch Serge mentions was committed upstream and released last year.