[Qemu-commits] [qemu/qemu] c4e9dd: net/vhost-vdpa.c: Fix clang compilation failure

[Peter Maydell]

  Branch: refs/heads/staging
  Home:   https://github.com/qemu/qemu
  Commit: c4e9ddef97b07bdab222fb5cc1246f54357c5e87
      
https://github.com/qemu/qemu/commit/c4e9ddef97b07bdab222fb5cc1246f54357c5e87
  Author: Peter Maydell <peter.maydell@linaro.org>
  Date:   2022-10-31 (Mon, 31 Oct 2022)

  Changed paths:
    M net/vhost-vdpa.c

  Log Message:
  -----------
  net/vhost-vdpa.c: Fix clang compilation failure

Commit 8801ccd0500437 introduced a compilation failure with clang
version 10.0.0-4ubuntu1:

../../net/vhost-vdpa.c:654:16: error: variable 'vdpa_device_fd' is
used uninitialized whenever 'if' condition is false
[-Werror,-Wsometimes-uninitialized]
    } else if (opts->has_vhostfd) {
               ^~~~~~~~~~~~~~~~~
../../net/vhost-vdpa.c:662:33: note: uninitialized use occurs here
    r = vhost_vdpa_get_features(vdpa_device_fd, &features, errp);
                                ^~~~~~~~~~~~~~
../../net/vhost-vdpa.c:654:12: note: remove the 'if' if its condition
is always true
    } else if (opts->has_vhostfd) {
           ^~~~~~~~~~~~~~~~~~~~~~~
../../net/vhost-vdpa.c:629:23: note: initialize the variable
'vdpa_device_fd' to silence this warning
    int vdpa_device_fd;
                      ^
                       = 0
1 error generated.

It's a false positive -- the compiler doesn't manage to figure out
that the error checks further up mean that there's no code path where
vdpa_device_fd isn't initialized.  Put another way, the problem is
that we check "if (opts->has_vhostfd)" when in fact that condition
must always be true.  A cleverer static analyser would probably warn
that we were checking an always-true condition.

Fix the compilation failure by removing the unnecessary if().

Fixes: 8801ccd0500437 ("vhost-vdpa: allow passing opened vhostfd to vhost-vdpa")
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20221031132901.1277150-1-peter.maydell@linaro.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>