Wine 5.0.4 regression: build failure in dlls/qcap/v4l.c

[Gerald Pfeifer]

The following patch (full version at the end)

    commit cb8e15a64307e580123b459e4c5964dc7b0d73d9
    Author: Huw D. M. Davies <huw at codeweavers.com>
    Date:   Tue Dec 22 14:26:36 2020 +0000

        qcap: Avoid unused variable warning if v4l is absent.

broke builds of Wine 5.0.4 where v4l is not present, specifically when 
the header <linux/videodev2.h> is not available.

Configuring with --without-v4l2 does not trigger this; it really is
about the presence of the header.

The failure mode is 

  In file included from v4l.c:60:
  v4l.c: In function 'qcap_driver_destroy':
  ../../include/wine/debug.h:485:56: error: '__wine_dbch___default' undeclared (first use in this function)
  :
  v4l.c:602:5: note: in expansion of macro 'ERR'
    602 |     ERR("v4l absent: shouldn't be called\n"); \
        |     ^~~
  v4l.c:607:5: note: in expansion of macro 'FAIL_WITH_ERR'
    607 |     FAIL_WITH_ERR;
        |     ^~~~~~~~~~~~~

and the straightforward fix is simply reverting this patch.
 
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=254601 has more details.

Gerald


commit cb8e15a64307e580123b459e4c5964dc7b0d73d9
jAuthor: Huw D. M. Davies <huw at codeweavers.com>
Date:   Tue Dec 22 14:26:36 2020 +0000

    qcap: Avoid unused variable warning if v4l is absent.
    
    Signed-off-by: Huw Davies <huw at codeweavers.com>
    Signed-off-by: Zebediah Figura <z.figura12 at gmail.com>
    Signed-off-by: Alexandre Julliard <julliard at winehq.org>
    (cherry picked from commit 73281bf132e1dad9aebf3410b21616727438fb63)
    Signed-off-by: Michael Stefaniuc <mstefani at winehq.org>

diff --git a/dlls/qcap/v4l.c b/dlls/qcap/v4l.c
index 0d7e176d3da..e548000187f 100644
--- a/dlls/qcap/v4l.c
+++ b/dlls/qcap/v4l.c
@@ -63,10 +63,9 @@
 #include "qcap_main.h"
 #include "capture.h"
 
-WINE_DEFAULT_DEBUG_CHANNEL(qcap);
-
 #ifdef HAVE_LINUX_VIDEODEV2_H
 
+WINE_DEFAULT_DEBUG_CHANNEL(qcap);
 WINE_DECLARE_DEBUG_CHANNEL(winediag);
 
 static typeof(open) *video_open = open;