libnm: suppress "-Warray-bounds" warning in nm_team_link_watcher_new_ethtool()

gcc-11.0.0-0.7.fc34 warns here:

    CC       libnm-core/libnm_core_la-nm-setting-team.lo
  libnm-core/nm-setting-team.c: In function ‘nm_team_link_watcher_new_ethtool’:
  libnm-core/nm-setting-team.c:127:33: error: array subscript ‘NMTeamLinkWatcher[0]’ is partly outside array bounds of ‘unsigned char[16]’ [-Werror=array-bounds]
    127 |     watcher->ref_count          = 1;
        |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
  libnm-core/nm-setting-team.c:125:15: note: referencing an object of size 16 allocated by ‘g_malloc’
    125 |     watcher = g_malloc(nm_offsetofend(NMTeamLinkWatcher, ethtool));
        |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  libnm-core/nm-setting-team.c:128:33: error: array subscript ‘NMTeamLinkWatcher[0]’ is partly outside array bounds of ‘unsigned char[16]’ [-Werror=array-bounds]
    128 |     watcher->type               = LINK_WATCHER_ETHTOOL;
        |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
  libnm-core/nm-setting-team.c:125:15: note: referencing an object of size 16 allocated by ‘g_malloc’
    125 |     watcher = g_malloc(nm_offsetofend(NMTeamLinkWatcher, ethtool));
        |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  libnm-core/nm-setting-team.c:129:33: error: array subscript ‘NMTeamLinkWatcher[0]’ is partly outside array bounds of ‘unsigned char[16]’ [-Werror=array-bounds]
    129 |     watcher->ethtool.delay_up   = delay_up;
        |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~
  libnm-core/nm-setting-team.c:125:15: note: referencing an object of size 16 allocated by ‘g_malloc’
    125 |     watcher = g_malloc(nm_offsetofend(NMTeamLinkWatcher, ethtool));
        |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  libnm-core/nm-setting-team.c:130:33: error: array subscript ‘NMTeamLinkWatcher[0]’ is partly outside array bounds of ‘unsigned char[16]’ [-Werror=array-bounds]
    130 |     watcher->ethtool.delay_down = delay_down;
        |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
  libnm-core/nm-setting-team.c:125:15: note: referencing an object of size 16 allocated by ‘g_malloc’
    125 |     watcher = g_malloc(nm_offsetofend(NMTeamLinkWatcher, ethtool));
        |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Maybe we should not use this trick and just malloc() a struct of the
intended size, however:

 - the code below does a similar thing, doing it differently for ethtool
   watcher is confusing.

 - the NMTeamLinkWatcher is a union which cannot alter its type. In no
   case is it correct to access the fields of the wrong union type. By
   allocating a smaller chunk, valgrind might catch such bugs.
   Also, NMTeamLinkWatcher's definition is private to the C source file,
   in no case must anybody assume that the rest of the buffer actually
   exists.

Hence, workaround the warning by suppressing it.

1 files changed, 4 insertions, 0 deletions

diff --git a/libnm-core/nm-setting-team.c b/libnm-core/nm-setting-team.c
index e4eb72a3b7..4f8e9a4cc6 100644
--- a/libnm-core/nm-setting-team.c
+++ b/libnm-core/nm-setting-team.c
@@ -122,6 +122,8 @@ nm_team_link_watcher_new_ethtool(int delay_up, int delay_down, GError **error)
         return NULL;
     }
 
+    NM_PRAGMA_WARNING_DISABLE("-Warray-bounds")
+
     watcher = g_malloc(nm_offsetofend(NMTeamLinkWatcher, ethtool));
 
     watcher->ref_count          = 1;
@@ -129,6 +131,8 @@ nm_team_link_watcher_new_ethtool(int delay_up, int delay_down, GError **error)
     watcher->ethtool.delay_up   = delay_up;
     watcher->ethtool.delay_down = delay_down;
 
+    NM_PRAGMA_WARNING_REENABLE
+
     return watcher;
 }