The -Wextra flag bundle gained a new warning -Wcast-function-type.
This complains if you cast between two function prototypes where
the number of parameters or their data types are not compatible.
Unfortunately we need such "bad" function casts for our event
callbacks. It is possible to silence the warning by first casting
to the generic "void (*)(void)" function prototype, but that is
rather ugly to add throughout libvirt code.

Signed-off-by: Daniel P. Berrangé <>
 m4/virt-compile-warnings.m4 | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/m4/virt-compile-warnings.m4 b/m4/virt-compile-warnings.m4
index 918764d36..fc185aef3 100644
--- a/m4/virt-compile-warnings.m4
+++ b/m4/virt-compile-warnings.m4
     # So we have -W enabled, and then have to explicitly turn off...
     wantwarn="$wantwarn -Wno-sign-compare"
+    # We do "bad" function casts all the time for event callbacks
+    wantwarn="$wantwarn -Wno-cast-function-type"
     # GNULIB expects this to be part of -Wc++-compat, but we turn
     # that one off, so we need to manually enable this again

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