make error: implicit declaration of function ‘kill’

[hlb-schmidt]

error:

$> make
CC xmpl.c
xmpl.c: In function ‘xmpl_event_spawn’:
xmpl.c:1408:3: warning: implicit declaration of function ‘kill’ [-Wimplicit-function-declaration]
 1408 |   kill(pid, SIGKILL);
      |   ^~~~
xmpl.c:1408:13: error: ‘SIGKILL’ undeclared (first use in this function)
 1408 |   kill(pid, SIGKILL);
      |             ^~~~~~~
xmpl.c:1408:13: note: each undeclared identifier is reported only once for each function it appears in
make: *** [Makefile:107: xmpl.o] Error 1

possible fix:

$> git diff
diff --git a/xmpl.h b/xmpl.h
index 6424c52..febfc16 100644
--- a/xmpl.h
+++ b/xmpl.h
@@ -16,6 +16,7 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <xcb/xcb.h>
+#include <signal.h>
 //#include <xcb/xcb_icccm.h>
 
 const static u_int32_t XMPL_EVENT_MASK_NULL =