--- a/configure.ac	Sat May 04 17:37:47 2024 +0200
+++ b/configure.ac	Sat May 04 19:10:03 2024 +0200
@@ -93,7 +93,7 @@
 fi
 LIBS="$LIBS -lm"
 
-AC_CHECK_DECLS(gettid,result=yes,result=no)
+AC_CHECK_FUNC(gettid,result=yes,result=no)
 if test "$result" = "yes"; then
   AC_DEFINE(HAVE_GETTID)
 fi