diff -Nrup a/configure b/configure
--- a/configure	2006-09-20 16:34:03.000000000 -0600
+++ b/configure	2019-12-19 06:07:54.302627575 -0700
@@ -11959,7 +11959,7 @@ cat >>conftest.$ac_ext <<_ACEOF
 /* end confdefs.h.  */
 
 #include <malloc.h>
-int test1() {
+__attribute__ ((used)) int test1() {
     return _alloca(42);
 }
 
diff -Nrup a/configure.ac b/configure.ac
--- a/configure.ac	2006-05-03 08:10:36.000000000 -0600
+++ b/configure.ac	2019-12-19 06:07:27.468727400 -0700
@@ -451,7 +451,7 @@ dnl Visual C++ doesn't have alloca, does
 AC_CACHE_CHECK(for _alloca, ac_cv_c__alloca,
 [AC_TRY_LINK([
 #include <malloc.h>
-int test1() {
+__attribute__ ((used)) int test1() {
     return _alloca(42);
 }
 ],