Issue #13415: Test in configure if unsetenv() has a return value or not.
diff --git a/configure.in b/configure.in
index 1bbb559..81de0d4 100644
--- a/configure.in
+++ b/configure.in
@@ -2696,6 +2696,15 @@
[AC_MSG_RESULT(no)
])
+AC_MSG_CHECKING(for broken unsetenv)
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+#include <stdlib.h>
+]], [[int res = unsetenv("DUMMY")]])],
+ [AC_MSG_RESULT(no)],
+ [AC_DEFINE(HAVE_BROKEN_UNSETENV, 1, Define if `unsetenv` does not return an int.)
+ AC_MSG_RESULT(yes)
+])
+
dnl check for true
AC_CHECK_PROGS(TRUE, true, /bin/true)