diff --git a/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_GETENV.h b/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_GETENV.h
new file mode 100644
index 0000000..6b91c6b
--- /dev/null
+++ b/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_GETENV.h
@@ -0,0 +1,18 @@
+// HAVE_GETENV : BUILD2_AUTOCONF_LIBC_VERSION
+
+#ifndef BUILD2_AUTOCONF_LIBC_VERSION
+#  error BUILD2_AUTOCONF_LIBC_VERSION appears to be conditionally included
+#endif
+
+#undef HAVE_GETENV
+
+/* Since Version 7 AT&T UNIX, 4.3BSD-Tahoe (OpenBSD, FreeBSD, NetBSD, Mac OS X),
+* glibc 1.09
+ */
+#if defined(__FreeBSD__)            || \
+    defined(__OpenBSD__)            || \
+    defined(__NetBSD__)             || \
+    defined(BUILD2_AUTOCONF_MACOS)  || \
+    BUILD2_AUTOCONF_GLIBC_PREREQ(1, 09)
+#  define HAVE_GETENV 1
+#endif
diff --git a/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_GETRLIMIT.h b/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_GETRLIMIT.h
new file mode 100644
index 0000000..66de11b
--- /dev/null
+++ b/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_GETRLIMIT.h
@@ -0,0 +1,18 @@
+// HAVE_GETRLIMIT : BUILD2_AUTOCONF_LIBC_VERSION
+
+#ifndef BUILD2_AUTOCONF_LIBC_VERSION
+#  error BUILD2_AUTOCONF_LIBC_VERSION appears to be conditionally included
+#endif
+
+#undef HAVE_GETRLIMIT
+
+/* Since 4.2BSD (Linux, OpenBSD, FreeBSD, NetBSD, Mac OS X),
+ * glibc 1.90
+ */
+#if defined(__FreeBSD__)            || \
+    defined(__OpenBSD__)            || \
+    defined(__NetBSD__)             || \
+    defined(BUILD2_AUTOCONF_MACOS)  || \
+    BUILD2_AUTOCONF_GLIBC_PREREQ(1, 90)
+#  define HAVE_GETRLIMIT 1
+#endif
diff --git a/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_PUTENV.h b/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_PUTENV.h
new file mode 100644
index 0000000..921d8c0
--- /dev/null
+++ b/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_PUTENV.h
@@ -0,0 +1,18 @@
+// HAVE_PUTENV : BUILD2_AUTOCONF_LIBC_VERSION
+
+#ifndef BUILD2_AUTOCONF_LIBC_VERSION
+#  error BUILD2_AUTOCONF_LIBC_VERSION appears to be conditionally included
+#endif
+
+#undef HAVE_PUTENV
+
+/* Since AT&T System V Release 2 UNIX, 4.3BSD-Reno (OpenBSD, FreeBSD, NetBSD, Mac OS X),
+* glibc 1.09
+ */
+#if defined(__FreeBSD__)            || \
+    defined(__OpenBSD__)            || \
+    defined(__NetBSD__)             || \
+    defined(BUILD2_AUTOCONF_MACOS)  || \
+    BUILD2_AUTOCONF_GLIBC_PREREQ(1, 09)
+#  define HAVE_PUTENV 1
+#endif
diff --git a/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_SETENV.h b/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_SETENV.h
new file mode 100644
index 0000000..01edffd
--- /dev/null
+++ b/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_SETENV.h
@@ -0,0 +1,18 @@
+// HAVE_SETENV : BUILD2_AUTOCONF_LIBC_VERSION
+
+#ifndef BUILD2_AUTOCONF_LIBC_VERSION
+#  error BUILD2_AUTOCONF_LIBC_VERSION appears to be conditionally included
+#endif
+
+#undef HAVE_SETENV
+
+/* Since Version 7 AT&T UNIX, 4.3BSD-Tahoe (OpenBSD, FreeBSD, NetBSD, Mac OS X),
+ * glibc 1.09
+ */
+#if defined(__FreeBSD__)            || \
+    defined(__OpenBSD__)            || \
+    defined(__NetBSD__)             || \
+    defined(BUILD2_AUTOCONF_MACOS)  || \
+    BUILD2_AUTOCONF_GLIBC_PREREQ(1, 09)
+#  define HAVE_SETENV 1
+#endif
diff --git a/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_SETFD.h b/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_SETFD.h
new file mode 100644
index 0000000..9028ca3
--- /dev/null
+++ b/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_SETFD.h
@@ -0,0 +1,19 @@
+// HAVE_SETFD : BUILD2_AUTOCONF_LIBC_VERSION
+
+#ifndef BUILD2_AUTOCONF_LIBC_VERSION
+#  error BUILD2_AUTOCONF_LIBC_VERSION appears to be conditionally included
+#endif
+
+#undef HAVE_SETFD
+
+/* Since SVr4, 4.3BSD, POSIX.1-2001 (only Linux mentioned but assume all
+ * because it's old & standardized),
+ * glibc 1.90
+ */
+#if defined(__FreeBSD__)                || \
+    defined(__OpenBSD__)                || \
+    defined(__NetBSD__)                 || \
+    defined(BUILD2_AUTOCONF_MACOS)      || \
+    BUILD2_AUTOCONF_GLIBC_PREREQ(1, 90)
+#  define HAVE_SETFD 1
+#endif
diff --git a/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_SETRLIMIT.h b/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_SETRLIMIT.h
new file mode 100644
index 0000000..1e62e02
--- /dev/null
+++ b/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_SETRLIMIT.h
@@ -0,0 +1,18 @@
+// HAVE_SETRLIMIT : BUILD2_AUTOCONF_LIBC_VERSION
+
+#ifndef BUILD2_AUTOCONF_LIBC_VERSION
+#  error BUILD2_AUTOCONF_LIBC_VERSION appears to be conditionally included
+#endif
+
+#undef HAVE_SETRLIMIT
+
+/* Since 4.2BSD (Linux, OpenBSD, FreeBSD, NetBSD, Mac OS X)
+ * glibc 1.90
+ */
+#if defined(__FreeBSD__)            || \
+    defined(__OpenBSD__)            || \
+    defined(__NetBSD__)             || \
+    defined(BUILD2_AUTOCONF_MACOS)  || \
+    BUILD2_AUTOCONF_GLIBC_PREREQ(1, 90)
+#  define HAVE_SETRLIMIT 1
+#endif
diff --git a/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_UNSETENV.h b/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_UNSETENV.h
new file mode 100644
index 0000000..c01ecbf
--- /dev/null
+++ b/libbuild2-autoconf/libbuild2/autoconf/checks/HAVE_UNSETENV.h
@@ -0,0 +1,18 @@
+// HAVE_UNSETENV : BUILD2_AUTOCONF_LIBC_VERSION
+
+#ifndef BUILD2_AUTOCONF_LIBC_VERSION
+#  error BUILD2_AUTOCONF_LIBC_VERSION appears to be conditionally included
+#endif
+
+#undef HAVE_UNSETENV
+
+/* Since Version 7 AT&T UNIX, 4.3BSD-Tahoe (OpenBSD, FreeBSD, NetBSD, Mac OS X),
+ * glibc 1.90
+ */
+#if defined(__FreeBSD__)            || \
+    defined(__OpenBSD__)            || \
+    defined(__NetBSD__)             || \
+    defined(BUILD2_AUTOCONF_MACOS)  || \
+    BUILD2_AUTOCONF_GLIBC_PREREQ(1, 90)
+#  define HAVE_UNSETENV 1
+#endif