diff --git a/libbuild2-autoconf/libbuild2/autoconf/checks/BUILD2_AUTOCONF_LIBC_VERSION.h b/libbuild2-autoconf/libbuild2/autoconf/checks/BUILD2_AUTOCONF_LIBC_VERSION.h
index dad33e0..a66074e 100644
--- a/libbuild2-autoconf/libbuild2/autoconf/checks/BUILD2_AUTOCONF_LIBC_VERSION.h
+++ b/libbuild2-autoconf/libbuild2/autoconf/checks/BUILD2_AUTOCONF_LIBC_VERSION.h
@@ -32,11 +32,16 @@
  * #if defined(__OpenBSD__)
  * #if defined(__NetBSD__)
  *
- * Except for MacOS, which we detect using our own macro (for the sake of
- * simplicity):
+ * Except for MacOS specifically, which we detect using our own macro (for
+ * the sake of simplicity):
  *
  * #if defined(BUILD2_AUTOCONF_MACOS)
  *
+ * If, however, you want to cover the entire Apple operation systems family,
+ * then use:
+ *
+ * #if defined(__APPLE__)
+ *
  * Macros for detecting platforms and their versions:
  *
  * __GLIBC__: The glibc major version number.
diff --git a/libbuild2-autoconf/libbuild2/autoconf/checks/socklen_t.h b/libbuild2-autoconf/libbuild2/autoconf/checks/socklen_t.h
index cef454d..c51a05e 100644
--- a/libbuild2-autoconf/libbuild2/autoconf/checks/socklen_t.h
+++ b/libbuild2-autoconf/libbuild2/autoconf/checks/socklen_t.h
@@ -1,10 +1,9 @@
-// socklen_t : BUILD2_AUTOCONF_LIBC_VERSION
+// socklen_t!
 
-#ifndef BUILD2_AUTOCONF_LIBC_VERSION
-#  error BUILD2_AUTOCONF_LIBC_VERSION appears to be conditionally included
-#endif
-
-#undef socklen_t
+/* If socklen_t is already defined, assume it's correct and use it as-is (see
+ * ssize_t for details).
+ */
+#ifndef socklen_t
 
 /* Since 4.xBSD, SunOS
  * The Single UNIX Specification, Version 2
@@ -13,19 +12,20 @@
  *   To forestall portability problems, it is recommended that
  *   applications should not use values larger than 232 - 1.
  */
-#if defined(__linux__)                  || \
-    defined(__FreeBSD__)                || \
-    defined(__OpenBSD__)                || \
-    defined(__NetBSD__)                 || \
-    defined(BUILD2_AUTOCONF_MACOS)      || \
-    (defined(__sun) && defined(__SVR4)) || \
-    defined(__CYGWIN__)
-#   include <sys/socket.h>
-    /* If available, we do nothing. */
-#elif defined(_WIN32)
-#   include <ws2tcpip.h>
-    /* If available, we do nothing. */
-#else
-    /* Else define it to unsigned int (suggested fallback by libevent). */
-#   define socklen_t unsigned int
+#  if defined(__linux__)                  || \
+      defined(__FreeBSD__)                || \
+      defined(__OpenBSD__)                || \
+      defined(__NetBSD__)                 || \
+      defined(__APPLE__)                  || \
+      (defined(__sun) && defined(__SVR4)) || \
+      defined(__CYGWIN__)
+#     include <sys/socket.h>
+      /* If available, we do nothing. */
+#  elif defined(_WIN32)
+#     include <ws2tcpip.h>
+      /* If available, we do nothing. */
+#  else
+      /* Else define it to unsigned int (suggested fallback by libevent). */
+#     define socklen_t unsigned int
+#  endif
 #endif
diff --git a/libbuild2-autoconf/libbuild2/autoconf/checks/ssize_t.h b/libbuild2-autoconf/libbuild2/autoconf/checks/ssize_t.h
index 2d18f6d..eb57536 100644
--- a/libbuild2-autoconf/libbuild2/autoconf/checks/ssize_t.h
+++ b/libbuild2-autoconf/libbuild2/autoconf/checks/ssize_t.h
@@ -1,28 +1,30 @@
-// ssize_t : BUILD2_AUTOCONF_LIBC_VERSION
+// ssize_t!
 
-#ifndef BUILD2_AUTOCONF_LIBC_VERSION
-#  error BUILD2_AUTOCONF_LIBC_VERSION appears to be conditionally included
-#endif
-
-#undef ssize_t
-
-/* POSIX and MinGW (which also has <sys/types.h> that defines ssize_t).
+/* If ssize_t is already defined, assume it's correct and use it as-is.
+ *
+ * Note that we may not be able to redefine it because while we can undef the
+ * macro, there is no guarantee we will be able to re-include the header (due
+ * to include guards).
  */
-#if defined(__linux__)                  || \
-    defined(__FreeBSD__)                || \
-    defined(__OpenBSD__)                || \
-    defined(__NetBSD__)                 || \
-    defined(BUILD2_AUTOCONF_MACOS)      || \
-    defined(__MINGW32__)                || \
-    (defined(__sun) && defined(__SVR4)) || \
-    defined(__CYGWIN__)
-#  include <sys/types.h>
-   /* If available, we do nothing. */
-#elif defined(_WIN32)
-#  include <basetsd.h>
-   /* Use define instead of typedef to avoid conflicts. */
-#  define ssize_t SSIZE_T
-#else
-   /* Else define it to int (suggested fallback by libevent). */
-#  define ssize_t int
+#ifndef ssize_t
+  /* POSIX and MinGW (which also has <sys/types.h> that defines ssize_t).
+   */
+#  if defined(__linux__)                  || \
+      defined(__FreeBSD__)                || \
+      defined(__OpenBSD__)                || \
+      defined(__NetBSD__)                 || \
+      defined(__APPLE__)                  || \
+      defined(__MINGW32__)                || \
+      (defined(__sun) && defined(__SVR4)) || \
+      defined(__CYGWIN__)
+#    include <sys/types.h>
+     /* If available, we do nothing. */
+#  elif defined(_WIN32)
+#    include <basetsd.h>
+     /* Use define instead of typedef to avoid conflicts. */
+#    define ssize_t SSIZE_T
+#  else
+     /* Else define it to int (suggested fallback by libevent). */
+#    define ssize_t int
+#  endif
 #endif