Improve AC_FUNC_MMAP comments

* lib/autoconf/functions.m4 (AC_FUNC_MMAP): Add comment.

diff --git a/lib/autoconf/functions.m4 b/lib/autoconf/functions.m4
index 3d6e4aca8db0269ae6a1f48a5e53713003825363..54d04cc382432ecbba0c95d1b64b62b55fb43cf0 100644 (file)
--- a/lib/autoconf/functions.m4
+++ b/lib/autoconf/functions.m4
@@ -1311,6 +1311,8 @@ AC_CACHE_CHECK([for working mmap], [ac_cv_func_mmap_fixed_mapped],
 #include <sys/mman.h>
 
 #ifndef getpagesize
+/* Prefer sysconf to the legacy getpagesize function, as getpagesize has
+   been removed from POSIX and is limited to page sizes that fit in 'int'.  */
 # ifdef _SC_PAGESIZE
 #  define getpagesize() sysconf (_SC_PAGESIZE)
 # elif defined _SC_PAGE_SIZE