Resync config/ from GCC.

1 files changed, 97 insertions, 0 deletions

diff --git a/config/mmap.m4 b/config/mmap.m4
new file mode 100644
index 0000000..fba0d9d
--- /dev/null
+++ b/config/mmap.m4
@@ -0,0 +1,97 @@
+dnl ----------------------------------------------------------------------
+dnl This whole bit snagged from gcc
+
+dnl
+dnl mmap(2) blacklisting.  Some platforms provide the mmap library routine
+dnl but don't support all of the features we need from it.
+dnl
+AC_DEFUN([GCC_AC_FUNC_MMAP_BLACKLIST],
+[
+AC_CHECK_HEADER([sys/mman.h],
+		[gcc_header_sys_mman_h=yes], [gcc_header_sys_mman_h=no])
+AC_CHECK_FUNC([mmap], [gcc_func_mmap=yes], [gcc_func_mmap=no])
+if test "$gcc_header_sys_mman_h" != yes \
+ || test "$gcc_func_mmap" != yes; then
+   gcc_cv_func_mmap_file=no
+   gcc_cv_func_mmap_dev_zero=no
+   gcc_cv_func_mmap_anon=no
+else
+   AC_CACHE_CHECK([whether read-only mmap of a plain file works], 
+  gcc_cv_func_mmap_file,
+  [# Add a system to this blacklist if 
+   # mmap(0, stat_size, PROT_READ, MAP_PRIVATE, fd, 0) doesn't return a
+   # memory area containing the same data that you'd get if you applied
+   # read() to the same fd.  The only system known to have a problem here
+   # is VMS, where text files have record structure.
+   case "$host_os" in
+     *vms* | ultrix*)
+        gcc_cv_func_mmap_file=no ;;
+     *)
+        gcc_cv_func_mmap_file=yes;;
+   esac])
+   AC_CACHE_CHECK([whether mmap from /dev/zero works],
+  gcc_cv_func_mmap_dev_zero,
+  [# Add a system to this blacklist if it has mmap() but /dev/zero
+   # does not exist, or if mmapping /dev/zero does not give anonymous
+   # zeroed pages with both the following properties:
+   # 1. If you map N consecutive pages in with one call, and then
+   #    unmap any subset of those pages, the pages that were not
+   #    explicitly unmapped remain accessible.
+   # 2. If you map two adjacent blocks of memory and then unmap them
+   #    both at once, they must both go away.
+   # Systems known to be in this category are Windows (all variants),
+   # VMS, and Darwin.
+   case "$host_os" in
+     *vms* | cygwin* | pe | mingw* | darwin* | ultrix* | hpux10* | hpux11.00)
+        gcc_cv_func_mmap_dev_zero=no ;;
+     *)
+        gcc_cv_func_mmap_dev_zero=yes;;
+   esac])
+
+   # Unlike /dev/zero, the MAP_ANON(YMOUS) defines can be probed for.
+   AC_CACHE_CHECK([for MAP_ANON(YMOUS)], gcc_cv_decl_map_anon,
+    [AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
+[#include <sys/types.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#ifndef MAP_ANONYMOUS
+#define MAP_ANONYMOUS MAP_ANON
+#endif
+],
+[int n = MAP_ANONYMOUS;])],
+    gcc_cv_decl_map_anon=yes,
+    gcc_cv_decl_map_anon=no)])
+
+   if test $gcc_cv_decl_map_anon = no; then
+     gcc_cv_func_mmap_anon=no
+   else
+     AC_CACHE_CHECK([whether mmap with MAP_ANON(YMOUS) works],
+     gcc_cv_func_mmap_anon,
+  [# Add a system to this blacklist if it has mmap() and MAP_ANON or
+   # MAP_ANONYMOUS, but using mmap(..., MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
+   # doesn't give anonymous zeroed pages with the same properties listed
+   # above for use of /dev/zero.
+   # Systems known to be in this category are Windows, VMS, and SCO Unix.
+   case "$host_os" in
+     *vms* | cygwin* | pe | mingw* | sco* | udk* )
+        gcc_cv_func_mmap_anon=no ;;
+     *)
+        gcc_cv_func_mmap_anon=yes;;
+   esac])
+   fi
+fi
+
+if test $gcc_cv_func_mmap_file = yes; then
+  AC_DEFINE(HAVE_MMAP_FILE, 1,
+	    [Define if read-only mmap of a plain file works.])
+fi
+if test $gcc_cv_func_mmap_dev_zero = yes; then
+  AC_DEFINE(HAVE_MMAP_DEV_ZERO, 1,
+	    [Define if mmap of /dev/zero works.])
+fi
+if test $gcc_cv_func_mmap_anon = yes; then
+  AC_DEFINE(HAVE_MMAP_ANON, 1,
+	    [Define if mmap with MAP_ANON(YMOUS) works.])
+fi
+])