* configure.ac: Check whether sys/sysinfo.h provides

Linux 'sysinfo' function and 'struct sysinfo' type.
* src/alloc.c (Fmemory_info): New function.
* lisp/files.el (warn-maybe-out-of-memory): New function.
(find-file-noselect): Use it.

ChangeLog

@@ -1,3 +1,8 @@
+2014-07-10  Dmitry Antipov  <dmantipov@yandex.ru>
+
+	* configure.ac: Check whether sys/sysinfo.h provides
+	Linux 'sysinfo' function and 'struct sysinfo' type.
+
 2014-06-28  Glenn Morris  <rgm@gnu.org>
 
 	* configure.ac (lwlib_deps_frag, oldxmenu_deps_frag): New output files.

configure.ac

@@ -1510,6 +1510,7 @@ fi
 dnl checks for header files
 AC_CHECK_HEADERS_ONCE(
   sys/systeminfo.h
+  sys/sysinfo.h
   coff.h pty.h
   sys/resource.h
   sys/utsname.h pwd.h utmp.h util.h)
@@ -1525,6 +1526,21 @@ if test $emacs_cv_personality_linux32 = yes; then
             [Define to 1 if personality LINUX32 can be set.])
 fi
 
+if test "$ac_cv_header_sys_sysinfo_h" = yes; then
+  AC_MSG_CHECKING([if Linux sysinfo may be used])
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <sys/sysinfo.h>]],
+                                     [[struct sysinfo si; sysinfo (&si)]])],
+    emacs_cv_linux_sysinfo=yes, emacs_cv_linux_sysinfo=no)
+  AC_MSG_RESULT($emacs_cv_linux_sysinfo)
+  if test $emacs_cv_linux_sysinfo = yes; then
+    AC_DEFINE([HAVE_LINUX_SYSINFO], 1, [Define to 1 if you have Linux sysinfo function.])
+    AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <sys/sysinfo.h>]],
+                                       [[struct sysinfo si; return si.mem_unit]])],
+      AC_DEFINE(LINUX_SYSINFO_UNIT, 1,
+                [Define to 1 if Linux sysinfo sizes are in multiples of mem_unit bytes.]))
+  fi
+fi  
+
 dnl On Solaris 8 there's a compilation warning for term.h because
 dnl it doesn't define `bool'.
 AC_CHECK_HEADERS(term.h, , , -)

lisp/ChangeLog

@@ -1,3 +1,8 @@
+2014-07-10  Dmitry Antipov  <dmantipov@yandex.ru>
+
+	* files.el (warn-maybe-out-of-memory): New function.
+	(find-file-noselect): Use it.
+
 2014-07-09  Sam Steingold  <sds@gnu.org>
 
 	* progmodes/cperl-mode.el (cperl-block-p): Treat the perl keyword

lisp/files.el

@@ -1796,6 +1796,22 @@ OP-TYPE specifies the file operation being performed (for message to user)."
 				    (file-size-human-readable size) op-type))))
     (error "Aborted")))
 
+(defun warn-maybe-out-of-memory (size)
+  "Warn if an attempt to open file of SIZE bytes may run out of memory."
+  (let ((meminfo (memory-info)))
+    (when (consp meminfo)
+      (let ((total-free-memory (+ (nth 1 meminfo) (nth 3 meminfo))))
+	(when (and (not (zerop size))
+		   (> (/ size 1024) total-free-memory))
+	  (warn
+	   "You are trying to open file which size (%s)
+exceeds an amount of available free memory (%s).  If that
+fails, try to open it with `find-file-literally' (but note
+that some characters may be displayed incorrectly)."
+	   (file-size-human-readable size)
+	   (file-size-human-readable
+	    (* (float total-free-memory) 1024))))))))
+
 (defun find-file-noselect (filename &optional nowarn rawfile wildcards)
   "Read file FILENAME into a buffer and return the buffer.
 If a buffer exists visiting FILENAME, return that one, but
@@ -1848,7 +1864,8 @@ the various files."
 		  (setq buf other))))
 	;; Check to see if the file looks uncommonly large.
 	(when (not (or buf nowarn))
-	  (abort-if-file-too-large (nth 7 attributes) "open" filename))
+	  (abort-if-file-too-large (nth 7 attributes) "open" filename)
+	  (warn-maybe-out-of-memory (nth 7 attributes)))
 	(if buf
 	    ;; We are using an existing buffer.
 	    (let (nonexistent)

src/ChangeLog

@@ -9,6 +9,8 @@
 	(decode_coding_big5, decode_coding_charset, decode_coding)
 	(encode_coding): Adjust users.
 
+	* alloc.c (Fmemory_info): New function.
+
 2014-07-09  Paul Eggert  <eggert@cs.ucla.edu>
 
 	* syntax.c (back_comment): Use more-natural location for label.

src/alloc.c

@@ -49,6 +49,10 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <verify.h>
 #include <execinfo.h>           /* For backtrace.  */
 
+#ifdef HAVE_LINUX_SYSINFO
+#include <sys/sysinfo.h>
+#endif
+
 #if (defined ENABLE_CHECKING			\
      && defined HAVE_VALGRIND_VALGRIND_H	\
      && !defined USE_VALGRIND)
@@ -6865,7 +6869,33 @@ gc_sweep (void)
   check_string_bytes (!noninteractive);
 }
 
-
+DEFUN ("memory-info", Fmemory_info, Smemory_info, 0, 0, 0,
+       doc: /* Return a list of (TOTAL-RAM FREE-RAM TOTAL-SWAP FREE-SWAP).
+All values are in Kbytes.  If there is no swap space, last two
+values are zero.  If the system is not supported, return nil.  */)
+  (void)
+{
+#ifdef HAVE_LINUX_SYSINFO
+  struct sysinfo si;
+  uintmax_t units;
+
+  if (sysinfo (&si))
+    emacs_abort ();
+#ifdef LINUX_SYSINFO_UNIT
+  units = si.mem_unit;
+#else
+  units = 1;
+#endif  
+  return list4i ((uintmax_t) si.totalram * units / 1024,
+		 (uintmax_t) si.freeram * units / 1024,
+		 (uintmax_t) si.totalswap * units / 1024,
+		 (uintmax_t) si.freeswap * units / 1024);
+#else /* not HAVE_LINUX_SYSINFO */
+  /* FIXME: add more systems.  */
+  return Qnil;
+#endif /* HAVE_LINUX_SYSINFO */
+}
+
 /* Debugging aids.  */
 
 DEFUN ("memory-limit", Fmemory_limit, Smemory_limit, 0, 0, 0,
@@ -7204,6 +7234,7 @@ The time is in seconds as a floating point value.  */);
   defsubr (&Spurecopy);
   defsubr (&Sgarbage_collect);
   defsubr (&Smemory_limit);
+  defsubr (&Smemory_info);
   defsubr (&Smemory_use_counts);
   defsubr (&Ssuspicious_object);