(get_lim_data) [MSDOS]: Use alternative methods of estimating available memory.

2 files changed, 26 insertions, 1 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 6d04d426998..89921e7b395 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2008-08-24  Eli Zaretskii  <eliz@gnu.org>
+
+        * vm-limit.c (get_lim_data) [MSDOS]: Use alternative methods of
+        estimating available memory.
+
 2008-08-23  David Reitter <david.reitter@gmail.com> 
         
         * nsterm.m (ns_draw_window_cursor): Don't call
diff --git a/src/vm-limit.c b/src/vm-limit.c
index f80e5c47604..907732c82af 100644
--- a/src/vm-limit.c
+++ b/src/vm-limit.c
@@ -121,9 +121,29 @@ void
 get_lim_data ()
 {
   _go32_dpmi_meminfo info;
+  unsigned long lim1, lim2;
 
   _go32_dpmi_get_free_memory_information (&info);
-  lim_data = info.available_memory;
+  /* DPMI server of Windows NT and its descendants reports in
+     info.available_memory a much lower amount that is really
+     available, which causes bogus "past 95% of memory limit"
+     warnings.  Try to overcome that via circumstantial evidence.  */
+  lim1 = info.available_memory;
+  lim2 = info.available_physical_pages * 4096;
+  /* DPMI Spec: "Fields that are unavailable will hold -1."  */
+  if ((long)lim1 == -1L)
+    lim1 = 0;
+  if ((long)lim2 == -1L)
+    lim2 = 0;
+  /* Surely, the available memory is at least what we have physically
+     available, right?  */
+  if (lim1 > lim2)
+    lim_data = lim1;
+  else
+    lim_data = lim2;
+  /* Don't believe they will give us more that 0.5 GB.   */
+  if (lim_data > 512 * 1024 * 1024)
+    lim_data = 512 * 1024 * 1024;
 }
 #else /* not MSDOS */
 static void