Index: polyml/libpolyml/foreign.cpp
===================================================================
--- polyml/libpolyml/foreign.cpp	(revision 1953)
+++ polyml/libpolyml/foreign.cpp	(revision 1954)
@@ -4,7 +4,7 @@
 
     Copyright (c) 2000-7
         Cambridge University Technical Services Limited
-    Further development Copyright David C.J. Matthews 2008-2011.
+    Further development Copyright David C.J. Matthews 2008-2014.
 
     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Lesser General Public
@@ -251,6 +251,10 @@
 
 static Volatile *vols;
 static PLock volLock; // Mutex to protect vols.
+// TODO: There is a theoretical risk of deadlock if any ML allocation is made while this
+// lock is held.  An allocation can result in a GC which requires all threads to release
+// ML memory but another thread could block waiting for the mutex.
+// N.B. raising an exception involves an allocation.
 
 #define FIRST_VOL 0
 
@@ -268,24 +272,8 @@
 static unsigned callBackEntries = 0;
 static PLock callbackTableLock; // Mutex to protect table.
 
-
 /**********************************************************************
  *
- *  Malloc / Free Wrappers
- *   
- **********************************************************************/
-
-static POLYUNSIGNED malloc_count = 0;
-#if 0
-#define Vmalloc(where,size) {where = malloc(size); printf("malloc: %p,%d\n",where,size); fflush(stdout); malloc_count++;}
-#else
-#define Vmalloc(where,size) {where = malloc(size); malloc_count++;}
-#endif
-#define Vfree(p) { free(p);  malloc_count--;}
-
-
-/**********************************************************************
- *
  *  Volatile Allocation
  *   
  **********************************************************************/
@@ -349,8 +337,12 @@
     PLocker plocker(&volLock);
     Handle res = vol_alloc(taskData);
     trace(("size= %" POLYUFMT "\n",size));
-    Vmalloc( C_POINTER(UNVOLHANDLE(res)), size );
+    void *p = malloc(size);
+    if (p == 0)
+        RAISE_EXN("Insufficient memory");
+    C_POINTER(UNVOLHANDLE(res)) = p;
     OWN_C_SPACE(UNVOLHANDLE(res)) = true;
+
     return res;
 }
 
@@ -685,7 +677,7 @@
             {
                 // Can now free this.            
                 trace(("Freeing malloc space of <%" POLYUFMT ">\n",from));
-                Vfree(vols[from].C_pointer);
+                free(vols[from].C_pointer);
                 vols[from].C_pointer = 0;
                 vols[from].Own_C_space = false;
             }
@@ -702,7 +694,6 @@
         }
     }
     next_vol = to;
-    info(("unfreed mallocs=<%" POLYUFMT "> next_vol=<%" POLYUFMT ">\n", malloc_count, next_vol));
     
     /* Callback table.  Added DCJM 12/4/04.  We always process these as strong references.
     For the time being at any rate we treat these as permanent entries so that once a
@@ -910,8 +901,9 @@
         RAISE_EXN("libffi error: ffi_prep_cif failed");
 
     // malloc memory for the result
-    void *result;
-    Vmalloc(result, result_type->size);
+    void *result = malloc(result_type->size);
+    if (result == 0)
+        RAISE_EXN("Insufficient memory to allocate space for result");
 
     processes->ThreadReleaseMLMemory(taskData);
     ffi_call(&cif, sym, result, arg_values);
@@ -1580,6 +1572,9 @@
 
     unsigned num_args = length_list(argTypeList->Word());
     ffi_type **arg_types = (ffi_type**)malloc(num_args * sizeof(ffi_type*));
+    if (arg_types == 0)
+        RAISE_EXN("Insufficient memory to allocate space for arguments");
+
     PolyWord p = argTypeList->Word();
     for (POLYUNSIGNED i=0; i<num_args; i++,p=Tail(p))
         arg_types[i] = ctypeToFfiType(taskData, Head(p));
@@ -1587,6 +1582,9 @@
 
     // The cif needs to be on the heap so that it is available in the callback.
     ffi_cif *cif = (ffi_cif *)malloc(sizeof(ffi_cif));
+    if (cif == 0)
+        RAISE_EXN("Insufficient memory to allocate space for cif");
+
     if (ffi_prep_cif(cif, abi, num_args, result_type, arg_types) != FFI_OK)
         RAISE_EXN("libffi error: ffi_prep_cif failed");