diff --git a/ChangeLog b/ChangeLog
index 0351ec1..f519f41 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -92,6 +92,17 @@ matching to find the minimum value for this limit.
 memory allocation functions were used instead of whatever was used when the 
 pattern was compiled.
 
+17. Changes to the pcre2test "memory" modifier on a subject line. These apply
+only to pcre2_match():
+
+  (a) Warn if null_context is set on both pattern and subject, because the
+      memory details cannot then be shown.
+      
+  (b) Remember (up to a certain number of) memory allocations and their
+      lengths, and list only the lengths, so as to be system-independent.
+      (In practice, the new interpreter never has more than 2 blocks allocated 
+      simultaneously.) 
+
 
 Version 10.23 14-February-2017
 ------------------------------
diff --git a/doc/pcre2test.1 b/doc/pcre2test.1
index 4d5dc73..ff6e53e 100644
--- a/doc/pcre2test.1
+++ b/doc/pcre2test.1
@@ -1,4 +1,4 @@
-.TH PCRE2TEST 1 "24 March 2017" "PCRE 10.30"
+.TH PCRE2TEST 1 "25 March 2017" "PCRE 10.30"
 .SH NAME
 pcre2test - a program for testing Perl-compatible regular expressions.
 .SH SYNOPSIS
@@ -1333,11 +1333,15 @@ is added to the non-match message.
 .SS "Showing memory usage"
 .rs
 .sp
-The \fBmemory\fP modifier causes \fBpcre2test\fP to log all heap memory
-allocation and freeing calls that occur during a call to \fBpcre2_match()\fP.
-These occur only when a match requires a bigger vector than the default for
-remembering backtracking points. In many cases there will be none. No heap
-memory is allocated during matching with \fBpcre2_dfa_match\fP or with JIT.
+The \fBmemory\fP modifier causes \fBpcre2test\fP to log the sizes of all heap
+memory allocation and freeing calls that occur during a call to
+\fBpcre2_match()\fP. These occur only when a match requires a bigger vector
+than the default for remembering backtracking points. In many cases there will
+be no heap memory used and therefore no additional output. No heap memory is
+allocated during matching with \fBpcre2_dfa_match\fP or with JIT, so in those
+cases the \fBmemory\fP modifier never has any effect. For this modifier to
+work, the \fBnull_context\fP modifier must not be set on both the pattern and
+the subject, though it can be set on one or the other.
 .
 .
 .SS "Setting a starting offset"
@@ -1771,6 +1775,6 @@ Cambridge, England.
 .rs
 .sp
 .nf
-Last updated: 24 March 2017
+Last updated: 25 March 2017
 Copyright (c) 1997-2017 University of Cambridge.
 .fi
diff --git a/src/pcre2test.c b/src/pcre2test.c
index cebd323..e758523 100644
--- a/src/pcre2test.c
+++ b/src/pcre2test.c
@@ -78,6 +78,10 @@ from www.cbttape.org. */
 #include <unistd.h>
 #endif
 
+/* Debugging code enabler */
+
+// #define DEBUG_SHOW_MALLOC_ADDRESSES
+
 /* Both libreadline and libedit are optionally supported. The user-supplied
 original patch uses readline/readline.h for libedit, but in at least one system
 it is installed as editline/readline.h, so the configuration code now looks for
@@ -188,6 +192,7 @@ void vms_setsymbol( char *, char *, int );
 #define JUNK_OFFSET 0xdeadbeef  /* For initializing ovector */
 #define LOCALESIZE 32           /* Size of locale name */
 #define LOOPREPEAT 500000       /* Default loop count for timing */
+#define MALLOCLISTSIZE 20       /* For remembering mallocs */
 #define PATSTACKSIZE 20         /* Pattern stack for save/restore testing */
 #define REPLACE_MODSIZE 100     /* Field for reading 8-bit replacement */
 #define VERSION_SIZE 64         /* Size of buffer for the version strings */
@@ -839,6 +844,10 @@ static datctl dat_datctl;
 static void *patstack[PATSTACKSIZE];
 static int patstacknext = 0;
 
+static void *malloclist[MALLOCLISTSIZE];
+static PCRE2_SIZE malloclistlength[MALLOCLISTSIZE];
+static uint32_t malloclistptr = 0;
+
 #ifdef SUPPORT_PCRE2_8
 static regex_t preg = { NULL, NULL, 0, 0, 0 };
 #endif
@@ -2435,12 +2444,32 @@ return sys_errlist[n];
 
 /* Alternative memory functions, to test functionality. */
 
-static void *my_malloc(size_t size, void *data)
+static void *my_malloc(PCRE2_SIZE size, void *data)
 {
 void *block = malloc(size);
 (void)data;
 if (show_memory)
-  fprintf(outfile, "malloc       %3d %p\n", (int)size, block);
+  {
+  if (block == NULL)
+    {
+    fprintf(outfile, "** malloc() failed for %zd\n", size);
+    }
+  else
+    {       
+    fprintf(outfile, "malloc  %5zd", size);
+#ifdef DEBUG_SHOW_MALLOC_ADDRESSES
+    fprintf(outfile, " %p", block);   /* Not portable */
+#endif     
+    if (malloclistptr < MALLOCLISTSIZE)
+      {
+      malloclist[malloclistptr] = block;
+      malloclistlength[malloclistptr++] = size;
+      }    
+    else 
+      fprintf(outfile, " (not remembered)");
+    fprintf(outfile, "\n"); 
+    }   
+  } 
 return block;
 }
 
@@ -2448,7 +2477,32 @@ static void my_free(void *block, void *data)
 {
 (void)data;
 if (show_memory)
-  fprintf(outfile, "free             %p\n", block);
+  {
+  uint32_t i, j; 
+  BOOL found = FALSE;
+  
+  fprintf(outfile, "free");
+  for (i = 0; i < malloclistptr; i++)
+    {
+    if (block == malloclist[i])
+      {
+      fprintf(outfile, "    %5zd", malloclistlength[i]);
+      malloclistptr--; 
+      for (j = i; j < malloclistptr; j++)
+        {
+        malloclist[j] = malloclist[j+1];
+        malloclistlength[j] = malloclistlength[j+1];
+        }
+      found = TRUE;   
+      break;       
+      }    
+    }
+  if (!found) fprintf(outfile, " unremembered block");
+#ifdef DEBUG_SHOW_MALLOC_ADDRESSES   
+  fprintf(outfile, " %p", block);  /* Not portable */
+#endif   
+  fprintf(outfile, "\n");
+  } 
 free(block);
 }
 
@@ -6145,7 +6199,7 @@ if (pat_patctl.replacement[0] != 0 &&
   fprintf(outfile, "** Replacement text is not supported with null_context.\n");
   return PR_OK;
   }
-
+  
 /* We now have the subject in dbuffer, with len containing the byte length, and
 ulen containing the code unit length, with a copy in arg_ulen for use in match
 function arguments (this gets changed to PCRE2_ZERO_TERMINATED when the
@@ -6288,10 +6342,16 @@ NULL context. */
 use_dat_context = ((dat_datctl.control & CTL_NULLCONTEXT) != 0)?
   NULL : PTR(dat_context);
 
-/* Enable display of malloc/free if wanted. */
+/* Enable display of malloc/free if wanted. We can do this only if either the 
+pattern or the subject is processed with a context. */
 
 show_memory = (dat_datctl.control & CTL_MEMORY) != 0;
 
+if (show_memory && 
+    (pat_patctl.control & dat_datctl.control & CTL_NULLCONTEXT) != 0)
+  fprintf(outfile, "** \\=memory requires either a pattern or a subject "
+    "context: ignored\n");    
+
 /* Create and assign a JIT stack if requested. */
 
 if (dat_datctl.jitstack != 0)