--- erts/emulator/beam/erl_trace.c@@/OTP_R12B-3	2008-04-07 15:58:12.000000000 +0200
+++ erts/emulator/beam/erl_trace.c@@/main/release/r12b_patch/r12b_otp_7399/1	2008-06-12 11:17:55.000000000 +0200
@@ -32,6 +32,8 @@
 #include "dist.h"
 #include "beam_bp.h"
 #include "error.h"
+#include "erl_binary.h"
+#include "erl_bits.h"
 
 #if 0
 #define DEBUG_PRINTOUTS
@@ -1445,7 +1447,9 @@
 #ifdef ERTS_SMP
     Eterm tracee;
 #endif
-    
+    Eterm transformed_args[MAX_ARG];
+    ErlSubBin sub_bin_heap;
+
     ASSERT(tracer_pid);
     if (*tracer_pid == am_true) {
 	/* Breakpoint trace enabled without specifying tracer =>
@@ -1488,6 +1492,42 @@
 #endif
     }
 
+    /*
+     * Because of the delayed sub-binary creation optimization introduced in
+     * R12B, (at most) one of arguments can be a match context instead of
+     * a binary. Since we don't want to handle match contexts in utility functions
+     * such as size_object() and copy_struct(), we must make sure that we
+     * temporarily convert any match contexts to sub binaries.
+     */
+    arity = mfa[2];
+#ifdef DEBUG
+    sub_bin_heap.thing_word = 0;
+#endif
+    for (i = 0; i < arity; i++) {
+	Eterm arg = args[i];
+	if (is_boxed(arg) && header_is_bin_matchstate(*boxed_val(arg))) {
+	    ErlBinMatchState* ms = (ErlBinMatchState *) boxed_val(arg);
+	    ErlBinMatchBuffer* mb = &ms->mb;
+	    ErlSubBin* sb = &sub_bin_heap;
+	    Uint bit_size;
+
+	    ASSERT(sub_bin_heap.thing_word == 0); /* At most one of match context */
+
+	    bit_size = mb->size - mb->offset;
+	    sb->thing_word = HEADER_SUB_BIN;
+	    sb->size = BYTE_OFFSET(bit_size);
+	    sb->bitsize = BIT_OFFSET(bit_size);
+	    sb->offs = BYTE_OFFSET(mb->offset);
+	    sb->bitoffs = BIT_OFFSET(mb->offset);
+	    sb->is_writable = 0;
+	    sb->orig = mb->orig;
+
+	    arg = make_binary(sb);
+	}
+	transformed_args[i] = arg;
+    }
+    args = transformed_args;
+
     if (is_internal_port(*tracer_pid)) {
 	Eterm local_heap[64+MAX_ARG];
 	hp = local_heap;
@@ -1525,7 +1565,6 @@
 	
 	/* BEGIN this code should be the same for port and pid trace */
 	return_flags = 0;
-	arity = mfa[2];
 	if (match_spec) {
 	    pam_result = erts_match_set_run(p, match_spec, args, arity,
 					    &return_flags);
@@ -1601,7 +1640,7 @@
 	Eterm tpid;
 #endif
 	unsigned size;
-	unsigned sizes[256];
+	unsigned sizes[MAX_ARG];
 	unsigned pam_result_size = 0;
 	int invalid_tracer;
 #ifdef DEBUG
@@ -1652,7 +1691,6 @@
 	
 	/* BEGIN this code should be the same for port and pid trace */
 	return_flags = 0;
-	arity = mfa[2];
 	if (match_spec) {
 	    pam_result = erts_match_set_run(p, match_spec, args, arity,
 					    &return_flags);