diff --git a/src/core/ddsc/src/dds__stream.h b/src/core/ddsc/src/dds__stream.h
index 347f667..7facf45 100644
--- a/src/core/ddsc/src/dds__stream.h
+++ b/src/core/ddsc/src/dds__stream.h
@@ -60,6 +60,10 @@ void dds_stream_extract_keyhash (dds_istream_t * __restrict is, dds_keyhash_t *
 
 void dds_stream_read_key (dds_istream_t * __restrict is, char * __restrict sample, const struct ddsi_sertopic_default * __restrict topic);
 
+size_t dds_stream_print_key (dds_istream_t * __restrict is, const struct ddsi_sertopic_default * __restrict topic, char * __restrict buf, size_t size);
+
+size_t dds_stream_print_sample (dds_istream_t * __restrict is, const struct ddsi_sertopic_default * __restrict topic, char * __restrict buf, size_t size);
+
 /* For marshalling op code handling */
 
 #define DDS_OP_MASK 0xff000000
diff --git a/src/core/ddsc/src/dds_serdata_builtintopic.c b/src/core/ddsc/src/dds_serdata_builtintopic.c
index 1a97a40..06ae6f4 100644
--- a/src/core/ddsc/src/dds_serdata_builtintopic.c
+++ b/src/core/ddsc/src/dds_serdata_builtintopic.c
@@ -276,6 +276,12 @@ static void serdata_builtin_to_ser_unref (struct ddsi_serdata *serdata_common, c
   (void)serdata_common; (void)ref;
 }
 
+static size_t serdata_builtin_topic_print (const struct ddsi_sertopic *topic, const struct ddsi_serdata *serdata_common, char *buf, size_t size)
+{
+  (void)topic; (void)serdata_common;
+  return (size_t) snprintf (buf, size, "(blob)");
+}
+
 const struct ddsi_serdata_ops ddsi_serdata_ops_builtintopic = {
   .get_size = serdata_builtin_get_size,
   .eqkey = serdata_builtin_eqkey,
@@ -288,5 +294,6 @@ const struct ddsi_serdata_ops ddsi_serdata_ops_builtintopic = {
   .to_ser_ref = serdata_builtin_to_ser_ref,
   .to_ser_unref = serdata_builtin_to_ser_unref,
   .to_topicless = serdata_builtin_to_topicless,
-  .topicless_to_sample = serdata_builtin_topicless_to_sample
+  .topicless_to_sample = serdata_builtin_topicless_to_sample,
+  .print = serdata_builtin_topic_print
 };
diff --git a/src/core/ddsc/src/dds_stream.c b/src/core/ddsc/src/dds_stream.c
index c2264c0..982a532 100644
--- a/src/core/ddsc/src/dds_stream.c
+++ b/src/core/ddsc/src/dds_stream.c
@@ -11,6 +11,7 @@
  */
 #include <assert.h>
 #include <string.h>
+#include <ctype.h>
 
 #include "dds/ddsrt/endian.h"
 #include "dds/ddsrt/md5.h"
@@ -1608,6 +1609,292 @@ void dds_stream_extract_keyhash (dds_istream_t * __restrict is, dds_keyhash_t *
   }
 }
 
+/*******************************************************************************************
+ **
+ **  Pretty-printing
+ **
+ *******************************************************************************************/
+
+/* Returns true if buffer not yet exhausted, false otherwise */
+static bool prtf (char * __restrict *buf, size_t * __restrict bufsize, const char *fmt, ...)
+{
+  va_list ap;
+  if (*bufsize == 0)
+    return false;
+  va_start (ap, fmt);
+  int n = vsnprintf (*buf, *bufsize, fmt, ap);
+  va_end (ap);
+  if (n < 0)
+  {
+    **buf = 0;
+    return false;
+  }
+  else if ((size_t) n <= *bufsize)
+  {
+    *buf += (size_t) n;
+    *bufsize -= (size_t) n;
+    return (*bufsize > 0);
+  }
+  else
+  {
+    *buf += *bufsize;
+    *bufsize = 0;
+    return false;
+  }
+}
+
+static bool prtf_str (char * __restrict *buf, size_t * __restrict bufsize, dds_istream_t * __restrict is)
+{
+  size_t sz = dds_is_get4 (is);
+  bool ret = prtf (buf, bufsize, "\"%s\"", is->m_buffer + is->m_index);
+  is->m_index += (uint32_t) sz;
+  return ret;
+}
+
+static size_t isprint_runlen (const unsigned char *s, size_t n)
+{
+  size_t m;
+  for (m = 0; m < n && s[m] != '"' && isprint (s[m]); m++)
+    ;
+  return m;
+}
+
+static bool prtf_simple (char * __restrict *buf, size_t * __restrict bufsize, dds_istream_t * __restrict is, enum dds_stream_typecode type)
+{
+  switch (type)
+  {
+    case DDS_OP_VAL_1BY: return prtf (buf, bufsize, "%"PRIu8, dds_is_get1 (is));
+    case DDS_OP_VAL_2BY: return prtf (buf, bufsize, "%"PRIu16, dds_is_get2 (is));
+    case DDS_OP_VAL_4BY: return prtf (buf, bufsize, "%"PRIu32, dds_is_get4 (is));
+    case DDS_OP_VAL_8BY: return prtf (buf, bufsize, "%"PRIu64, dds_is_get8 (is));
+    case DDS_OP_VAL_STR: case DDS_OP_VAL_BST: return prtf_str (buf, bufsize, is);
+    case DDS_OP_VAL_ARR: case DDS_OP_VAL_SEQ: case DDS_OP_VAL_UNI: case DDS_OP_VAL_STU:
+      abort ();
+  }
+  return false;
+}
+
+static bool prtf_simple_array (char * __restrict *buf, size_t * __restrict bufsize, dds_istream_t * __restrict is, uint32_t num, enum dds_stream_typecode type)
+{
+  bool cont = prtf (buf, bufsize, "{");
+  switch (type)
+  {
+    case DDS_OP_VAL_1BY: {
+      size_t i = 0, j;
+      while (cont && i < num)
+      {
+        size_t m = isprint_runlen ((unsigned char *) (is->m_buffer + is->m_index), num - i);
+        if (m >= 4)
+        {
+          cont = prtf (buf, bufsize, "%s\"", i != 0 ? "," : "");
+          for (j = 0; cont && j < m; j++)
+            cont = prtf (buf, bufsize, "%c", is->m_buffer[is->m_index + j]);
+          cont = prtf (buf, bufsize, "\"");
+          is->m_index += (uint32_t) m;
+          i += m;
+        }
+        else
+        {
+          if (i != 0)
+            cont = prtf (buf, bufsize, ",");
+          cont = prtf_simple (buf, bufsize, is, type);
+          i++;
+        }
+      }
+      break;
+    }
+    case DDS_OP_VAL_2BY: case DDS_OP_VAL_4BY: case DDS_OP_VAL_8BY:
+    case DDS_OP_VAL_STR: case DDS_OP_VAL_BST:
+      for (size_t i = 0; cont && i < num; i++)
+      {
+        if (i != 0)
+          cont = prtf (buf, bufsize, ",");
+        cont = prtf_simple (buf, bufsize, is, type);
+      }
+      break;
+    default:
+      abort ();
+      break;
+  }
+  return cont;
+}
+
+static bool dds_stream_print_sample1 (char * __restrict *buf, size_t * __restrict bufsize, dds_istream_t * __restrict is, const uint32_t * __restrict ops, bool add_braces);
+
+static const uint32_t *prtf_seq (char * __restrict *buf, size_t *bufsize, dds_istream_t * __restrict is, const uint32_t * __restrict ops, uint32_t insn)
+{
+  const enum dds_stream_typecode subtype = DDS_OP_SUBTYPE (insn);
+  uint32_t num;
+  num = dds_is_get4 (is);
+  if (num == 0)
+  {
+    prtf (buf, bufsize, "{}");
+    return skip_sequence_insns (ops, insn);
+  }
+  switch (subtype)
+  {
+    case DDS_OP_VAL_1BY: case DDS_OP_VAL_2BY: case DDS_OP_VAL_4BY: case DDS_OP_VAL_8BY:
+      prtf_simple_array (buf, bufsize, is, num, subtype);
+      return ops + 2;
+    case DDS_OP_VAL_STR: case DDS_OP_VAL_BST:
+      prtf_simple_array (buf, bufsize, is, num, subtype);
+      return ops + (subtype == DDS_OP_VAL_STR ? 2 : 3);
+    case DDS_OP_VAL_SEQ: case DDS_OP_VAL_ARR: case DDS_OP_VAL_UNI: case DDS_OP_VAL_STU: {
+      const uint32_t jmp = DDS_OP_ADR_JMP (ops[3]);
+      uint32_t const * const jsr_ops = ops + DDS_OP_ADR_JSR (ops[3]);
+      bool cont = prtf (buf, bufsize, "{");
+      for (uint32_t i = 0; cont && i < num; i++)
+      {
+        if (i > 0) prtf (buf, bufsize, ",");
+        cont = dds_stream_print_sample1 (buf, bufsize, is, jsr_ops, subtype == DDS_OP_VAL_STU);
+      }
+      prtf (buf, bufsize, "}");
+      return ops + (jmp ? jmp : 4); /* FIXME: why would jmp be 0? */
+    }
+  }
+  return NULL;
+}
+
+static const uint32_t *prtf_arr (char * __restrict *buf, size_t *bufsize, dds_istream_t * __restrict is, const uint32_t * __restrict ops, uint32_t insn)
+{
+  const enum dds_stream_typecode subtype = DDS_OP_SUBTYPE (insn);
+  const uint32_t num = ops[2];
+  switch (subtype)
+  {
+    case DDS_OP_VAL_1BY: case DDS_OP_VAL_2BY: case DDS_OP_VAL_4BY: case DDS_OP_VAL_8BY:
+      prtf_simple_array (buf, bufsize, is, num, subtype);
+      return ops + 3;
+    case DDS_OP_VAL_STR: case DDS_OP_VAL_BST:
+      prtf_simple_array (buf, bufsize, is, num, subtype);
+      return ops + (subtype == DDS_OP_VAL_STR ? 3 : 5);
+    case DDS_OP_VAL_SEQ: case DDS_OP_VAL_ARR: case DDS_OP_VAL_UNI: case DDS_OP_VAL_STU: {
+      const uint32_t *jsr_ops = ops + DDS_OP_ADR_JSR (ops[3]);
+      const uint32_t jmp = DDS_OP_ADR_JMP (ops[3]);
+      bool cont = prtf (buf, bufsize, "{");
+      for (uint32_t i = 0; cont && i < num; i++)
+      {
+        if (i > 0) prtf (buf, bufsize, ",");
+        cont = dds_stream_print_sample1 (buf, bufsize, is, jsr_ops, subtype == DDS_OP_VAL_STU);
+      }
+      prtf (buf, bufsize, "}");
+      return ops + (jmp ? jmp : 5);
+    }
+  }
+  return NULL;
+}
+
+static const uint32_t *prtf_uni (char * __restrict *buf, size_t *bufsize, dds_istream_t * __restrict is, const uint32_t * __restrict ops, uint32_t insn)
+{
+  const uint32_t disc = read_union_discriminant (is, DDS_OP_SUBTYPE (insn));
+  uint32_t const * const jeq_op = find_union_case (ops, disc);
+  prtf (buf, bufsize, "%"PRIu32":", disc);
+  ops += DDS_OP_ADR_JMP (ops[3]);
+  if (jeq_op)
+  {
+    const enum dds_stream_typecode valtype = DDS_JEQ_TYPE (jeq_op[0]);
+    switch (valtype)
+    {
+      case DDS_OP_VAL_1BY: case DDS_OP_VAL_2BY: case DDS_OP_VAL_4BY: case DDS_OP_VAL_8BY:
+      case DDS_OP_VAL_STR: case DDS_OP_VAL_BST:
+        prtf_simple (buf, bufsize, is, valtype);
+        break;
+      case DDS_OP_VAL_SEQ: case DDS_OP_VAL_ARR: case DDS_OP_VAL_UNI: case DDS_OP_VAL_STU:
+        dds_stream_print_sample1 (buf, bufsize, is, jeq_op + DDS_OP_ADR_JSR (jeq_op[0]), valtype == DDS_OP_VAL_STU);
+        break;
+    }
+  }
+  return ops;
+}
+
+static bool dds_stream_print_sample1 (char * __restrict *buf, size_t * __restrict bufsize, dds_istream_t * __restrict is, const uint32_t * __restrict ops, bool add_braces)
+{
+  uint32_t insn;
+  bool cont = true;
+  bool needs_comma = false;
+  if (add_braces)
+    prtf (buf, bufsize, "{");
+  while (cont && (insn = *ops) != DDS_OP_RTS)
+  {
+    if (needs_comma)
+      prtf (buf, bufsize, ",");
+    needs_comma = true;
+    switch (DDS_OP (insn))
+    {
+      case DDS_OP_ADR: {
+        switch (DDS_OP_TYPE (insn))
+        {
+          case DDS_OP_VAL_1BY: case DDS_OP_VAL_2BY: case DDS_OP_VAL_4BY: case DDS_OP_VAL_8BY:
+          case DDS_OP_VAL_STR:
+            cont = prtf_simple (buf, bufsize, is, DDS_OP_TYPE (insn));
+            ops += 2;
+            break;
+          case DDS_OP_VAL_BST:
+            cont = prtf_simple (buf, bufsize, is, DDS_OP_TYPE (insn));
+            ops += 3;
+            break;
+          case DDS_OP_VAL_SEQ:
+            ops = prtf_seq (buf, bufsize, is, ops, insn);
+            break;
+          case DDS_OP_VAL_ARR:
+            ops = prtf_arr (buf, bufsize, is, ops, insn);
+            break;
+          case DDS_OP_VAL_UNI:
+            ops = prtf_uni (buf, bufsize, is, ops, insn);
+            break;
+          case DDS_OP_VAL_STU:
+            abort ();
+            break;
+        }
+        break;
+      }
+      case DDS_OP_JSR: {
+        cont = dds_stream_print_sample1 (buf, bufsize, is, ops + DDS_OP_JUMP (insn), true);
+        ops++;
+        break;
+      }
+      case DDS_OP_RTS: case DDS_OP_JEQ: {
+        abort ();
+        break;
+      }
+    }
+  }
+  if (add_braces)
+    prtf (buf, bufsize, "}");
+  return cont;
+}
+
+size_t dds_stream_print_sample (dds_istream_t * __restrict is, const struct ddsi_sertopic_default * __restrict topic, char * __restrict buf, size_t bufsize)
+{
+  dds_stream_print_sample1 (&buf, &bufsize, is, topic->type->m_ops, true);
+  return bufsize;
+}
+
+size_t dds_stream_print_key (dds_istream_t * __restrict is, const struct ddsi_sertopic_default * __restrict topic, char * __restrict buf, size_t bufsize)
+{
+  const dds_topic_descriptor_t *desc = topic->type;
+  bool cont = prtf (&buf, &bufsize, ":k:{");
+  for (uint32_t i = 0; cont && i < desc->m_nkeys; i++)
+  {
+    const uint32_t *op = desc->m_ops + desc->m_keys[i].m_index;
+    assert (insn_key_ok_p (*op));
+    switch (DDS_OP_TYPE (*op))
+    {
+      case DDS_OP_VAL_1BY: case DDS_OP_VAL_2BY: case DDS_OP_VAL_4BY: case DDS_OP_VAL_8BY:
+      case DDS_OP_VAL_STR: case DDS_OP_VAL_BST:
+        cont = prtf_simple (&buf, &bufsize, is, DDS_OP_TYPE (*op));
+        break;
+      case DDS_OP_VAL_ARR:
+        cont = prtf_simple_array (&buf, &bufsize, is, op[2], DDS_OP_SUBTYPE (*op));
+        break;
+      case DDS_OP_VAL_SEQ: case DDS_OP_VAL_UNI: case DDS_OP_VAL_STU:
+        abort ();
+        break;
+    }
+  }
+  prtf (&buf, &bufsize, "}");
+  return bufsize;
+}
+
 /*******************************************************************************************
  **
  **  Stuff to make it possible to treat a ddsi_serdata_default as a stream
diff --git a/src/core/ddsi/include/dds/ddsi/ddsi_serdata.h b/src/core/ddsi/include/dds/ddsi/ddsi_serdata.h
index 866910a..4d9b64b 100644
--- a/src/core/ddsi/include/dds/ddsi/ddsi_serdata.h
+++ b/src/core/ddsi/include/dds/ddsi/ddsi_serdata.h
@@ -123,6 +123,15 @@ typedef bool (*ddsi_serdata_topicless_to_sample_t) (const struct ddsi_sertopic *
    computing equijoins across topics much simpler). */
 typedef bool (*ddsi_serdata_eqkey_t) (const struct ddsi_serdata *a, const struct ddsi_serdata *b);
 
+/* Print a serdata into the provided buffer (truncating as necessary)
+   - topic is present for supporting printing of "topicless" samples
+   - buf != NULL, bufsize > 0 on input
+   - buf must always be terminated with a nul character on return
+   - returns the number of characters (excluding the terminating 0) needed to print it
+     in full (or, as an optimization, it may pretend that it has printed it in full,
+     returning bufsize-1) if it had to truncate) */
+typedef size_t (*ddsi_serdata_print_t) (const struct ddsi_sertopic *topic, const struct ddsi_serdata *d, char *buf, size_t size);
+
 struct ddsi_serdata_ops {
   ddsi_serdata_eqkey_t eqkey;
   ddsi_serdata_size_t get_size;
@@ -136,8 +145,11 @@ struct ddsi_serdata_ops {
   ddsi_serdata_to_topicless_t to_topicless;
   ddsi_serdata_topicless_to_sample_t topicless_to_sample;
   ddsi_serdata_free_t free;
+  ddsi_serdata_print_t print;
 };
 
+#define DDSI_SERDATA_HAS_PRINT 1
+
 DDS_EXPORT void ddsi_serdata_init (struct ddsi_serdata *d, const struct ddsi_sertopic *tp, enum ddsi_serdata_kind kind);
 
 DDS_EXPORT inline struct ddsi_serdata *ddsi_serdata_ref (const struct ddsi_serdata *serdata_const) {
@@ -195,6 +207,20 @@ DDS_EXPORT inline bool ddsi_serdata_eqkey (const struct ddsi_serdata *a, const s
   return a->ops->eqkey (a, b);
 }
 
+DDS_EXPORT inline bool ddsi_serdata_print (const struct ddsi_serdata *d, char *buf, size_t size) {
+  return d->ops->print (d->topic, d, buf, size);
+}
+
+DDS_EXPORT inline bool ddsi_serdata_print_topicless (const struct ddsi_sertopic *topic, const struct ddsi_serdata *d, char *buf, size_t size) {
+  if (d->ops->print)
+    return d->ops->print (topic, d, buf, size);
+  else
+  {
+    buf[0] = 0;
+    return 0;
+  }
+}
+
 #if defined (__cplusplus)
 }
 #endif
diff --git a/src/core/ddsi/src/ddsi_serdata.c b/src/core/ddsi/src/ddsi_serdata.c
index 140c049..68caae0 100644
--- a/src/core/ddsi/src/ddsi_serdata.c
+++ b/src/core/ddsi/src/ddsi_serdata.c
@@ -45,3 +45,5 @@ extern inline void ddsi_serdata_to_ser_unref (struct ddsi_serdata *d, const ddsr
 extern inline bool ddsi_serdata_to_sample (const struct ddsi_serdata *d, void *sample, void **bufptr, void *buflim);
 extern inline bool ddsi_serdata_topicless_to_sample (const struct ddsi_sertopic *topic, const struct ddsi_serdata *d, void *sample, void **bufptr, void *buflim);
 extern inline bool ddsi_serdata_eqkey (const struct ddsi_serdata *a, const struct ddsi_serdata *b);
+extern inline bool ddsi_serdata_print (const struct ddsi_serdata *d, char *buf, size_t size);
+extern inline bool ddsi_serdata_print_topicless (const struct ddsi_sertopic *topic, const struct ddsi_serdata *d, char *buf, size_t size);
diff --git a/src/core/ddsi/src/ddsi_serdata_default.c b/src/core/ddsi/src/ddsi_serdata_default.c
index 4aa0699..622b0e2 100644
--- a/src/core/ddsi/src/ddsi_serdata_default.c
+++ b/src/core/ddsi/src/ddsi_serdata_default.c
@@ -629,6 +629,32 @@ static bool serdata_default_topicless_to_sample_cdr_nokey (const struct ddsi_ser
   return true;
 }
 
+static size_t serdata_default_print_cdr (const struct ddsi_sertopic *sertopic_common, const struct ddsi_serdata *serdata_common, char *buf, size_t size)
+{
+  const struct ddsi_serdata_default *d = (const struct ddsi_serdata_default *)serdata_common;
+  const struct ddsi_sertopic_default *tp = (const struct ddsi_sertopic_default *)sertopic_common;
+  dds_istream_t is;
+  dds_istream_from_serdata_default (&is, d);
+  if (d->c.kind == SDK_KEY)
+    return dds_stream_print_key (&is, tp, buf, size);
+  else
+    return dds_stream_print_sample (&is, tp, buf, size);
+}
+
+static size_t serdata_default_print_plist (const struct ddsi_sertopic *sertopic_common, const struct ddsi_serdata *serdata_common, char *buf, size_t size)
+{
+  /* FIXME: should change q_plist.c to print to a string instead of a log, and then drop the
+     logging of QoS in the rest of code, instead relying on this */
+  (void)sertopic_common; (void)serdata_common;
+  return (size_t) snprintf (buf, size, "(plist)");
+}
+
+static size_t serdata_default_print_raw (const struct ddsi_sertopic *sertopic_common, const struct ddsi_serdata *serdata_common, char *buf, size_t size)
+{
+  (void)sertopic_common; (void)serdata_common;
+  return (size_t) snprintf (buf, size, "(blob)");
+}
+
 const struct ddsi_serdata_ops ddsi_serdata_ops_cdr = {
   .get_size = serdata_default_get_size,
   .eqkey = serdata_default_eqkey,
@@ -641,7 +667,8 @@ const struct ddsi_serdata_ops ddsi_serdata_ops_cdr = {
   .to_ser_ref = serdata_default_to_ser_ref,
   .to_ser_unref = serdata_default_to_ser_unref,
   .to_topicless = serdata_default_to_topicless,
-  .topicless_to_sample = serdata_default_topicless_to_sample_cdr
+  .topicless_to_sample = serdata_default_topicless_to_sample_cdr,
+  .print = serdata_default_print_cdr
 };
 
 const struct ddsi_serdata_ops ddsi_serdata_ops_cdr_nokey = {
@@ -656,7 +683,8 @@ const struct ddsi_serdata_ops ddsi_serdata_ops_cdr_nokey = {
   .to_ser_ref = serdata_default_to_ser_ref,
   .to_ser_unref = serdata_default_to_ser_unref,
   .to_topicless = serdata_default_to_topicless,
-  .topicless_to_sample = serdata_default_topicless_to_sample_cdr_nokey
+  .topicless_to_sample = serdata_default_topicless_to_sample_cdr_nokey,
+  .print = serdata_default_print_cdr
 };
 
 const struct ddsi_serdata_ops ddsi_serdata_ops_plist = {
@@ -671,7 +699,8 @@ const struct ddsi_serdata_ops ddsi_serdata_ops_plist = {
   .to_ser_ref = serdata_default_to_ser_ref,
   .to_ser_unref = serdata_default_to_ser_unref,
   .to_topicless = serdata_default_to_topicless,
-  .topicless_to_sample = 0
+  .topicless_to_sample = 0,
+  .print = serdata_default_print_plist
 };
 
 const struct ddsi_serdata_ops ddsi_serdata_ops_rawcdr = {
@@ -686,5 +715,6 @@ const struct ddsi_serdata_ops ddsi_serdata_ops_rawcdr = {
   .to_ser_ref = serdata_default_to_ser_ref,
   .to_ser_unref = serdata_default_to_ser_unref,
   .to_topicless = serdata_default_to_topicless,
-  .topicless_to_sample = 0
+  .topicless_to_sample = 0,
+  .print = serdata_default_print_raw
 };
diff --git a/src/core/ddsi/src/q_config.c b/src/core/ddsi/src/q_config.c
index 6a41dd9..e386ea2 100644
--- a/src/core/ddsi/src/q_config.c
+++ b/src/core/ddsi/src/q_config.c
@@ -1317,14 +1317,17 @@ static enum update_result do_uint32_bitset (struct cfgst *cfgst, uint32_t *cats,
   char *copy = ddsrt_strdup (value), *cursor = copy, *tok;
   while ((tok = ddsrt_strsep (&cursor, ",")) != NULL)
   {
-    const int idx = list_index (names, tok);
+    const int idx = list_index (names, tok[0] == '-' ? tok+1 : tok);
     if (idx < 0)
     {
       const enum update_result ret = cfg_error (cfgst, "'%s' in '%s' undefined", tok, value);
       ddsrt_free (copy);
       return ret;
     }
-    *cats |= codes[idx];
+    if (tok[0] == '-')
+      *cats &= ~codes[idx];
+    else
+      *cats |= codes[idx];
   }
   ddsrt_free (copy);
   return URES_SUCCESS;
@@ -1517,10 +1520,10 @@ GENERIC_ENUM_CTYPE (standards_conformance, enum nn_standards_conformance)
 
 /* "trace" is special: it enables (nearly) everything */
 static const char *tracemask_names[] = {
-  "fatal", "error", "warning", "info", "config", "discovery", "data", "radmin", "timing", "traffic", "topic", "tcp", "plist", "whc", "throttle", "rhc", "trace", NULL
+  "fatal", "error", "warning", "info", "config", "discovery", "data", "radmin", "timing", "traffic", "topic", "tcp", "plist", "whc", "throttle", "rhc", "content", "trace", NULL
 };
 static const uint32_t tracemask_codes[] = {
-  DDS_LC_FATAL, DDS_LC_ERROR, DDS_LC_WARNING, DDS_LC_INFO, DDS_LC_CONFIG, DDS_LC_DISCOVERY, DDS_LC_DATA, DDS_LC_RADMIN, DDS_LC_TIMING, DDS_LC_TRAFFIC, DDS_LC_TOPIC, DDS_LC_TCP, DDS_LC_PLIST, DDS_LC_WHC, DDS_LC_THROTTLE, DDS_LC_RHC, DDS_LC_ALL
+  DDS_LC_FATAL, DDS_LC_ERROR, DDS_LC_WARNING, DDS_LC_INFO, DDS_LC_CONFIG, DDS_LC_DISCOVERY, DDS_LC_DATA, DDS_LC_RADMIN, DDS_LC_TIMING, DDS_LC_TRAFFIC, DDS_LC_TOPIC, DDS_LC_TCP, DDS_LC_PLIST, DDS_LC_WHC, DDS_LC_THROTTLE, DDS_LC_RHC, DDS_LC_CONTENT, DDS_LC_ALL
 };
 
 static enum update_result uf_tracemask (struct cfgst *cfgst, UNUSED_ARG (void *parent), UNUSED_ARG (struct cfgelem const * const cfgelem), UNUSED_ARG (int first), const char *value)
diff --git a/src/core/ddsi/src/q_receive.c b/src/core/ddsi/src/q_receive.c
index a54fd68..a40385c 100644
--- a/src/core/ddsi/src/q_receive.c
+++ b/src/core/ddsi/src/q_receive.c
@@ -1818,6 +1818,21 @@ static struct ddsi_serdata *new_sample_from_data (struct ddsi_tkmap_instance **t
       ddsi_serdata_unref (sample);
       sample = NULL;
     }
+    else if (gv->logconfig.c.mask & DDS_LC_TRACE)
+    {
+      const struct proxy_writer *pwr = sampleinfo->pwr;
+      nn_guid_t guid;
+      char tmp[1024];
+      size_t res = 0;
+      tmp[0] = 0;
+      if (gv->logconfig.c.mask & DDS_LC_CONTENT)
+        res = ddsi_serdata_print (sample, tmp, sizeof (tmp));
+      if (pwr) guid = pwr->e.guid; else memset (&guid, 0, sizeof (guid));
+      GVTRACE ("data(application, vendor %u.%u): "PGUIDFMT" #%"PRId64": ST%x %s/%s:%s%s",
+               sampleinfo->rst->vendor.id[0], sampleinfo->rst->vendor.id[1],
+               PGUID (guid), sampleinfo->seq, statusinfo, topic->name, topic->type_name,
+               tmp, res < sizeof (tmp) ? "" : "(trunc)");
+    }
   }
   return sample;
 }
@@ -1932,9 +1947,8 @@ static int deliver_user_data (const struct nn_rsample_info *sampleinfo, const st
     if ((plist_ret = nn_plist_init_frommsg (&qos, NULL, PP_STATUSINFO | PP_KEYHASH | PP_COHERENT_SET, 0, &src)) < 0)
     {
       if (plist_ret != DDS_RETCODE_UNSUPPORTED)
-        DDS_CWARNING (&gv->logconfig,
-                      "data(application, vendor %u.%u): "PGUIDFMT" #%"PRId64": invalid inline qos\n",
-                      src.vendorid.id[0], src.vendorid.id[1], PGUID (pwr->e.guid), sampleinfo->seq);
+        GVWARNING ("data(application, vendor %u.%u): "PGUIDFMT" #%"PRId64": invalid inline qos\n",
+                   src.vendorid.id[0], src.vendorid.id[1], PGUID (pwr->e.guid), sampleinfo->seq);
       return 0;
     }
     statusinfo = (qos.present & PP_STATUSINFO) ? qos.statusinfo : 0;
@@ -1947,8 +1961,6 @@ static int deliver_user_data (const struct nn_rsample_info *sampleinfo, const st
 
   if (rdguid == NULL)
   {
-    ETRACE (pwr, " %"PRId64"=>EVERYONE\n", sampleinfo->seq);
-
     /* FIXME: Retry loop, for re-delivery of rejected reliable samples. Is a
        temporary hack till throttling back of writer is implemented (with late
        acknowledgement of sample and nack). */
@@ -1963,9 +1975,9 @@ static int deliver_user_data (const struct nn_rsample_info *sampleinfo, const st
         struct ddsi_tkmap_instance *tk;
         if ((payload = new_sample_from_data (&tk, gv, sampleinfo, data_smhdr_flags, &qos, fragchain, statusinfo, tstamp, rdary[0]->topic)) != NULL)
         {
+          ETRACE (pwr, " => EVERYONE\n");
           uint32_t i = 0;
           do {
-            ETRACE (pwr, "reader "PGUIDFMT"\n", PGUID (rdary[i]->e.guid));
             if (!rhc_store (rdary[i]->rhc, &pwr_info, payload, tk))
             {
               if (pwr_locked) ddsrt_mutex_unlock (&pwr->e.lock);
@@ -2005,12 +2017,14 @@ static int deliver_user_data (const struct nn_rsample_info *sampleinfo, const st
         struct ddsi_tkmap_instance *tk;
         if ((payload = new_sample_from_data (&tk, gv, sampleinfo, data_smhdr_flags, &qos, fragchain, statusinfo, tstamp, rd->topic)) != NULL)
         {
+          ETRACE (pwr, " =>");
           do {
-            ETRACE (pwr, "reader-via-guid "PGUIDFMT"\n", PGUID (rd->e.guid));
+            ETRACE (pwr, " "PGUIDFMT, PGUID (rd->e.guid));
             (void) rhc_store (rd->rhc, &pwr_info, payload, tk);
             rd = proxy_writer_next_in_sync_reader (pwr, &it);
           } while (rd != NULL);
           free_sample_after_store (gv, payload, tk);
+          ETRACE (pwr, "\n");
         }
       }
       if (!pwr_locked) ddsrt_mutex_unlock (&pwr->e.lock);
@@ -2021,13 +2035,13 @@ static int deliver_user_data (const struct nn_rsample_info *sampleinfo, const st
   else
   {
     struct reader *rd = ephash_lookup_reader_guid (gv->guid_hash, rdguid);
-    ETRACE (pwr, " %"PRId64"=>"PGUIDFMT"%s\n", sampleinfo->seq, PGUID (*rdguid), rd ? "" : "?");
     if (rd != NULL)
     {
       struct ddsi_serdata *payload;
       struct ddsi_tkmap_instance *tk;
       if ((payload = new_sample_from_data (&tk, gv, sampleinfo, data_smhdr_flags, &qos, fragchain, statusinfo, tstamp, rd->topic)) != NULL)
       {
+        ETRACE (pwr, " =>"PGUIDFMT"\n", PGUID (*rdguid));
         /* FIXME: why look up rd,pwr again? Their states remains valid while the thread stays
            "awake" (although a delete can be initiated), and blocking like this is a stopgap
            anyway -- quite possibly to abort once either is deleted */
diff --git a/src/core/ddsi/src/q_transmit.c b/src/core/ddsi/src/q_transmit.c
index 2bdaa70..7b56ad9 100644
--- a/src/core/ddsi/src/q_transmit.c
+++ b/src/core/ddsi/src/q_transmit.c
@@ -859,6 +859,8 @@ static int insert_sample_in_whc (struct writer *wr, seqno_t seq, struct nn_plist
     const char *ttname = wr->topic ? wr->topic->type_name : "(null)";
     ppbuf[0] = '\0';
     tmp = sizeof (ppbuf) - 1;
+    if (wr->e.gv->logconfig.c.mask & DDS_LC_CONTENT)
+      ddsi_serdata_print (serdata, ppbuf, sizeof (ppbuf));
     ETRACE (wr, "write_sample "PGUIDFMT" #%"PRId64, PGUID (wr->e.guid), seq);
     if (plist != 0 && (plist->present & PP_COHERENT_SET))
       ETRACE (wr, " C#%"PRId64"", fromSN (plist->coherent_set_seqno));
diff --git a/src/ddsrt/include/dds/ddsrt/log.h b/src/ddsrt/include/dds/ddsrt/log.h
index d3fbc2b..5b70d0c 100644
--- a/src/ddsrt/include/dds/ddsrt/log.h
+++ b/src/ddsrt/include/dds/ddsrt/log.h
@@ -73,13 +73,16 @@ extern "C" {
 #define DDS_LC_WHC (16384u)
 /** Debug/trace messages related to throttling. */
 #define DDS_LC_THROTTLE (32768u)
-/** All common trace categories. */
+/** Reader history cache. */
 #define DDS_LC_RHC (65536u)
+/** Include content in traces. */
+#define DDS_LC_CONTENT (131072u)
 /** All common trace categories. */
 #define DDS_LC_ALL \
     (DDS_LC_FATAL | DDS_LC_ERROR | DDS_LC_WARNING | DDS_LC_INFO | \
      DDS_LC_CONFIG | DDS_LC_DISCOVERY | DDS_LC_DATA | DDS_LC_TRACE | \
-     DDS_LC_TIMING | DDS_LC_TRAFFIC | DDS_LC_TCP | DDS_LC_THROTTLE)
+     DDS_LC_TIMING | DDS_LC_TRAFFIC | DDS_LC_TCP | DDS_LC_THROTTLE | \
+     DDS_LC_CONTENT)
 /** @}*/
 
 #define DDS_LOG_MASK \