Progress towards mdelem pointer elimination

src/core/lib/surface/channel.c

@@ -119,7 +119,7 @@ grpc_channel *grpc_channel_create(grpc_exec_ctx *exec_ctx, const char *target,
           gpr_log(GPR_ERROR, "%s ignored: it must be a string",
                   GRPC_ARG_DEFAULT_AUTHORITY);
         } else {
-          if (channel->default_authority) {
+          if (!GRPC_MDISNULL(channel->default_authority)) {
             /* setting this takes precedence over anything else */
             GRPC_MDELEM_UNREF(exec_ctx, channel->default_authority);
           }
@@ -133,7 +133,7 @@ grpc_channel *grpc_channel_create(grpc_exec_ctx *exec_ctx, const char *target,
           gpr_log(GPR_ERROR, "%s ignored: it must be a string",
                   GRPC_SSL_TARGET_NAME_OVERRIDE_ARG);
         } else {
-          if (channel->default_authority) {
+          if (!GRPC_MDISNULL(channel->default_authority)) {
             /* other ways of setting this (notably ssl) take precedence */
             gpr_log(GPR_ERROR,
                     "%s ignored: default host already set some other way",
@@ -199,9 +199,9 @@ static grpc_call *grpc_channel_create_call_internal(
   GPR_ASSERT(!(cq != NULL && pollset_set_alternative != NULL));
 
   send_metadata[num_metadata++] = path_mdelem;
-  if (authority_mdelem != NULL) {
+  if (!GRPC_MDISNULL(authority_mdelem)) {
     send_metadata[num_metadata++] = authority_mdelem;
-  } else if (channel->default_authority != NULL) {
+  } else if (!GRPC_MDISNULL(channel->default_authority)) {
     send_metadata[num_metadata++] = GRPC_MDELEM_REF(channel->default_authority);
   }
 
@@ -236,7 +236,7 @@ grpc_call *grpc_channel_create_call(grpc_channel *channel,
                               grpc_slice_ref(method)),
       host != NULL ? grpc_mdelem_from_slices(&exec_ctx, GRPC_MDSTR_AUTHORITY,
                                              grpc_slice_ref(*host))
-                   : NULL,
+                   : GRPC_MDNULL,
       deadline);
   grpc_exec_ctx_finish(&exec_ctx);
   return call;
@@ -253,7 +253,7 @@ grpc_call *grpc_channel_create_pollset_set_call(
                               grpc_slice_ref(method)),
       host != NULL ? grpc_mdelem_from_slices(exec_ctx, GRPC_MDSTR_AUTHORITY,
                                              grpc_slice_ref(*host))
-                   : NULL,
+                   : GRPC_MDNULL,
       deadline);
 }
 
@@ -273,7 +273,7 @@ void *grpc_channel_register_call(grpc_channel *channel, const char *method,
       host ? grpc_mdelem_from_slices(
                  &exec_ctx, GRPC_MDSTR_AUTHORITY,
                  grpc_slice_intern(grpc_slice_from_copied_string(host)))
-           : NULL;
+           : GRPC_MDNULL;
   gpr_mu_lock(&channel->registered_call_mu);
   rc->next = channel->registered_calls;
   channel->registered_calls = rc;
@@ -301,8 +301,7 @@ grpc_call *grpc_channel_create_registered_call(
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   grpc_call *call = grpc_channel_create_call_internal(
       &exec_ctx, channel, parent_call, propagation_mask, completion_queue, NULL,
-      GRPC_MDELEM_REF(rc->path),
-      rc->authority ? GRPC_MDELEM_REF(rc->authority) : NULL, deadline);
+      GRPC_MDELEM_REF(rc->path), GRPC_MDELEM_REF(rc->authority), deadline);
   grpc_exec_ctx_finish(&exec_ctx);
   return call;
 }
@@ -331,14 +330,10 @@ static void destroy_channel(grpc_exec_ctx *exec_ctx, void *arg,
     registered_call *rc = channel->registered_calls;
     channel->registered_calls = rc->next;
     GRPC_MDELEM_UNREF(exec_ctx, rc->path);
-    if (rc->authority) {
-      GRPC_MDELEM_UNREF(exec_ctx, rc->authority);
-    }
+    GRPC_MDELEM_UNREF(exec_ctx, rc->authority);
     gpr_free(rc);
   }
-  if (channel->default_authority != NULL) {
-    GRPC_MDELEM_UNREF(exec_ctx, channel->default_authority);
-  }
+  GRPC_MDELEM_UNREF(exec_ctx, channel->default_authority);
   gpr_mu_destroy(&channel->registered_call_mu);
   gpr_free(channel->target);
   gpr_free(channel);
@@ -368,7 +363,7 @@ grpc_compression_options grpc_channel_compression_options(
 }
 
 grpc_mdelem grpc_channel_get_reffed_status_elem(grpc_exec_ctx *exec_ctx,
-                                                 grpc_channel *channel, int i) {
+                                                grpc_channel *channel, int i) {
   char tmp[GPR_LTOA_MIN_BUFSIZE];
   switch (i) {
     case 0:

src/core/lib/surface/server.c

@@ -739,16 +739,16 @@ static grpc_mdelem server_filter(grpc_exec_ctx *exec_ctx, void *user_data,
                                  grpc_mdelem md) {
   grpc_call_element *elem = user_data;
   call_data *calld = elem->call_data;
-  if (grpc_slice_cmp(md->key, GRPC_MDSTR_PATH) == 0) {
+  if (grpc_slice_cmp(GRPC_MDKEY(md), GRPC_MDSTR_PATH) == 0) {
     if (!calld->path_set) {
-      calld->path = grpc_slice_ref(md->value);
+      calld->path = grpc_slice_ref(GRPC_MDVALUE(md));
     }
-    return NULL;
-  } else if (grpc_slice_cmp(md->key, GRPC_MDSTR_AUTHORITY) == 0) {
+    return GRPC_MDNULL;
+  } else if (grpc_slice_cmp(GRPC_MDKEY(md), GRPC_MDSTR_AUTHORITY) == 0) {
     if (!calld->host_set) {
-      calld->host = grpc_slice_ref(md->value);
+      calld->host = grpc_slice_ref(GRPC_MDVALUE(md));
     }
-    return NULL;
+    return GRPC_MDNULL;
   }
   return md;
 }

src/core/lib/transport/metadata.c

@@ -313,8 +313,8 @@ size_t grpc_mdelem_get_size_in_hpack_table(grpc_mdelem elem) {
 }
 
 grpc_mdelem grpc_mdelem_ref(grpc_mdelem gmd DEBUG_ARGS) {
+  if (gmd.payload == NULL || is_mdelem_static(gmd)) return gmd;
   internal_metadata *md = (internal_metadata *)gmd.payload;
-  if (is_mdelem_static(gmd)) return gmd;
 #ifdef GRPC_METADATA_REFCOUNT_DEBUG
   gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG,
           "ELM   REF:%p:%zu->%zu: '%s' = '%s'", (void *)md,
@@ -333,9 +333,8 @@ grpc_mdelem grpc_mdelem_ref(grpc_mdelem gmd DEBUG_ARGS) {
 }
 
 void grpc_mdelem_unref(grpc_exec_ctx *exec_ctx, grpc_mdelem gmd DEBUG_ARGS) {
+  if (gmd.payload == NULL || is_mdelem_static(gmd)) return;
   internal_metadata *md = (internal_metadata *)gmd.payload;
-  if (!md) return;
-  if (is_mdelem_static(gmd)) return;
 #ifdef GRPC_METADATA_REFCOUNT_DEBUG
   gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG,
           "ELM UNREF:%p:%zu->%zu: '%s' = '%s'", (void *)md,

src/core/lib/transport/metadata.h

@@ -127,7 +127,7 @@ void grpc_mdelem_unref(grpc_exec_ctx *exec_ctx, grpc_mdelem md);
 
 /* We add 32 bytes of padding as per RFC-7540 section 6.5.2. */
 #define GRPC_MDELEM_LENGTH(e)                                                  \
-  (GRPC_SLICE_LENGTH(GRPC_MDKEY((e))) + GRPC_SLICE_LENGTH(MRPC_MDVALUE((e))) + \
+  (GRPC_SLICE_LENGTH(GRPC_MDKEY((e))) + GRPC_SLICE_LENGTH(GRPC_MDVALUE((e))) + \
    32)
 
 #define GRPC_MDSTR_KV_HASH(k_hash, v_hash) (GPR_ROTL((k_hash), 2) ^ (v_hash))

src/core/lib/transport/metadata_batch.c

@@ -52,7 +52,7 @@ static void assert_valid_list(grpc_mdelem_list *list) {
   GPR_ASSERT((list->head == list->tail) == (list->head->next == NULL));
 
   for (l = list->head; l; l = l->next) {
-    GPR_ASSERT(l->md);
+    GPR_ASSERT(!GRPC_MDISNULL(l->md));
     GPR_ASSERT((l->prev == NULL) == (l == list->head));
     GPR_ASSERT((l->next == NULL) == (l == list->tail));
     if (l->next) GPR_ASSERT(l->next->prev == l);
@@ -83,14 +83,14 @@ void grpc_metadata_batch_destroy(grpc_exec_ctx *exec_ctx,
 void grpc_metadata_batch_add_head(grpc_metadata_batch *batch,
                                   grpc_linked_mdelem *storage,
                                   grpc_mdelem elem_to_add) {
-  GPR_ASSERT(elem_to_add);
+  GPR_ASSERT(!GRPC_MDISNULL(elem_to_add));
   storage->md = elem_to_add;
   grpc_metadata_batch_link_head(batch, storage);
 }
 
 static void link_head(grpc_mdelem_list *list, grpc_linked_mdelem *storage) {
   assert_valid_list(list);
-  GPR_ASSERT(storage->md);
+  GPR_ASSERT(!GRPC_MDISNULL(storage->md));
   storage->prev = NULL;
   storage->next = list->head;
   if (list->head != NULL) {
@@ -110,14 +110,14 @@ void grpc_metadata_batch_link_head(grpc_metadata_batch *batch,
 void grpc_metadata_batch_add_tail(grpc_metadata_batch *batch,
                                   grpc_linked_mdelem *storage,
                                   grpc_mdelem elem_to_add) {
-  GPR_ASSERT(elem_to_add);
+  GPR_ASSERT(!GRPC_MDISNULL(elem_to_add));
   storage->md = elem_to_add;
   grpc_metadata_batch_link_tail(batch, storage);
 }
 
 static void link_tail(grpc_mdelem_list *list, grpc_linked_mdelem *storage) {
   assert_valid_list(list);
-  GPR_ASSERT(storage->md);
+  GPR_ASSERT(!GRPC_MDISNULL(storage->md));
   storage->prev = list->tail;
   storage->next = NULL;
   storage->reserved = NULL;
@@ -157,7 +157,7 @@ void grpc_metadata_batch_filter(grpc_exec_ctx *exec_ctx,
     grpc_mdelem orig = l->md;
     grpc_mdelem filt = filter(exec_ctx, user_data, orig);
     next = l->next;
-    if (filt == NULL) {
+    if (GRPC_MDISNULL(filt)) {
       if (l->prev) {
         l->prev->next = l->next;
       }
@@ -172,7 +172,7 @@ void grpc_metadata_batch_filter(grpc_exec_ctx *exec_ctx,
       }
       assert_valid_list(&batch->list);
       GRPC_MDELEM_UNREF(exec_ctx, l->md);
-    } else if (filt != orig) {
+    } else if (!grpc_mdelem_eq(filt, orig)) {
       GRPC_MDELEM_UNREF(exec_ctx, orig);
       l->md = filt;
     }
@@ -184,7 +184,7 @@ void grpc_metadata_batch_filter(grpc_exec_ctx *exec_ctx,
 
 static grpc_mdelem no_metadata_for_you(grpc_exec_ctx *exec_ctx, void *user_data,
                                        grpc_mdelem elem) {
-  return NULL;
+  return GRPC_MDNULL;
 }
 
 void grpc_metadata_batch_clear(grpc_exec_ctx *exec_ctx,