Skip writing zero sized encoding blocks to encoding file.

clients/drcachesim/tracer/instru_offline.cpp

@@ -530,20 +530,22 @@ offline_instru_t::record_instr_encodings(void *drcontext, app_pc tag_pc,
         DR_ASSERT(buf < encoding_buf_start_ + encoding_buf_sz_);
     }
 
+    DR_ASSERT(buf >= buf_start + sizeof(encoding_entry_t));
+    if (buf == buf_start + sizeof(encoding_entry_t)) {
+        // If the given ilist has no app instr, we skip writing anything to the
+        // encoding file.
+        dr_mutex_unlock(encoding_lock_);
+        return;
+    }
     encoding_entry_t *enc = reinterpret_cast<encoding_entry_t *>(buf_start);
-    DR_ASSERT(buf > buf_start);
     enc->length = buf - buf_start;
     enc->id = per_block->id;
     // We put the ARM vs Thumb mode into the modoffs to ensure proper decoding.
     enc->start_pc = reinterpret_cast<uint64_t>(
         dr_app_pc_as_jump_target(instr_get_isa_mode(instrlist_first(ilist)), tag_pc));
     log_(2, "%s: Recorded %zu bytes for id " UINT64_FORMAT_STRING " @ %p\n", __FUNCTION__,
          enc->length, enc->id, tag_pc);
-    // TODO i#2062: If the ilist does not have any app instr, we still somehow need to
-    // write an entry to the encoding file. For now we keep this behavior. This
-    // reproduces on the tool.drcacheoff.getretaddr_record_replace_retaddr test.
-    DR_ASSERT(enc->length >= sizeof(encoding_entry_t));
-    encoding_length_ += enc->length;
+    encoding_length_ += (enc->length - sizeof(encoding_entry_t));
     encoding_buf_ptr_ += enc->length;
     dr_mutex_unlock(encoding_lock_);
 }

clients/drcachesim/tracer/raw2trace.cpp

@@ -364,12 +364,12 @@ module_mapper_t::do_encoding_parsing()
     uint64_t cumulative_encoding_length = 0;
     while (map_at < map_end) {
         encoding_entry_t *entry = reinterpret_cast<encoding_entry_t *>(map_at);
-        if (entry->length < sizeof(encoding_entry_t))
+        if (entry->length <= sizeof(encoding_entry_t))
             return "Encoding file is corrupted";
         if (map_at + entry->length > map_end)
             return "Encoding file is truncated";
         cum_block_enc_len_to_encoding_id_[cumulative_encoding_length] = entry->id;
-        cumulative_encoding_length += entry->length;
+        cumulative_encoding_length += (entry->length - sizeof(encoding_entry_t));
         encodings_[entry->id] = entry;
         map_at += entry->length;
     }