Fix handling of length_value for fixed-size temporal types after libmariadb CONC-812 change

libmariadb CONC-812 changed mysql_stmt_bind_result to initialize length_value=0 for fixed-size struct types (DATE/TIME/DATETIME/TIMESTAMP). While the MYSQL_TIME buffer is still correctly filled by ps_fetch_datetime, length_value is no longer set to sizeof(MYSQL_TIME). Use buffer_length as fallback when length_value is 0 for temporal types.

Author: rusher

src/protocol/capi/BinRowProtocolCapi.cpp

@@ -105,6 +105,19 @@ namespace capi
     }
     else {
       length = bind[index].length_value;
+      /* libmariadb CONC-812 changed mysql_stmt_bind_result to initialize
+         length_value=0 for fixed-size struct types (DATE/TIME/DATETIME/TIMESTAMP).
+         The MYSQL_TIME buffer is still correctly filled by ps_fetch_datetime, but
+         length_value is no longer set to sizeof(MYSQL_TIME). Use buffer_length
+         (which we set to sizeof(MYSQL_TIME) in the constructor) as fallback. */
+      if (length == 0 && !bind[index].is_null_value) {
+        auto bufType= bind[index].buffer_type;
+        if (bufType == MYSQL_TYPE_DATE || bufType == MYSQL_TYPE_TIME ||
+            bufType == MYSQL_TYPE_DATETIME || bufType == MYSQL_TYPE_TIMESTAMP ||
+            bufType == MYSQL_TYPE_NEWDATE) {
+          length= static_cast<uint32_t>(bind[index].buffer_length);
+        }
+      }
       fieldBuf.wrap(static_cast<char*>(bind[index].buffer), length);
       this->lastValueNull = bind[index].is_null_value ? BIT_LAST_FIELD_NULL : BIT_LAST_FIELD_NOT_NULL;
     }