# Compilation error with clang 15

**URL:** <https://forums.foundationdb.org/t/compilation-error-with-clang-15/3880>\
**Category:** Development\
**Created:** [March 30, 2023, 12:52pm UTC](https://forums.foundationdb.org/t/compilation-error-with-clang-15/3880 "2023-03-30T12:52:19Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![osamarin](https://sea1.discourse-cdn.com/foundationdb/user_avatar/forums.foundationdb.org/osamarin/32/905_2.png) [@osamarin](https://forums.foundationdb.org/u/osamarin)\
**Post date:** [March 30, 2023, 12:52pm UTC](https://forums.foundationdb.org/t/compilation-error-with-clang-15/3880/1 "2023-03-30T12:52:19Z")

</div>

Hello, all and foundationdb developers.

I’m trying to compile foundationdb 7.1.29 from sources with the clang 15 compiler and I receive the following error:

```auto
/home/oleg/git/xdb/FoundationDb/fdbserver/KeyValueStoreRocksDB.actor.cpp:272:34: error: assigning to 'rocksdb::Temperature' from incompatible type 'uint8_t' (aka 'unsigned char')
                liveFileMetaData.temperature = static_cast<uint8_t>(fileMetaData.temperature);
                                               ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

```

The reason is that `rocksdb::Temperature` is not uint8\_t, but it is an enum class based on uint8\_t. New versions of clang compiler prohibit conversion from a base type to enum by default.

Because both `fileMetaData.temperature` and `liveFileMetaData.temperature` have the same type `rocksdb::Temperature`, the intermediate casting to uint8\_t is not required, and eliminating it solves the compilation problem.

A short patch is here.

```auto
diff --git a/fdbserver/KeyValueStoreRocksDB.actor.cpp b/fdbserver/KeyValueStoreRocksDB.actor.cpp
index 6da346742..83f7697bf 100644
--- a/fdbserver/KeyValueStoreRocksDB.actor.cpp
+++ b/fdbserver/KeyValueStoreRocksDB.actor.cpp
@@ -269,7 +269,7 @@ void populateMetaData(CheckpointMetaData* checkpoint, const rocksdb::ExportImpor
 		liveFileMetaData.being_compacted = fileMetaData.being_compacted;
 		liveFileMetaData.num_entries = fileMetaData.num_entries;
 		liveFileMetaData.num_deletions = fileMetaData.num_deletions;
- liveFileMetaData.temperature = static_cast<uint8_t>(fileMetaData.temperature);
+ liveFileMetaData.temperature = fileMetaData.temperature;
 		liveFileMetaData.oldest_blob_file_number = fileMetaData.oldest_blob_file_number;
 		liveFileMetaData.oldest_ancester_time = fileMetaData.oldest_ancester_time;
 		liveFileMetaData.file_creation_time = fileMetaData.file_creation_time;

```