I often compile old versions of MySQL, MariaDB, Postgres and RocksDB in my search for performance regressions. Compiling is easy with Postgres as they do a great job at avoiding compilation warnings and I never encounter broken builds. Certainly the community gets the credit for this, but I suspect their task is easier because they use C. This started as a LinkedIn post.

I expect people to disagree, and I am far from a C++ expert, but here goes ...

tl;dr - if you maintain widely used header files (widely used by C++ projects) consider not removing that include that you don’t really need (like <cstdint>) because such removal is likely to break builds for older releases of projects that use your include.

I have more trouble compiling older releases of C++ projects. For MySQL I have a directory in github that includes patches that must be applied. And for MySQL I have to patch all 5.6 versions, 5.7 versions up to 5.7.33 and 8.0 versions up to 8.0.23. The most common reason for the patch is missing C++ includes (like <cstdint>).

For RocksDB with gcc I don’t have to patch files but I need to use gcc-11 for RocksDB 6.x and gcc-12 for RocksDB 7.x.

For RocksDB with clang I don’t have to patch files for RocksDB 8.x, 9.x and 10.x while I do have to patch 6.x and 7.x. For RocksDB 7.10 I need to edit two files to add <cstdint>. The files are:

• table/block_based/data_block_hash_index.h
• util/string_util.h

All of this is true for Ubuntu 24.04 with clang 18.1.3 and gcc 13.3.0.