For coverage builds, we try to link against the `gcov` library (specific to the environment). But as macOS doesn't have this library and thus doesn't have the coverage tools to generate reports, the coverage builds on that platform were failing on linking.
We actually don't need to explicitly force this linking, as the `CodeCoverage` file already has correct detection logic (currently on lines 177-193), which is invoked when the `--coverage` flag is provided:
* AppleClang: Uses `xcrun -f llvm-cov` to set `GCOV_TOOL="llvm-cov gcov"`.
* Clang: Finds `llvm-cov` to set `GCOV_TOOL="llvm-cov gcov"`.
* GCC: Finds `gcov` to set `GCOV_TOOL="gcov"`.
The `GCOV_TOOL` is then passed to `gcovr` on line 416, so the correct tool is used for processing coverage data.
This change therefore removes the `gcov` suffix from lines 473 and 475 in the `CodeCoverage.cmake` file.
The rdb module was not properly designed, which is fixed in this change. The module had three classes:
1) The abstract class `RelationalDB`.
2) The abstract class `SQLiteDatabase`, which inherited from `RelationalDB` and added some pure virtual methods.
3) The concrete class `SQLiteDatabaseImp`, which inherited from `SQLiteDatabase` and implemented all methods.
The updated code simplifies this as follows:
* The `SQLiteDatabaseImp` has become `SQLiteDatabase`, and
* The former `SQLiteDatabase `has merged with `RelationalDatabase`.
This change modularizes the `WalletDB` and `Manifest`. Note that the wallet db has nothing to do with account wallets and it stores node configuration, which is why it depends on the manifest code.
This change removes the cache in `DatabaseNodeImp` and simplifies the caching logic in `SHAMapStoreImp`. As NuDB and RocksDB internally already use caches, additional caches in the code are not very valuable or may even be unnecessary, as also confirmed during preliminary performance analyses.
In certain cases, such as when modifying headers used by many compilation units, performing a unity build is slower than when performing a regular build with `ccache` enabled. There is also a benefit to a unity build in that it can detect things such as macro redefinitions within the group of files that are compiled together as a unit. This change therefore restores the ability to perform unity builds. However, instead of running every configuration with and without unity enabled, it is now only enabled for a single configuration to maintain lower computational use.
As part of restoring the code, it became clear that currently two configurations have coverage enabled, since the check doesn't focus specifically on Debian Bookworm so it also applies to Debian Trixie. This has been fixed too in this change.
The `ManifestCache::applyManifest` function was returning early without incrementing `seq_`. `OverlayImpl `uses this sequence to identify/invalidate a cached `TMManifests` message, which is exchanged with peers on connection. Depending on network size, startup sequencing, and topology, this can cause syncing issues. This change therefore increments `seq_` when a new manifest is accepted.
