Not a big issue, but C sources should have their language set to C so gdb knows better how to interpret the generated debug information.
@WalterBright created dlang/dmd pull request #13430 "fix Issue 22591 - importC: Debug information for C sources have DW_AT…" fixing this issue: - fix Issue 22591 - importC: Debug information for C sources have DW_AT_language set to D https://github.com/dlang/dmd/pull/13430
dlang/dmd pull request #13430 "fix Issue 22591 - importC: Debug information for C sources have DW_AT…" was merged into stable: - b9338441d708de5f147fd1d4878c8d95e67fbbb3 by Walter Bright: fix Issue 22591 - importC: Debug information for C sources have DW_AT_language set to D https://github.com/dlang/dmd/pull/13430