file.write() streamed directly onto the target path, so a crash mid-write
left a truncated file with dangling STEP references. Serialize to a temp
file in the same directory, then atomically rename it onto the target.
- New IfcUtil::path::atomic_rename_file: std::rename on POSIX, MoveFileExW
with MOVEFILE_REPLACE_EXISTING on Windows. Unlike rename_file it never
unlinks the destination first, so there is no window where it goes missing.
- Fully in C++/swig (per aothms), so the FILE_NAME header is untouched: it
comes from the model header, not the output path (verified empirically).
- Temp lives next to the target so the rename stays on one filesystem.
- Stream is closed before the rename (Windows cannot move an open file).
- On any write error the temp is removed and the original target is intact.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>