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make stderr unconditionally unbuffered #5967

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Merged
ab9rf merged 1 commit into from
Sep 22, 2026
+4 −0
Merged

make stderr unconditionally unbuffered #5967

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1 change: 1 addition & 0 deletions docs/changelog.txt
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Expand Up @@ -105,6 +105,7 @@ Template for new versions:
## Misc Improvements
- Added ``Coord2d`` and ``Coord3d`` C++ templates, providing a standard set operations for 2-tuples and 3-tuples of any numeric type
- Renamed the ``stockpiles`` tool tag to ``stockpile`` so it no longer collides with the `stockpiles` plugin in `gui/launcher`
- Writes to ``stderr.log`` are no longer buffered on Windows, so log output is not lost if DF crashes

## Documentation
- Document ``autodump-destroy-here``. Remove mention of ``autodump destroy`` able to revert destruction.
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3 changes: 3 additions & 0 deletions library/Core.cpp
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Expand Up @@ -1114,6 +1114,9 @@ bool Core::InitMainThread(std::filesystem::path path) {
fprintf(stderr, "dfhack: redirecting stderr to stderr.log\n");
if (!freopen("stderr.log", "w", stderr))
std::cerr << "Could not redirect stderr to stderr.log" << std::endl;
// freopen makes stderr fully buffered on Windows; restore unbuffered
// writes so that stderr.log is up to date (e.g. in the event of a crash)
setvbuf(stderr, NULL, _IONBF, 0);

std::cerr << "DFHack build: " << Version::git_description() << std::endl;
if (strlen(Version::dfhack_run_url())) {
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