fix: avoid duplicate buffered writes when IO.Process.output exec fails#13464
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kim-em merged 1 commit intoleanprover:masterfrom Apr 28, 2026
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fix: avoid duplicate buffered writes when IO.Process.output exec fails#13464kim-em merged 1 commit intoleanprover:masterfrom
IO.Process.output exec fails#13464kim-em merged 1 commit intoleanprover:masterfrom
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This PR replaces `exit(-1)` with `_exit(-1)` in the forked child branches of `lean_io_process_spawn` (the `chdir` failure and `execvp` failure paths). `exit` flushes inherited C stdio buffers, which share underlying file descriptors with the parent. If the parent had a file handle open with unflushed data, that data would be written to the file in the child and then again when the parent later flushes, resulting in duplicated output. `_exit` skips the stdio flush, so the parent's buffered writes are no longer duplicated into inherited files. Closes leanprover#13463. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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This PR replaces
exit(-1)with_exit(-1)in the forked child branches oflean_io_process_spawn(thechdirfailure andexecvpfailure paths).exitflushes inherited C stdio buffers, which share underlying file descriptors with the parent. If the parent had a file handle open with unflushed data, that data would be written to the file in the child and then again when the parent later flushes, resulting in duplicated output._exitskips the stdio flush, so the parent's buffered writes are no longer duplicated into inherited files.Closes #13463.
🤖 Prepared with Claude Code