line-buffer stdout so progress is visible when output is redirected - #231
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GHC block-buffers stdout when it is not a terminal, so 'Checking behavior ...' progress lines are withheld until a block fills or the process exits. Piping an equiv run to a log therefore shows nothing for minutes to hours, and a healthy run looks identical to a hung one (this cost real debugging time on a multi-hour proof). Line buffering makes progress visible without changing any output.
anjapetkovic
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Aug 7, 2026
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GHC block-buffers stdout when it is not a terminal, so 'Checking behavior ...' progress lines are withheld until a block fills or the process exits. Piping an equiv run to a log therefore shows nothing for minutes to hours, and a healthy run looks identical to a hung one (this cost real debugging time on a multi-hour proof). Line buffering makes progress visible without changing any output.