From 0ff9050eb3a18dd9f9dba4d4fb6e95bb9e3c87f2 Mon Sep 17 00:00:00 2001 From: catbot Date: Mon, 1 Jun 2026 14:42:33 +0000 Subject: [PATCH] fix: line-buffer stdout when redirected so progress/readiness lines flush MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When crafter-build's stdout is not a TTY (redirected to a file or pipe) the C runtime defaults to full (block) buffering. The progress path is TTY-aware and the in-place redraw flushes explicitly, but the non-TTY append path (`[N/M]` lines), Finalize()'s `Built N steps` line and the `-r` server's `listening on port :N` line all go through block-buffered stdout with no flush. They accumulate in the buffer and only spill at ~4KB boundaries. On a normal build this is hidden because the C runtime flushes stdout at exit. Under `-r` the process never exits — it blocks in its serve loop — so the trailing buffer is never flushed: a redirected log freezes mid-build (or sits at 0 bytes) even though the build finished and the server is already answering. Any tooling that polls the log for `Built …` / `listening …` / `[N/N]` hangs forever. This is the real cause of the frozen log misdiagnosed as a build deadlock in #16. Fix: switch stdout to line buffering at the very top of main(), before any output, only when stdout is not a terminal. Every `\n` then flushes, so the markers reach a redirected log immediately. No behaviour change on a TTY. Kept self-contained in main.cpp using system headers (isatty + setvbuf) rather than a new Crafter::Progress export: the self-hosting exe build compiles main.cpp against the installed/cached Crafter.Build module BMIs, which shadow the freshly built local ones, so a new interface symbol would not be visible without reinstalling crafter-build first. Resolves #18 Co-Authored-By: Claude Opus 4.8 --- implementations/main.cpp | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/implementations/main.cpp b/implementations/main.cpp index 4c7aa06..f84c304 100644 --- a/implementations/main.cpp +++ b/implementations/main.cpp @@ -17,9 +17,33 @@ License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ +#include +#if defined(_WIN32) + #include + #ifndef STDOUT_FILENO + #define STDOUT_FILENO _fileno(stdout) + #endif + #define CRAFTER_MAIN_ISATTY _isatty +#else + #include + #define CRAFTER_MAIN_ISATTY isatty +#endif + import std; import Crafter.Build; int main(int argc, char** argv) { + // Line-buffer stdout when it is not a terminal. Must run before any stdout + // write. When stdout is a regular file or pipe the C runtime defaults to + // full (block) buffering, so the append-only progress lines ("[N/M]") and + // the trailing "Built … steps" / "listening on port …" lines would sit in + // the buffer and never reach a redirected log — fatal for tooling that + // polls the log for a readiness marker, and worst under -r where the + // process blocks in its serve loop and never returns to flush. A TTY is + // already line-buffered and its in-place redraw path flushes explicitly, so + // only adjust when redirected. + if (CRAFTER_MAIN_ISATTY(STDOUT_FILENO) == 0) { + std::setvbuf(stdout, nullptr, _IOLBF, 0); + } return Crafter::Run(argc, argv); }