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test(napi): keep node's stdout in program order in the napi-app fixture #37199

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test(napi): keep node's stdout in program order in the napi-app fixture #37199

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14c431b
test(napi): keep node's stdout in program order in the napi-app fixture
dylan-conway Aug 8, 2026
b1b09bd
ci: retrigger
dylan-conway Aug 8, 2026
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5 changes: 5 additions & 0 deletions test/napi/napi-app/main.js
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Original file line number Diff line number Diff line change
@@ -1,3 +1,8 @@
// Node writes to a piped stdout asynchronously on POSIX: after one EAGAIN every
// console.log is queued until the event loop runs while the addons' printf keeps
// writing to the fd directly. Make it blocking so output stays in program order.
if (!process.isBun) process.stdout._handle?.setBlocking?.(true);

const tests = require("./module");
if (process.argv[2] === "self") {
console.log(
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7 changes: 5 additions & 2 deletions test/napi/napi-app/utils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -13,18 +13,21 @@ class BlockingStdoutScope {
BlockingStdoutScope() {
original = fcntl(1, F_GETFL);
fcntl(1, F_SETFL, original & ~O_NONBLOCK);
setvbuf(stdout, nullptr, _IOFBF, 8192);
fflush(stdout);
// Both runtimes start with stdout unbuffered. glibc keeps the existing
// 1-byte buffer when setvbuf is given a null buffer, so pass a real one.
setvbuf(stdout, buffer, _IOFBF, sizeof(buffer));
}

~BlockingStdoutScope() {
fflush(stdout);
fcntl(1, F_SETFL, original);
setvbuf(stdout, nullptr, _IOLBF, 0);
setvbuf(stdout, nullptr, _IONBF, 0);
}

private:
int original;
inline static char buffer[8192];
};

#endif
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