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IO (Unix): fixes blocking forever on incomplete terminal responses #2653

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Merged
CarterLi merged 2 commits into from
Oct 28, 2026
Merged

IO (Unix): fixes blocking forever on incomplete terminal responses #2653

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85ebcd2
IO (Unix): fixes blocking forever on incomplete terminal responses
ihsandeniz Oct 15, 2026
ae2138b
IO (Windows): fixes blocking forever on incomplete terminal responses
ihsandeniz Oct 26, 2026
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57 changes: 36 additions & 21 deletions src/common/impl/io_unix.c
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Original file line number Diff line number Diff line change
Expand Up @@ -149,6 +149,32 @@ void restoreTerm(void) {
tcsetattr(ftty, TCSAFLUSH, &oldTerm);
}

static const char* waitForTerminalResponse(void) {
#ifndef __APPLE__
const int pollResult = poll(&(struct pollfd) { .fd = ftty, .events = POLLIN }, 1, FF_IO_TERM_RESP_WAIT_MS);
if (pollResult <= 0) {
FF_DEBUG("poll(/dev/tty) returned %d after %d ms: %s",
pollResult, FF_IO_TERM_RESP_WAIT_MS, pollResult == 0 ? "timed out" : strerror(errno));
return "poll(/dev/tty) timeout or failed";
}
#else
{
// On macOS, poll(/dev/tty) always returns immediately
// See also https://nathancraddock.com/blog/macos-dev-tty-polling/
fd_set rd;
FD_ZERO(&rd);
FD_SET(ftty, &rd);
const int selectResult = select(ftty + 1, &rd, nullptr, nullptr, &(struct timeval) { .tv_sec = FF_IO_TERM_RESP_WAIT_MS / 1000, .tv_usec = (FF_IO_TERM_RESP_WAIT_MS % 1000) * 1000 });
if (selectResult <= 0) {
FF_DEBUG("select(/dev/tty) returned %d after %d ms: %s",
selectResult, FF_IO_TERM_RESP_WAIT_MS, selectResult == 0 ? "timed out" : strerror(errno));
return "select(/dev/tty) timeout or failed";
}
}
#endif
return nullptr;
}

const char* ffGetTerminalResponse(const char* request, int nParams, const char* format, ...) {
if (ftty < 0) {
ftty = open("/dev/tty", O_RDWR | O_NOCTTY | O_CLOEXEC);
Expand All @@ -174,28 +200,10 @@ const char* ffGetTerminalResponse(const char* request, int nParams, const char*
ffWriteFDData(ftty, strlen(request), request);

// Give the terminal some time to respond
#ifndef __APPLE__
const int pollResult = poll(&(struct pollfd) { .fd = ftty, .events = POLLIN }, 1, FF_IO_TERM_RESP_WAIT_MS);
if (pollResult <= 0) {
FF_DEBUG("poll(/dev/tty) returned %d after %d ms: %s",
pollResult, FF_IO_TERM_RESP_WAIT_MS, pollResult == 0 ? "timed out" : strerror(errno));
return "poll(/dev/tty) timeout or failed";
}
#else
{
// On macOS, poll(/dev/tty) always returns immediately
// See also https://nathancraddock.com/blog/macos-dev-tty-polling/
fd_set rd;
FD_ZERO(&rd);
FD_SET(ftty, &rd);
const int selectResult = select(ftty + 1, &rd, nullptr, nullptr, &(struct timeval) { .tv_sec = FF_IO_TERM_RESP_WAIT_MS / 1000, .tv_usec = (FF_IO_TERM_RESP_WAIT_MS % 1000) * 1000 });
if (selectResult <= 0) {
FF_DEBUG("select(/dev/tty) returned %d after %d ms: %s",
selectResult, FF_IO_TERM_RESP_WAIT_MS, selectResult == 0 ? "timed out" : strerror(errno));
return "select(/dev/tty) timeout or failed";
}
const char* error = waitForTerminalResponse();
if (error) {
return error;
}
#endif

char buffer[1024];
size_t bytesRead = 0;
Expand All @@ -204,6 +212,13 @@ const char* ffGetTerminalResponse(const char* request, int nParams, const char*
va_start(args, format);

while (true) {
// The response may arrive in several chunks; a terminal that sends an incomplete
// response would otherwise block `read` forever
if (bytesRead > 0 && (error = waitForTerminalResponse())) {
va_end(args);
return error;
}

ssize_t nRead = read(ftty, buffer + bytesRead, sizeof(buffer) - bytesRead - 1);

if (nRead <= 0) {
Expand Down
66 changes: 43 additions & 23 deletions src/common/impl/io_windows.c
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Original file line number Diff line number Diff line change
Expand Up @@ -414,6 +414,35 @@ void ffListFilesRecursively(const char* path, bool pretty) {
listFilesRecursively(folder.length, &folder, 0, nullptr, pretty);
}

static const char* waitForTerminalResponse(HANDLE hInput) {
while (true) {
NTSTATUS status = NtWaitForSingleObject(hInput, FALSE, &(LARGE_INTEGER) { .QuadPart = (int64_t) FF_IO_TERM_RESP_WAIT_MS * -10000 });
if (status != STATUS_WAIT_0) {
FF_DEBUG("NtWaitForSingleObject() failed or timeout: %s", ffDebugNtStatus(status));
return "NtWaitForSingleObject() failed or timeout";
}

// Ignore all unexpected input events
INPUT_RECORD record;
DWORD len = 0;
if (!PeekConsoleInputW(hInput, &record, 1, &len)) {
return nullptr;
}

// Key-up events carry no input for `ReadFile`; leaving one in the buffer would make the
// wait return while the next `ReadFile` still blocks
if (
record.EventType == KEY_EVENT &&
record.Event.KeyEvent.bKeyDown &&
record.Event.KeyEvent.uChar.UnicodeChar != L'\r' &&
record.Event.KeyEvent.uChar.UnicodeChar != L'\n') {
return nullptr;
}

ReadConsoleInputW(hInput, &record, 1, &len);
}
}

const char* ffGetTerminalResponse(const char* request, int nParams, const char* format, ...) {
HANDLE hInput = GetStdHandle(STD_INPUT_HANDLE);
FF_AUTO_CLOSE_FD HANDLE hConin = INVALID_HANDLE_VALUE;
Expand All @@ -440,29 +469,10 @@ const char* ffGetTerminalResponse(const char* request, int nParams, const char*
WriteFile(hOutput, request, (DWORD) strlen(request), &bytes, nullptr);
}

while (true) {
NTSTATUS status = NtWaitForSingleObject(hInput, FALSE, &(LARGE_INTEGER) { .QuadPart = (int64_t) FF_IO_TERM_RESP_WAIT_MS * -10000 });
if (status != STATUS_WAIT_0) {
FF_DEBUG("NtWaitForSingleObject() failed or timeout: %s", ffDebugNtStatus(status));
SetConsoleMode(hInput, inputMode);
return "NtWaitForSingleObject() failed or timeout";
}

// Ignore all unexpected input events
INPUT_RECORD record;
DWORD len = 0;
if (!PeekConsoleInputW(hInput, &record, 1, &len)) {
break;
}

if (
record.EventType == KEY_EVENT &&
record.Event.KeyEvent.uChar.UnicodeChar != L'\r' &&
record.Event.KeyEvent.uChar.UnicodeChar != L'\n') {
break;
} else {
ReadConsoleInputW(hInput, &record, 1, &len);
}
const char* error = waitForTerminalResponse(hInput);
if (error) {
SetConsoleMode(hInput, inputMode);
return error;
}

va_list args;
Expand All @@ -472,6 +482,16 @@ const char* ffGetTerminalResponse(const char* request, int nParams, const char*
uint32_t bytesRead = 0;

while (true) {
// The response may arrive in several chunks; a terminal that sends an incomplete
// response would otherwise block `ReadFile` forever
if (bytesRead > 0 && (error = waitForTerminalResponse(hInput))) {
va_end(args);
if (hasInputMode) {
SetConsoleMode(hInput, inputMode);
}
return error;
}

DWORD bytes = 0;
BOOL readOk = ReadFile(hInput, buffer + bytesRead, (DWORD) (sizeof(buffer) - 1 - bytesRead), &bytes, nullptr);
if (!readOk || bytes == 0) {
Expand Down
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