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

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

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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) {
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