IO (Windows): fixes blocking forever on incomplete terminal responses

Same issue as on Unix: ffGetTerminalResponse() waits for input only before
the first ReadFile(). If the terminal answers only part of the request
(e.g. one of the two OSC 10/11 replies), the next ReadFile() blocks forever.

Wait with the same timeout before every subsequent ReadFile() as well, and
restore the console mode on that error path. While waiting, also skip
key-up records: ReadFile() returns no data for them, so one left alone in
the buffer would end the wait and the following ReadFile() would block.

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 Bugfixes:
 * Improved uptime detection on SunOS via kstat. (#2674, Uptime, SunOS)
+* Fixed substring formatting returning the remaining string when a negative end index is before the start of the string. (General)
 
 # 2.70.0
 

src/common/impl/format.c

@@ -552,7 +552,7 @@ static bool parseFormatString(FFstrbuf* buffer, const FFstrbuf* formatstr, uint3
                         if (end < 0) {
                             end = (int32_t) tempString.length + end;
                         }
-                        if ((uint32_t) end > tempString.length) {
+                        if (end >= 0 && (uint32_t) end > tempString.length) {
                             end = (int32_t) tempString.length;
                         }
                         if (end > start) {

src/common/impl/io_unix.c

@@ -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);
@@ -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";
+    const char* error = waitForTerminalResponse();
+    if (error) {
+        return error;
     }
-#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
 
     char buffer[1024];
     size_t bytesRead = 0;
@@ -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) {

src/common/impl/io_windows.c

@@ -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;
@@ -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;
@@ -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) {

tests/format.c

@@ -96,6 +96,7 @@ int main(void) {
         VERIFY("output({1~10,10})", "12345 67890", "output()");
         VERIFY("output({1~10,5})", "12345 67890", "output()");
         VERIFY("output({1~3,-3})", "12345 67890", "output(45 67)");
+        VERIFY("output({1~0,-12})", "12345 67890", "output()");
         VERIFY("output({1~-5,-3})", "12345 67890", "output(67)");
         VERIFY("output({1~-0,10})", "12345 67890", "output(12345 6789)");
         VERIFY("output({1~-3,-5})", "12345 67890", "output()");