PQexec infinite loop - Mailing list pgsql-bugs

we have some perl code that used a DBD::Pg statement handle after
the parent database handle had been disconnected.
by doing this we could consistently put libpq into a spin:

PQexec (conn=0x829e120,
    query=0x82a2b80 "SELECT \"login\"\n\t       FROM \"account\"\n", ' ' <repeats 15 times>, "WHERE \"id\" = '1'\n", '
'<repeats 14 times>) at fe-exec.c:1207 

(gdb) p *result
$5 = {ntups = 0, numAttributes = 0, attDescs = 0x0, tuples = 0x0,
  tupArrSize = 0, resultStatus = PGRES_FATAL_ERROR,
  cmdStatus = "\000\000\000\000 \000\000\000ÿÿÿÿgetdatabaseencoding\000\a\000\000\000 ,*\b", binary = 0, xconn =
0x829e120,noticeHook = 0, noticeArg = 0x0,  
  client_encoding = 0,
  errMsg = 0x82a2c54 "PQgetResult: Unexpected asyncStatus 145\n",
  null_field = "", curBlock = 0x82a2c50, curOffset = 45, spaceLeft = 2003}

looping in fe-exec.c:PQexec:
    while ((result = PQgetResult(conn)) != NULL)
    {
        if (result->resultStatus == PGRES_COPY_IN ||
            result->resultStatus == PGRES_COPY_OUT)
        {
            PQclear(result);
            printfPQExpBuffer(&conn->errorMessage,
                "PQexec: you gotta get out of a COPY state yourself.\n");
            /* restore blocking status */
            goto errout;
        }
        PQclear(result);
    }


result is EmptyPGresult with PGRES_FATAL_ERROR, so never NULL


PQgetResult(conn) exits at default case of:

    /* Return the appropriate thing. */
    switch (conn->asyncStatus)
    {
        case PGASYNC_IDLE:
            res = NULL;            /* query is complete */
            break;
        case PGASYNC_READY:
            res = prepareAsyncResult(conn);
            /* Set the state back to BUSY, allowing parsing to proceed. */
            conn->asyncStatus = PGASYNC_BUSY;
            break;
        case PGASYNC_COPY_IN:
            res = PQmakeEmptyPGresult(conn, PGRES_COPY_IN);
            break;
        case PGASYNC_COPY_OUT:
            res = PQmakeEmptyPGresult(conn, PGRES_COPY_OUT);
            break;
        default:
            printfPQExpBuffer(&conn->errorMessage,
                              "PQgetResult: Unexpected asyncStatus %d\n",
                              (int) conn->asyncStatus);
            res = PQmakeEmptyPGresult(conn, PGRES_FATAL_ERROR);
            break;
    }

    return res;


no idea how asyncStatus came to be 145:
(this looks like garbage to me. scribbled on by DBD::Pg ?)

(gdb) p *conn
$8 = {
  pghost = 0x40169928 " \231\026@
\231\026@\030á)\b\030á)\b0\231\026@0\231\026@8\231\026@8\231\026@@\231\026@@\231\026@H\231\026@H\231\026@P\231\026@P\231\026@X\231\026@X\231\026@`\231\026@`\231\026@h\231\026@h\231\026@p\231\026@p\231\026@x\231\026@x\231\026@\200\231\026@\200\231\026@\210\231\026@\210\231\026@\220\231\026@\220\231\026@\230\231\026@\230\231\026@ \231\026@ \231\026@¨\231\026@¨\231\026@°\231\026@°\231\026@¸\231\026@¸\231\026@À\231\026@À\231\026@È\231\026@È\231\026@Ð\231\026@Ð\231\026@Ø\231\026@Ø\231\026@à\231\026@à\231\026@"...,

  pghostaddr = 0x40169928 " \231\026@
\231\026@\030á)\b\030á)\b0\231\026@0\231\026@8\231\026@8\231\026@@\231\026@@\231\026@H\231\026@H\231\026@P\231\026@P\231\026@X\231\026@X\231\026@`\231\026@`\231\026@h\231\026@h\231\026@p\231\026@p\231\026@x\231\026@x\231\026@\200\231\026@\200\231\026@\210\231\026@\210\231\026@\220\231\026@\220\231\026@\230\231\026@\230\231\026@ \231\026@ \231\026@¨\231\026@¨\231\026@°\231\026@°\231\026@¸\231\026@¸\231\026@À\231\026@À\231\026@È\231\026@È\231\026@Ð\231\026@Ð\231\026@Ø\231\026@Ø\231\026@à\231\026@à\231\026@"...,

  pgport = 0x8290fb8 " \017)\b\200â\031\b\f )\b¸\017)\b\230â\031\b",
  pgunixsocket = 0x0, pgtty = 0x0,
  pgoptions = 0x8290fc4 "¸\017)\b\230â\031\b",
  dbName = 0x8290fac "Ä\017)\bH¼\"\b\030 )\b \017)\b\200â\031\b\f )\b¸\017)\b\230â\031\b", pguser = 0x8290fd0
"¬\017)\bhâ\031\b$ )\b",pgpass = 0x0,  
  Pfdebug = 0x0, noticeHook = 0, noticeArg = 0x0, status = CONNECTION_BAD,
  asyncStatus = 145, notifyList = 0x401698f0, sock = 1075222768, laddr = {
    sa = {sa_family = 7, sa_data = '\000' <repeats 13 times>}, in = {
      sin_family = 7, sin_port = 0, sin_addr = {s_addr = 0},
      sin_zero = "\000\000\000\000\000\000\000"}, un = {sun_family = 7,
      sun_path = '\000' <repeats 22 times>, "ÿÿÿÿ", '\000' <repeats 16 times>, "Y\000\000\000¸\230\026@¸\230\026@",
'\000'<repeats 20 times>, "\224\017)\b", '\000' <repeats 20 times>, "!\000\000\000àÝ)\b\200\230"}}, raddr = {sa = { 
      sa_family = 2, sa_data = "\0258\021\000\000\000 ã)\bhi*\b"}, in = {
      sin_family = 2, sin_port = 14357, sin_addr = {s_addr = 17},
      sin_zero = " ã)\bhi*\b"}, un = {sun_family = 2,
      sun_path = "\0258\021\000\000\000 ã)\bhi*\bÈ\000\000\000\020\000\000\000DBD::Pg::db\0009", '\000' <repeats 51
times>,"8\000\000\000\021\000\000\000test\000\230\026@\000\000\000\000\021"}}, raddr_len = 0, be_pid = 0, be_key = 16,  
  salt = "\021", lobjfuncs = 0x40169800,
  inBuffer = 0x40169868
"H\213*\b`\230\026@P4*\bP4*\bèa*\b ã)\bx\230\026@x\230\026@àÝ)\bàÝ)\b\210i*\b\210i*\b\220\230\026@\220\230\026@è\213)\bè\213)\b(Ý)\b(Ý)\b\030å)\b\030å)\b°\230\026@°\230\026@¸ß)\b¸ß)\bÀ\230\026@À\230\026@È\230\026@È\230\026@Ð\230\026@Ð\230\026@Ø\230\026@Ø\230\026@à\230\026@à\230\026@è\230\026@è\230\026@ð\230\026@ð\230\026@ø\230\026@ø\230\026@",
inBufSize= 16384,  
  inStart = 57, inCursor = 57, inEnd = 4, nonblocking = 0,
  outBuffer = 0xb <Address 0xb out of bounds>, outBufSize = 0, outCount = 0,
  result = 0x829e4c8, curTuple = 0x81d2b98, setenv_state = 4294967295,
  next_eo = 0x0, allow_ssl_try = 0 '\000', require_ssl = 0 '\000', ssl = 0x0,
  errorMessage = {
    data = 0x82a6770 "PQgetResult: Unexpected asyncStatus 145\n", len = 40,
    maxlen = 977551940}, workBuffer = {
    data = 0x3a67503a <Address 0x3a67503a out of bounds>, len = 6448186,
    maxlen = 57}, client_encoding = 0}



is it correct to just do this?
(should BAD_RESPONSE and NONFATAL_ERROR also be checked?)

    while ((result = PQgetResult(conn)) != NULL)
    {
        if (result->resultStatus == PGRES_COPY_IN ||
            result->resultStatus == PGRES_COPY_OUT)
        {
            PQclear(result);
            printfPQExpBuffer(&conn->errorMessage,
                "PQexec: you gotta get out of a COPY state yourself.\n");
            /* restore blocking status */
            goto errout;
        }
+        else if (result->resultStatus == PGRES_FATAL_ERROR)
+        {
+            PQclear(result);
+            goto errout;
+        }
        PQclear(result);
    }

(yes i know -- if DBD::Pg screwed up then it isn't PQexec's fault, but
afaics PQexec should still be checking for errors)

--
 - Gus