Problem with boolean type in Informix via ODBC

Question

Hello,
I'm connecting to an Informix database from an Oracle database via the ODBC Gateway. The connection works fine.
However, when I select a boolean type column from a table in the Informix database, nothing is returned and I get the following error:
SQL> select "stat" from bt@informix;
ERROR:
ORA-28500: connection from ORACLE to a non-Oracle system returned this message:
[Informix][Informix ODBC Driver]Restricted data type attribute violation.
{07006,NativeErr = -11013}
ORA-02063: preceding 2 lines from INFORMIX
no rows selected
Selecting a boolean type column with isql works fine. Other column types work from Oracle.
Can anyone help me resolve this issue? Please find configuration details and traces below.
Software stack:
Informix Database: Enterprise Edition 12.10 for Linux x86_64
Informix ODBC driver: Informix Client SDK Developer Edition 4.10 for Linux 64-bit
Oracle Database: Enterprise Edition 11.2.0.1.0 64-bit (Oracle Linux 6.6 64-bit)
UnixODBC: 2.3.2 x86_64
odbcinst.ini:
[Informix]
Driver=/opt/IBM/informix/lib/cli/libifcli.so
Setup=/opt/IBM/informix/lib/cli/libifcli.so
APILevel=1
ConnectFunctions=YYY
DriverODBCVer=03.51
FileUsage=0
SQLLevel=1
smProcessPerConnect=Y
[ODBC]
TraceFile=/tmp/odbc.log
Trace = Yes
odbc.ini:
[ol_informix1210]
Driver=Informix
Description=Test connection
Database=sysutils
LogonID=informix
pwd=informix
Servername=ol_informix1210
CursorBehavior=0
DB_LOCALE=en_us.8859-1
TRANSLATIONDLL=/opt/IBM/informix/lib/esql/igo4a304.so
[ODBC]
UNICODE=UCS-2
; Trace file Section
Trace=1
TraceFile=/tmp/odbctrace.out
InstallDir=/opt/IBM/informix
TRACEDLL=idmrs09a.so
Oracle Gateway init.ora:
HS_FDS_CONNECT_INFO=ol_informix1210
HS_FDS_SHAREABLE_NAME=/usr/local/lib/libodbc.so
HS_FDS_TRACE_LEVEL=debug
HS_LANGUAGE=AMERICAN_AMERICA.WE8ISO8859P1
Oracle Gateway trace:
Entered hgoftch, cursor id 1 at 2015/04/14-12:22:03
hgoftch, line 130: Printing hoada @ 0x2007fe0
MAX:1, ACTUAL:1, BRC:100, WHT=5 (SELECT_LIST)
hoadaMOD bit-values found (0x20:NEGATIVE_HOADADTY)
DTY     NULL-OK  LEN  MAXBUFLEN   PR/SC  CST IND MOD NAME
-7 BIT Y          1          1   0/  0    0   0  20 stat
Performing delayed open.
SQLBindCol: column 1, cdatatype: -28, bflsz: 1
Entered hgopoer at 2015/04/14-12:22:03
hgopoer, line 233: got native error -11013 and sqlstate 07006; message follows...
[Informix][Informix ODBC Driver]Restricted data type attribute violation. {07006,NativeErr = -11013}
Exiting hgopoer, rc=0 at 2015/04/14-12:22:03
hgoftch, line 730: calling SQLFetch got sqlstate 07006
0 rows fetched
Exiting hgoftch, rc=28500 at 2015/04/14-12:22:03 with error ptr FILE:hgoftch.c LINE:730 FUNCTION:hgoftch() ID:Fetch resultset data
ODBC trace:
[ODBC][11041][1429005970.973443][SQLPrepare.c][196]
                Entry:
                        Statement = 0x276ecb0
                        SQL = [SELECT A1. stat  FROM  BT  A1][length = 29]
[ODBC][11041][1429005970.973914][SQLPrepare.c][371]
                Exit:[SQL_SUCCESS]
[ODBC][11041][1429005970.973940][SQLNumResultCols.c][156]
                Entry:
                        Statement = 0x276ecb0
                        Column Count = 0x26f5868
[ODBC][11041][1429005970.973970][SQLNumResultCols.c][248]
                Exit:[SQL_SUCCESS]
                        Count = 0x26f5868 -> 1
[ODBC][11041][1429005970.974097][SQLDescribeCol.c][247]
                Entry:
                        Statement = 0x276ecb0
                        Column Number = 1
                        Column Name = 0x7fffc3ff2d90
                        Buffer Length = 31
                        Name Length = 0x7fffc3ff2ed4
                        Data Type = 0x7fffc3ff2ed8
                        Column Size = 0x7fffc3ff2e70
                        Decimal Digits = 0x7fffc3ff2edc
                        Nullable = 0x7fffc3ff2ee0
[ODBC][11041][1429005970.974140][SQLDescribeCol.c][501]
               Exit:[SQL_SUCCESS]               
                        Column Name = [stat]               
                        Data Type = 0x7fffc3ff2ed8 -> -7               
                        Column Size = 0x7fffc3ff2e70 -> 1               
                        Decimal Digits = 0x7fffc3ff2edc -> 0               
                        Nullable = 0x7fffc3ff2ee0 -> 1
[ODBC][11041][1429005970.974192][SQLSetStmtAttr.c][265]
                Entry:
                        Statement = 0x276ecb0
                        Attribute = SQL_ATTR_ROW_ARRAY_SIZE
                        Value = 0x64
                        StrLen = 0
[ODBC][11041][1429005970.974218][SQLSetStmtAttr.c][925]
                Exit:[SQL_SUCCESS]
[ODBC][11041][1429005970.974230][SQLSetStmtAttr.c][265]
                Entry:
                        Statement = 0x276ecb0
                        Attribute = SQL_ATTR_ROW_BIND_TYPE
                        Value = (nil)
                        StrLen = -5
[ODBC][11041][1429005970.974249][SQLSetStmtAttr.c][925]
                Exit:[SQL_SUCCESS]
[ODBC][11041][1429005970.974837][SQLExecute.c][187]
                Entry:
                        Statement = 0x276ecb0
[ODBC][11041][1429005970.975231][SQLExecute.c][348]
                Exit:[SQL_SUCCESS]
[ODBC][11041][1429005970.975255][SQLSetStmtAttr.c][265]
                Entry:
                        Statement = 0x276ecb0
                        Attribute = SQL_ATTR_ROW_STATUS_PTR
                        Value = 0x27f5b78
                        StrLen = -4
[ODBC][11041][1429005970.975280][SQLSetStmtAttr.c][925]
                Exit:[SQL_SUCCESS]
[ODBC][11041][1429005970.975291][SQLSetStmtAttr.c][265]
                Entry:
                        Statement = 0x276ecb0
                        Attribute = SQL_ATTR_ROWS_FETCHED_PTR
                        Value = 0x26f5850
                        StrLen = -4
[ODBC][11041][1429005970.975311][SQLSetStmtAttr.c][925]
                Exit:[SQL_SUCCESS]
[ODBC][11041][1429005970.975326][SQLBindCol.c][236]
                Entry:
                        Statement = 0x276ecb0
                        Column Number = 1
                        Target Type = -28 SQL_C_UTINYINT
                        Target Value = 0x27f5af8
                        Buffer Length = 1
                        StrLen Or Ind = 0x27f5eb8
[ODBC][11041][1429005970.975349][SQLBindCol.c][341]
                Exit:[SQL_SUCCESS]
[ODBC][11041][1429005970.975367][SQLFetch.c][162]
                Entry:
                        Statement = 0x276ecb0
[ODBC][11041][1429005970.975455][SQLFetch.c][348]
                Exit:[SQL_ERROR]
                DIAG [07006] [Informix][Informix ODBC Driver]Restricted data type attribute violation.
[ODBC][11041][1429005970.975574][SQLGetDiagRec.c][758]
               Entry:
                        Statement = 0x276ecb0
                        Rec Number = 1
                        SQLState = 0x7fffc3ff2e20
                        Native = 0x7fffc3ff2c14
                        Message Text = 0x7fffc3ff2c20
                        Buffer Length = 510
                        Text Len Ptr = 0x7fffc3ff2e70
[ODBC][11041][1429005970.975615][SQLGetDiagRec.c][795]
                Exit:[SQL_SUCCESS]
                        SQLState = 07006
                        Native = 0x7fffc3ff2c14 -> -11013
                        Message Text = [[Informix][Informix ODBC Driver]Restricted data type attribute violation.]
[ODBC][11041][1429005970.975642][SQLGetDiagRec.c][758]
                Entry:
                        Statement = 0x276ecb0
                        Rec Number = 2
                        SQLState = 0x7fffc3ff2e20
                        Native = 0x7fffc3ff2c14
                        Message Text = 0x7fffc3ff2c20
                     Message Text = 0x7fffc3ff2c20
                        Buffer Length = 510
                        Text Len Ptr = 0x7fffc3ff2e70
[ODBC][11041][1429005970.975667][SQLGetDiagRec.c][795]
                Exit:[SQL_NO_DATA]

Answer 1

Here are my findings after consulting the unixODBC mailing list and the IBM documentation.
There are several levels of data types at play here: native Informix SQL types, Informix ODBC driver SQL types and Informix ODBC driver C types (as well as standard C types).
According to the Informix documentation (http://www-01.ibm.com/support/knowledgecenter/SSGU8G_11.70.0/com.ibm.odbc.doc/ids_odbc_108.htm), the ODBC driver SQL type for the native boolean type is SQL_BIT.
The traces show that the ODBC SQL type is SQL_BIT (type code -7) and that this should be converted into the SQL_C_UTINYINT ODBC C type (type code -28).
Oracle ODBC Gateway trace:
DTY    NULL-OK  LEN  MAXBUFLEN  PR/SC  CST IND MOD NAME
-7 BIT Y          1          1  0/  0    0  0  20 stat
Performing delayed open.
SQLBindCol: column 1, cdatatype: -28, bflsz: 1
unixODBC trace:
ODBC][11041][1429005970.975326][SQLBindCol.c][236]
                Entry:
                        Statement = 0x276ecb0
                        Column Number = 1
                       Target Type = -28 SQL_C_UTINYINT
                        Target Value = 0x27f5af8
                        Buffer Length = 1
                        StrLen Or Ind = 0x27f5eb8
[ODBC][11041][1429005970.975349][SQLBindCol.c][341]
Oracle tries to bind the SQL_BIT type column to a buffer of SQL_C_UTINYINT type, which requires a conversion from SQL_BIT to SQL_C_UTINYINT  that is apparently not supported by the Informix ODBC Driver.
According to the documentation (http://www-01.ibm.com/support/knowledgecenter/SSGU8G_11.70.0/com.ibm.odbc.doc/ids_odbc_108.htm) the Informix ODBC driver can only convert the SQL_BIT ODBC SQL type into SQL_C_BINARY, SQL_C_BIT and SQL_C_CHAR ODBC C types. (The ODBC C types are in turn converted into standard C types, for example the SQL_C_BIT type is converted into UCHAR which is a typedef for the standard C type unsigned char.)
A possible workaround could be to tell Informix to present boolean as a different ODBC SQL type, for example SQL_CHAR (as it would be possible with PostgreSQL by setting BoolAsCharater=1 in odbc.ini), but Informix only seems to supports the SQL_BIT ODBC SQL type.
A cumbersome workaround is to use the Gateway's pass-through feature that allows a query to be passed to Informix as is, which in turn allows us to cast the boolean field into a character field:
SQL> set serveroutput on
SQL> r
  1  DECLARE
  2    val  VARCHAR2(1);
  3    c    INTEGER;
  4    nr  INTEGER;
  5  BEGIN
  6    c := DBMS_HS_PASSTHROUGH.OPEN_CURSOR@informix;
  7    DBMS_HS_PASSTHROUGH.PARSE@informix(c,'select cast (stat as character) from bt');
  8    LOOP
  9    nr := DBMS_HS_PASSTHROUGH.FETCH_ROW@informix(c);
10    EXIT WHEN nr = 0;
11    DBMS_HS_PASSTHROUGH.GET_VALUE@informix(c, 1, val);
12    DBMS_OUTPUT.PUT_LINE(val);
13    END LOOP;
14    DBMS_HS_PASSTHROUGH.CLOSE_CURSOR@informix(c);
15  END;
16*
t
f
PL/SQL procedure successfully completed
Easier solutions are still welcome.