Clean up a number of bogosities around pltcl's handling of the Tcl "result":

1. Directly reading interp->result is deprecated in Tcl 8.0 and later;
you're supposed to use Tcl_GetStringResult.  This code finally broke with
Tcl 8.5, because Tcl_GetVar can now have side-effects on interp->result even
though it preserves the logical state of the result.  (There's arguably a
Tcl issue here, because Tcl_GetVar could invalidate the pointer result of a
just-preceding Tcl_GetStringResult, but I doubt the Tcl guys will see it as
a bug.)

2. We were being sloppy about the encoding of the result: some places would
push database-encoding data into the Tcl result, which should not happen,
and we were assuming that any error result coming back from Tcl was in the
database encoding, which is not a good assumption.

3. There were a lot of calls of Tcl_SetResult that uselessly specified
TCL_VOLATILE for constant strings.  This is only a minor performance issue,
but I fixed it in passing since I had to look at all the calls anyway.

#2 is a live bug regardless of which Tcl version you are interested in,
so back-patch even to branches that are unlikely to be used with Tcl 8.5.
I went back as far as 8.0, which is as far as the patch applied easily;
7.4 was using a different error processing scheme that has got its own
problems :-(

diff --git a/src/pl/tcl/pltcl.c b/src/pl/tcl/pltcl.c
index c7bb416..e9fdf9f 100644 (file)
--- a/src/pl/tcl/pltcl.c
+++ b/src/pl/tcl/pltcl.c
@@ -2,7 +2,7 @@
  * pltcl.c             - PostgreSQL support for Tcl as
  *                               procedural language (PL)
  *
- *       $PostgreSQL: pgsql/src/pl/tcl/pltcl.c,v 1.120 2008/05/12 00:00:54 alvherre Exp $
+ *       $PostgreSQL: pgsql/src/pl/tcl/pltcl.c,v 1.121 2008/06/17 00:52:43 tgl Exp $
  *
  **********************************************************************/
 
@@ -36,6 +36,11 @@
        ((TCL_MAJOR_VERSION > maj) || \
         (TCL_MAJOR_VERSION == maj && TCL_MINOR_VERSION >= min))
 
+/* In Tcl >= 8.0, really not supposed to touch interp->result directly */
+#if !HAVE_TCL_VERSION(8,0)
+#define Tcl_GetStringResult(interp)  ((interp)->result)
+#endif
+
 #if defined(UNICODE_CONVERSION) && HAVE_TCL_VERSION(8,1)
 
 #include "mb/pg_wchar.h"
@@ -134,6 +139,8 @@ static Datum pltcl_func_handler(PG_FUNCTION_ARGS);
 
 static HeapTuple pltcl_trigger_handler(PG_FUNCTION_ARGS);
 
+static void throw_tcl_error(Tcl_Interp *interp, const char *proname);
+
 static pltcl_proc_desc *compile_pltcl_function(Oid fn_oid, Oid tgreloid);
 
 static int pltcl_elog(ClientData cdata, Tcl_Interp *interp,
@@ -224,7 +231,7 @@ pltcl_WaitForEvent(Tcl_Time *timePtr)
 {
        return 0;
 }
-#endif   /* HAVE_TCL_VERSION(8,2) */
+#endif   /* HAVE_TCL_VERSION(8,4) */
 
 
 /*
@@ -632,16 +639,7 @@ pltcl_func_handler(PG_FUNCTION_ARGS)
         * Check for errors reported by Tcl.
         ************************************************************/
        if (tcl_rc != TCL_OK)
-       {
-               UTF_BEGIN;
-               ereport(ERROR,
-                               (errmsg("%s", interp->result),
-                                errcontext("%s\nin PL/Tcl function \"%s\"",
-                                                       UTF_U2E(Tcl_GetVar(interp, "errorInfo",
-                                                                                          TCL_GLOBAL_ONLY)),
-                                                       prodesc->user_proname)));
-               UTF_END;
-       }
+               throw_tcl_error(interp, prodesc->user_proname);
 
        /************************************************************
         * Disconnect from SPI manager and then create the return
@@ -649,8 +647,8 @@ pltcl_func_handler(PG_FUNCTION_ARGS)
         * this must not be allocated in the SPI memory context
         * because SPI_finish would free it).  But don't try to call
         * the result_in_func if we've been told to return a NULL;
-        * the contents of interp->result may not be a valid value of
-        * the result type in that case.
+        * the Tcl result may not be a valid value of the result type
+        * in that case.
         ************************************************************/
        if (SPI_finish() != SPI_OK_FINISH)
                elog(ERROR, "SPI_finish() failed");
@@ -664,7 +662,7 @@ pltcl_func_handler(PG_FUNCTION_ARGS)
        {
                UTF_BEGIN;
                retval = InputFunctionCall(&prodesc->result_in_func,
-                                                                  UTF_U2E(interp->result),
+                                                                  UTF_U2E((char *) Tcl_GetStringResult(interp)),
                                                                   prodesc->result_typioparam,
                                                                   -1);
                UTF_END;
@@ -695,6 +693,7 @@ pltcl_trigger_handler(PG_FUNCTION_ARGS)
        Datum      *modvalues;
        char       *modnulls;
        int                     ret_numvals;
+       CONST84 char *result;
        CONST84 char **ret_values;
 
        /* Connect to SPI manager */
@@ -864,37 +863,35 @@ pltcl_trigger_handler(PG_FUNCTION_ARGS)
         * Check for errors reported by Tcl.
         ************************************************************/
        if (tcl_rc != TCL_OK)
-       {
-               UTF_BEGIN;
-               ereport(ERROR,
-                               (errmsg("%s", interp->result),
-                                errcontext("%s\nin PL/Tcl function \"%s\"",
-                                                       UTF_U2E(Tcl_GetVar(interp, "errorInfo",
-                                                                                          TCL_GLOBAL_ONLY)),
-                                                       prodesc->user_proname)));
-               UTF_END;
-       }
+               throw_tcl_error(interp, prodesc->user_proname);
 
        /************************************************************
         * The return value from the procedure might be one of
-        * the magic strings OK or SKIP or a list from array get
+        * the magic strings OK or SKIP or a list from array get.
+        * We can check for OK or SKIP without worrying about encoding.
         ************************************************************/
        if (SPI_finish() != SPI_OK_FINISH)
                elog(ERROR, "SPI_finish() failed");
 
-       if (strcmp(interp->result, "OK") == 0)
+       result = Tcl_GetStringResult(interp);
+
+       if (strcmp(result, "OK") == 0)
                return rettup;
-       if (strcmp(interp->result, "SKIP") == 0)
+       if (strcmp(result, "SKIP") == 0)
                return (HeapTuple) NULL;
 
        /************************************************************
         * Convert the result value from the Tcl interpreter
         * and setup structures for SPI_modifytuple();
         ************************************************************/
-       if (Tcl_SplitList(interp, interp->result,
+       if (Tcl_SplitList(interp, result,
                                          &ret_numvals, &ret_values) != TCL_OK)
+       {
+               UTF_BEGIN;
                elog(ERROR, "could not split return value from trigger: %s",
-                        interp->result);
+                        UTF_U2E(Tcl_GetStringResult(interp)));
+               UTF_END;
+       }
 
        /* Use a TRY to ensure ret_values will get freed */
        PG_TRY();
@@ -995,6 +992,36 @@ pltcl_trigger_handler(PG_FUNCTION_ARGS)
 
 
 /**********************************************************************
+ * throw_tcl_error     - ereport an error returned from the Tcl interpreter
+ **********************************************************************/
+static void
+throw_tcl_error(Tcl_Interp *interp, const char *proname)
+{
+       /*
+        * Caution is needed here because Tcl_GetVar could overwrite the
+        * interpreter result (even though it's not really supposed to),
+        * and we can't control the order of evaluation of ereport arguments.
+        * Hence, make real sure we have our own copy of the result string
+        * before invoking Tcl_GetVar.
+        */
+       char       *emsg;
+       char       *econtext;
+
+       UTF_BEGIN;
+       emsg = pstrdup(UTF_U2E(Tcl_GetStringResult(interp)));
+       UTF_END;
+       UTF_BEGIN;
+       econtext = UTF_U2E((char *) Tcl_GetVar(interp, "errorInfo",
+                                                                                  TCL_GLOBAL_ONLY));
+       ereport(ERROR,
+                       (errmsg("%s", emsg),
+                        errcontext("%s\nin PL/Tcl function \"%s\"",
+                                               econtext, proname)));
+       UTF_END;
+}
+
+
+/**********************************************************************
  * compile_pltcl_function      - compile (or hopefully just look up) function
  *
  * tgreloid is the OID of the relation when compiling a trigger, or zero
@@ -1319,8 +1346,10 @@ compile_pltcl_function(Oid fn_oid, Oid tgreloid)
                        free(prodesc->user_proname);
                        free(prodesc->internal_proname);
                        free(prodesc);
+                       UTF_BEGIN;
                        elog(ERROR, "could not create internal procedure \"%s\": %s",
-                                internal_proname, interp->result);
+                                internal_proname, UTF_U2E(Tcl_GetStringResult(interp)));
+                       UTF_END;
                }
 
                /************************************************************
@@ -1349,8 +1378,7 @@ pltcl_elog(ClientData cdata, Tcl_Interp *interp,
 
        if (argc != 3)
        {
-               Tcl_SetResult(interp, "syntax error - 'elog level msg'",
-                                         TCL_VOLATILE);
+               Tcl_SetResult(interp, "syntax error - 'elog level msg'", TCL_STATIC);
                return TCL_ERROR;
        }
 
@@ -1375,11 +1403,26 @@ pltcl_elog(ClientData cdata, Tcl_Interp *interp,
                return TCL_ERROR;
        }
 
-       /************************************************************
-        * If elog() throws an error, catch it and return the error to the
-        * Tcl interpreter.  Note we are assuming that elog() can't have any
+       if (level == ERROR)
+       {
+               /*
+                * We just pass the error back to Tcl.  If it's not caught,
+                * it'll eventually get converted to a PG error when we reach
+                * the call handler.
+                */
+               Tcl_SetResult(interp, (char *) argv[2], TCL_VOLATILE);
+               return TCL_ERROR;
+       }
+
+       /*
+        * For non-error messages, just pass 'em to elog().  We do not expect
+        * that this will fail, but just on the off chance it does, report the
+        * error back to Tcl.  Note we are assuming that elog() can't have any
         * internal failures that are so bad as to require a transaction abort.
-        ************************************************************/
+        *
+        * This path is also used for FATAL errors, which aren't going to come
+        * back to us at all.
+        */
        oldcontext = CurrentMemoryContext;
        PG_TRY();
        {
@@ -1397,7 +1440,9 @@ pltcl_elog(ClientData cdata, Tcl_Interp *interp,
                FlushErrorState();
 
                /* Pass the error message to Tcl */
-               Tcl_SetResult(interp, edata->message, TCL_VOLATILE);
+               UTF_BEGIN;
+               Tcl_SetResult(interp, UTF_E2U(edata->message), TCL_VOLATILE);
+               UTF_END;
                FreeErrorData(edata);
 
                return TCL_ERROR;
@@ -1425,7 +1470,7 @@ pltcl_quote(ClientData cdata, Tcl_Interp *interp,
         ************************************************************/
        if (argc != 2)
        {
-               Tcl_SetResult(interp, "syntax error - 'quote string'", TCL_VOLATILE);
+               Tcl_SetResult(interp, "syntax error - 'quote string'", TCL_STATIC);
                return TCL_ERROR;
        }
 
@@ -1477,7 +1522,8 @@ pltcl_argisnull(ClientData cdata, Tcl_Interp *interp,
         ************************************************************/
        if (argc != 2)
        {
-               Tcl_SetResult(interp, "syntax error - 'argisnull argno'", TCL_VOLATILE);
+               Tcl_SetResult(interp, "syntax error - 'argisnull argno'",
+                                         TCL_STATIC);
                return TCL_ERROR;
        }
 
@@ -1487,7 +1533,7 @@ pltcl_argisnull(ClientData cdata, Tcl_Interp *interp,
        if (fcinfo == NULL)
        {
                Tcl_SetResult(interp, "argisnull cannot be used in triggers",
-                                         TCL_VOLATILE);
+                                         TCL_STATIC);
                return TCL_ERROR;
        }
 
@@ -1503,7 +1549,7 @@ pltcl_argisnull(ClientData cdata, Tcl_Interp *interp,
        argno--;
        if (argno < 0 || argno >= fcinfo->nargs)
        {
-               Tcl_SetResult(interp, "argno out of range", TCL_VOLATILE);
+               Tcl_SetResult(interp, "argno out of range", TCL_STATIC);
                return TCL_ERROR;
        }
 
@@ -1511,9 +1557,9 @@ pltcl_argisnull(ClientData cdata, Tcl_Interp *interp,
         * Get the requested NULL state
         ************************************************************/
        if (PG_ARGISNULL(argno))
-               Tcl_SetResult(interp, "1", TCL_VOLATILE);
+               Tcl_SetResult(interp, "1", TCL_STATIC);
        else
-               Tcl_SetResult(interp, "0", TCL_VOLATILE);
+               Tcl_SetResult(interp, "0", TCL_STATIC);
 
        return TCL_OK;
 }
@@ -1533,7 +1579,7 @@ pltcl_returnnull(ClientData cdata, Tcl_Interp *interp,
         ************************************************************/
        if (argc != 1)
        {
-               Tcl_SetResult(interp, "syntax error - 'return_null'", TCL_VOLATILE);
+               Tcl_SetResult(interp, "syntax error - 'return_null'", TCL_STATIC);
                return TCL_ERROR;
        }
 
@@ -1543,7 +1589,7 @@ pltcl_returnnull(ClientData cdata, Tcl_Interp *interp,
        if (fcinfo == NULL)
        {
                Tcl_SetResult(interp, "return_null cannot be used in triggers",
-                                         TCL_VOLATILE);
+                                         TCL_STATIC);
                return TCL_ERROR;
        }
 
@@ -1629,7 +1675,9 @@ pltcl_subtrans_abort(Tcl_Interp *interp,
        SPI_restore_connection();
 
        /* Pass the error message to Tcl */
-       Tcl_SetResult(interp, edata->message, TCL_VOLATILE);
+       UTF_BEGIN;
+       Tcl_SetResult(interp, UTF_E2U(edata->message), TCL_VOLATILE);
+       UTF_END;
        FreeErrorData(edata);
 }
 
@@ -1661,7 +1709,7 @@ pltcl_SPI_execute(ClientData cdata, Tcl_Interp *interp,
         ************************************************************/
        if (argc < 2)
        {
-               Tcl_SetResult(interp, usage, TCL_VOLATILE);
+               Tcl_SetResult(interp, usage, TCL_STATIC);
                return TCL_ERROR;
        }
 
@@ -1672,7 +1720,7 @@ pltcl_SPI_execute(ClientData cdata, Tcl_Interp *interp,
                {
                        if (++i >= argc)
                        {
-                               Tcl_SetResult(interp, usage, TCL_VOLATILE);
+                               Tcl_SetResult(interp, usage, TCL_STATIC);
                                return TCL_ERROR;
                        }
                        arrayname = argv[i++];
@@ -1683,7 +1731,7 @@ pltcl_SPI_execute(ClientData cdata, Tcl_Interp *interp,
                {
                        if (++i >= argc)
                        {
-                               Tcl_SetResult(interp, usage, TCL_VOLATILE);
+                               Tcl_SetResult(interp, usage, TCL_STATIC);
                                return TCL_ERROR;
                        }
                        if (Tcl_GetInt(interp, argv[i++], &count) != TCL_OK)
@@ -1697,7 +1745,7 @@ pltcl_SPI_execute(ClientData cdata, Tcl_Interp *interp,
        query_idx = i;
        if (query_idx >= argc || query_idx + 2 < argc)
        {
-               Tcl_SetResult(interp, usage, TCL_VOLATILE);
+               Tcl_SetResult(interp, usage, TCL_STATIC);
                return TCL_ERROR;
        }
        if (query_idx + 1 < argc)
@@ -1769,7 +1817,7 @@ pltcl_process_SPI_result(Tcl_Interp *interp,
                case SPI_OK_UTILITY:
                        if (tuptable == NULL)
                        {
-                               Tcl_SetResult(interp, "0", TCL_VOLATILE);
+                               Tcl_SetResult(interp, "0", TCL_STATIC);
                                break;
                        }
                        /* FALL THRU for utility returning tuples */
@@ -1873,7 +1921,7 @@ pltcl_SPI_prepare(ClientData cdata, Tcl_Interp *interp,
        if (argc != 3)
        {
                Tcl_SetResult(interp, "syntax error - 'SPI_prepare query argtypes'",
-                                         TCL_VOLATILE);
+                                         TCL_STATIC);
                return TCL_ERROR;
        }
 
@@ -1974,6 +2022,7 @@ pltcl_SPI_prepare(ClientData cdata, Tcl_Interp *interp,
 
        ckfree((char *) args);
 
+       /* qname is ASCII, so no need for encoding conversion */
        Tcl_SetResult(interp, qdesc->qname, TCL_VOLATILE);
        return TCL_OK;
 }
@@ -2017,7 +2066,7 @@ pltcl_SPI_execute_plan(ClientData cdata, Tcl_Interp *interp,
                {
                        if (++i >= argc)
                        {
-                               Tcl_SetResult(interp, usage, TCL_VOLATILE);
+                               Tcl_SetResult(interp, usage, TCL_STATIC);
                                return TCL_ERROR;
                        }
                        arrayname = argv[i++];
@@ -2027,7 +2076,7 @@ pltcl_SPI_execute_plan(ClientData cdata, Tcl_Interp *interp,
                {
                        if (++i >= argc)
                        {
-                               Tcl_SetResult(interp, usage, TCL_VOLATILE);
+                               Tcl_SetResult(interp, usage, TCL_STATIC);
                                return TCL_ERROR;
                        }
                        nulls = argv[i++];
@@ -2037,7 +2086,7 @@ pltcl_SPI_execute_plan(ClientData cdata, Tcl_Interp *interp,
                {
                        if (++i >= argc)
                        {
-                               Tcl_SetResult(interp, usage, TCL_VOLATILE);
+                               Tcl_SetResult(interp, usage, TCL_STATIC);
                                return TCL_ERROR;
                        }
                        if (Tcl_GetInt(interp, argv[i++], &count) != TCL_OK)
@@ -2053,7 +2102,7 @@ pltcl_SPI_execute_plan(ClientData cdata, Tcl_Interp *interp,
         ************************************************************/
        if (i >= argc)
        {
-               Tcl_SetResult(interp, usage, TCL_VOLATILE);
+               Tcl_SetResult(interp, usage, TCL_STATIC);
                return TCL_ERROR;
        }
 
@@ -2080,7 +2129,7 @@ pltcl_SPI_execute_plan(ClientData cdata, Tcl_Interp *interp,
                {
                        Tcl_SetResult(interp,
                                           "length of nulls string doesn't match # of arguments",
-                                                 TCL_VOLATILE);
+                                                 TCL_STATIC);
                        return TCL_ERROR;
                }
        }
@@ -2093,7 +2142,7 @@ pltcl_SPI_execute_plan(ClientData cdata, Tcl_Interp *interp,
        {
                if (i >= argc)
                {
-                       Tcl_SetResult(interp, "missing argument list", TCL_VOLATILE);
+                       Tcl_SetResult(interp, "missing argument list", TCL_STATIC);
                        return TCL_ERROR;
                }
 
@@ -2110,7 +2159,7 @@ pltcl_SPI_execute_plan(ClientData cdata, Tcl_Interp *interp,
                {
                        Tcl_SetResult(interp,
                           "argument list length doesn't match # of arguments for query",
-                                                 TCL_VOLATILE);
+                                                 TCL_STATIC);
                        ckfree((char *) callargs);
                        return TCL_ERROR;
                }
@@ -2126,7 +2175,7 @@ pltcl_SPI_execute_plan(ClientData cdata, Tcl_Interp *interp,
 
        if (i != argc)
        {
-               Tcl_SetResult(interp, usage, TCL_VOLATILE);
+               Tcl_SetResult(interp, usage, TCL_STATIC);
                return TCL_ERROR;
        }