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Fix pl/tcl's handling of errors from Tcl_ListObjGetElements().

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In a procedure or function returning tuple, we use that function to
parse the Tcl script's result, which is supposed to be a Tcl list.
If it isn't, you get an error.  Commit 26abb50c4 incautiously
supposed that we could use throw_tcl_error() to report such an error.
That doesn't actually work, because low-level functions like
Tcl_ListObjGetElements() don't fill Tcl's errorInfo variable.
The result is either a null-pointer-dereference crash or emission
of misleading context information describing the previous Tcl error.

Back off to just reporting the interpreter's result string, and
improve throw_tcl_error()'s comment to explain when to use it.

Also, although the similar code in pltcl_trigger_handler() avoided
this mistake, it was using a fairly confusing wording of the
error message.  Improve that while we're here.

Per report from A. Kozhemyakin.  Back-patch to all supported
branches.

Erik Wienhold and Tom Lane

Discussion: https://postgr.es/m/6a2a1c40-2b2c-4a33-8b72-243c0766fcda@postgrespro.ru
This commit is contained in:
Tom Lane 2024-06-04 18:02:13 -04:00
parent 1d5c5ae8e5
commit dda633a039
3 changed files with 28 additions and 2 deletions
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8
src/pl/tcl/expected/pltcl_call.out
View File

@ -49,6 +49,14 @@ CALL test_proc6(2, 3, 4);
6 | 8
(1 row)
-- syntax error in result tuple
CREATE PROCEDURE test_proc10(INOUT a text)
LANGUAGE pltcl
AS $$
return [list a {$a + $a}])
$$;
CALL test_proc10('abc');
ERROR: could not parse function return value: list element in braces followed by ")" instead of space
DROP PROCEDURE test_proc1;
DROP PROCEDURE test_proc2;
DROP PROCEDURE test_proc3;

11
src/pl/tcl/pltcl.c
View File

@ -1022,7 +1022,10 @@ pltcl_func_handler(PG_FUNCTION_ARGS, pltcl_call_state *call_state,
/* Convert function result to tuple */
resultObj = Tcl_GetObjResult(interp);
if (Tcl_ListObjGetElements(interp, resultObj, &resultObjc, &resultObjv) == TCL_ERROR)
throw_tcl_error(interp, prodesc->user_proname);
ereport(ERROR,
(errcode(ERRCODE_EXTERNAL_ROUTINE_EXCEPTION),
errmsg("could not parse function return value: %s",
utf_u2e(Tcl_GetStringResult(interp)))));
tup = pltcl_build_tuple_result(interp, resultObjv, resultObjc,
call_state);
@ -1289,7 +1292,7 @@ pltcl_trigger_handler(PG_FUNCTION_ARGS, pltcl_call_state *call_state,
&result_Objc, &result_Objv) != TCL_OK)
ereport(ERROR,
(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
errmsg("could not split return value from trigger: %s",
errmsg("could not parse trigger return value: %s",
utf_u2e(Tcl_GetStringResult(interp)))));
/* Convert function result to tuple */
@ -1352,6 +1355,10 @@ pltcl_event_trigger_handler(PG_FUNCTION_ARGS, pltcl_call_state *call_state,
/**********************************************************************
* throw_tcl_error - ereport an error returned from the Tcl interpreter
*
* Caution: use this only to report errors returned by Tcl_EvalObjEx() or
* other variants of Tcl_Eval(). Other functions may not fill "errorInfo",
* so it could be unset or even contain details from some previous error.
**********************************************************************/
static void
throw_tcl_error(Tcl_Interp *interp, const char *proname)

11
src/pl/tcl/sql/pltcl_call.sql
View File

@ -52,6 +52,17 @@ $$;
CALL test_proc6(2, 3, 4);
-- syntax error in result tuple
CREATE PROCEDURE test_proc10(INOUT a text)
LANGUAGE pltcl
AS $$
return [list a {$a + $a}])
$$;
CALL test_proc10('abc');
DROP PROCEDURE test_proc1;
DROP PROCEDURE test_proc2;
DROP PROCEDURE test_proc3;