Fix pl/tcl's handling of errors from Tcl_ListObjGetElements().
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
Branch
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REL_15_STABLE
Details
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https://git.postgresql.org/pg/commitdiff/89ef2aedae448cc51cd7bf7c81d56a08d1da7467
Modified Files
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src/pl/tcl/expected/pltcl_call.out | 8 ++++++++
src/pl/tcl/pltcl.c | 11 +++++++++--
src/pl/tcl/sql/pltcl_call.sql | 11 +++++++++++
3 files changed, 28 insertions(+), 2 deletions(-)