[m-rev.] Fwd: for review: fix obsolete tcl-tk code in extras/graphics/mercury_tcltk

[Julien Fischer]

Hi Fabrice,

On Thu, 6 Jan 2022, Fabrice Nicol wrote:

> Hi Julien,
>>  According the Tcl/Tk documentation TCL_DYANMIC is for when the memory
>>  referenced by the result field is allocated using the Tcl_Alloc()
>>  function.  (Memory allocated by Mercury's GC is definitely *not*
>>  allocated using this function.)
>>
>>  I think the safest approach here is to get the result string from
>>  Mercury, copy it into memory allocated using Tcl_Alloc() and then
>>  pass that to Tcl_SetResult().
>> 
> Ok, I hope the attached patch sets things straight if TCL_DYNAMIC is to be 
> preferred.

Just one question: why are you only copying the first 2047 bytes of
the string instead of copying the entire string?

> In the process, I added a missing foreign_enum pragma for Mercury type 
> 'tcl_status' (see commit message).

Thanks for that.  The Tcl/Tk binding predates the addition of
foreign_enum pragmas to the language.  The existing code just happened
to (nearly always) work because the values of the C constants matched
the representation Mercury uses for values of that type.

Julien.