[Ovmsdev] Use of deallocated memory in a bunch of places!?

[Michael Balzer]

Michael,

oh, the dreadful c_str() trap once again… nice find.

The deallocated heap buffer *can* have been reallocated easily, we're 
running on a preemptive OS and on two CPU cores.

IOW, all of these need to be fixed. Sure there are only 8 of them?

On your is_empty_metric() utility: may be I miss something, but why 
don't we simply use the metric's IsDefined() method?

Regards,
Michael


Am 02.10.22 um 13:37 schrieb Michael Geddes:
> Hi all,
>
> I noticed some behavior on the *tpms* command I'd copied from the 
> Kia/Kona code, which sent me down a small rabbit hole.
> What I was seeing was that the temperature was repeated instead of 
> seeing the pressure and temperature.
>
> Even in vehicle.cpp, we can see code like this:
>
> const char* range_est = 
> StdMetrics.ms_v_bat_range_est->AsUnitString("-", rangeUnit, 0).c_str();
>   if (*range_est != '-')
>     writer->printf("Est. range: %s\n", range_est);
>
> My C++ is a bit rusty, however I believe that the 'const char*' won't 
> hold the temporary std::string object returned by 'AsUnitString'.  To 
> do that, I believe we need to assign to a reference (which I know will 
> work).  The problem is that the original code will mostly work 
> (especially in cases like the above), as the deallocated heap memory 
> won't have been reallocated.
>
>   const std::string& range_est = 
> StdMetrics.ms_v_bat_range_est->AsUnitString("-", rangeUnit, 0);
>   if (!is_empty_metric(range_est))
>     writer->printf("Est. range: %s\n", range_est.c_str());
>
> Where I've defined in vehicle.h the following:
> inline bool is_empty_metric(const std::string &measure)
> {
>   return (measure == "") || (measure[0] == '-');
> }
>
> Will the above work functionally?  Would it be better to be:
>
> return (measure =="") || (measure == "-")
>
> This occurs in 8 files (outside my new Ioniq 5 files) that I have noted.
>
> I would make a separate commit for this and do a pull request for it,
>
> //.ichael
>
>
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-- 
Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
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