Re: Convert Datum* to char*

<div dir="ltr">Yes, in some cases, Datum is 0, which I test before conversion. Additionally, I looked at tts_isnull but
itdoes not prevent the segmentation fault in some cases. The problem is. that sometimes the value is random, but I
don'tknow why and how I can detect that case.<br /></div><div class="gmail_extra"><br /><br /><div
class="gmail_quote">2014/1/6Heikki Linnakangas <span dir="ltr"><<a href="mailto:hlinnakangas@vmware.com"
target="_blank">hlinnakangas@vmware.com</a>></span><br/><blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px#ccc solid;padding-left:1ex"><div class="im">On 01/06/2014 03:09 PM, Masterprojekt Naumann1
wrote:<br/><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> I
wantto read an attribute value from a TupleTableSlot. When I try to<br /> convert an attribute of SQL type varchar from
Datum*to char* with the help<br /> of the method TextDatumGetCString(...), sometimes there is a segmentation<br />
fault.The segmentation fault comes from the method<br /> TextDatumGetCString(...), which is defined in
utils/builtins.h.<br/> Unfortunately, the fault is not always reproducible. I debugged the code<br /> and figured out
thatthe value of result->tts_values[i] sometimes is<br /> random. It may be uninitialized memory. In other cases,
thevariable value<br /> is NULL. Then, I can just skip the conversion from Datum* to char*, so that<br /> there is no
segmentationfault. I attached a patch with the code. The<br /> relevant line is:<br /> char *value =
TextDatumGetCString(result-><u></u>tts_values[i]);<br/> The SQL-Query is a simple "SELECT * from ..." on the TPC-H
tablecustomer.<br /> About every third execution leads to a segmentation fault.<br /></blockquote><br /></div> Maybe
thefield is NULL? By convention, we normally set the Datum to 0 on an SQL NULL, but you're supposed to check tts_isnull
first,and ignore tts_values[x] when tts_isnull[x] is true.<span class="HOEnZb"><font color="#888888"><br /><br /> -
Heikki<br/></font></span></blockquote></div><br /></div>