On 01/06/2014 03:09 PM, Masterprojekt Naumann1 wrote:
I want to read an attribute value from a TupleTableSlot. When I try to convert an attribute of SQL type varchar from Datum* to char* with the help of the method TextDatumGetCString(...), sometimes there is a segmentation fault. The segmentation fault comes from the method TextDatumGetCString(...), which is defined in utils/builtins.h. Unfortunately, the fault is not always reproducible. I debugged the code and figured out that the value of result->tts_values[i] sometimes is random. It may be uninitialized memory. In other cases, the variable value is NULL. Then, I can just skip the conversion from Datum* to char*, so that there is no segmentation fault. I attached a patch with the code. The relevant line is: char *value = TextDatumGetCString(result->tts_values[i]); The SQL-Query is a simple "SELECT * from ..." on the TPC-H table customer. About every third execution leads to a segmentation fault.
Maybe the field 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.
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