I have written a simple UDF to get the time as a string from a timestamp, returning '00:00:00' if no valid input was given. There seems to be a problem when calling the UDF, the server crashes. This is the only UDF I have ever created that allocates memory and returns said memory to the database, so I am figuring either the declaration of the UDF is wrong or the C code itself is wrong. Here is what I have:

DECLARE EXTERNAL FUNCTION TRUNK_TIMESTAMP_TO_TIME
DATE
RETURNS CSTRING(8) FREE_IT
ENTRY_POINT 'fn_timestr' MODULE_NAME 'my_udf';

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char* EXPORT fn_timestr (ARG(ISC_TIMESTAMP*, ts))
ARGLIST(struct ISC_TIMESTAMP* ts)
{
short bufByteSize = sizeof(char) * 9;
char *datebuf = (char *)malloc(bufByteSize);

struct tm tm_src;

if(ts && (ts->timestamp_date || ts->timestamp_time))
{
isc_decode_timestamp(ts, &tm_src);
strftime(datebuf, bufByteSize, "%H:%M:%S", &tm_src);
}
else
{
strcpy(datebuf, "00:00:00");
}

return datebuf;
}