Segmenation fault

Question

Hello,
db->put( data = DB_DBT_USERMEM | DB_DBT_PARTIAL ) causes a segfault.
Thanks
Markus
The backtrace (freeing memory - strange):
/lib/tls/i686/cmov/libc.so.6 [0xb788f9f4]
/lib/tls/i686/cmov/libc.so.6(cfree+0x90) [0xb78934f0]
/usr/local/lib/libdb-4.7.so(__os_free+0x39) [0xb7ee01e9]
/usr/local/lib/libdb-4.7.so(__lock_detect+0x846) [0xb7e6d3f6]
/usr/local/lib/libdb-4.7.so(__lock_vec+0xbdc) [0xb7e6c5dc]
/usr/local/lib/libdb-4.7.so(__db_lget+0x278) [0xb7e952f8]
/usr/local/lib/libdb-4.7.so(__bam_search+0x797) [0xb7dfc7e7]
/usr/local/lib/libdb-4.7.so [0xb7dea994]
/usr/local/lib/libdb-4.7.so [0xb7decc75]
/usr/local/lib/libdb-4.7.so(__dbc_get+0x1e5) [0xb7e86e05]
/usr/local/lib/libdb-4.7.so(__db_get+0xb1) [0xb7e91391]
/usr/local/lib/libdb-4.7.so(__db_get_pp+0x20a) [0xb7e9276a]
Pseudo-code:
DBT data;
memset( &data, 0, sizeof(DBT) );
data.data = NULL;
data.size = 0;
data.ulen = 0;
data.flags = 0;
table->get( table, transaction, &key, &data, DB_RMW );
if( status != 0 )
return ;
Create a new "data" value
Compare bytes so that only the new area (likely bigger) is written back
Write back partial data:
int value_old_offsetstart = index where changes started
int value_old_offsetstart = index where changes ended
int value_new_offsetstart = index where changes started
int value_new_offsetstart = index where changes ended
data.data = (void*)(value_new + value_new_offsetstart);
data.size = value_new_offsetend - value_new_offsetstart;
data.ulen = 0;
data.dlen = value_old_offsetend - value_old_offsetstart;
data.doff = value_old_offsetstart;
data.flags = DB_DBT_USERMEM | DB_DBT_PARTIAL;
table->put( table, transaction, &key, &data, 0 );

Answer 1

Hello. From the stack trace you provided, the error is caused by the DB->get() call, not the DB->put().
Could you post a small, stand alone program that replicates this segfault?
Thanks,
Ben Schmeckpeper