Re: (ITS#7899) Segfault after transaction comitted

[hyc@symas.com]

zxcvbn4038@gmail.com wrote:
> Full_Name: CJS
> Version: 0.9.14
> OS: MacOS
> URL: ftp://ftp.openldap.org/incoming/
> Submission from: (NULL) (66.6.34.253)
>
>
> In the code below if you comment out the second mdb_txn_begin as below then the
> mdb_get will segfault. I finally figured out I need to open a new transaction,
> but it may have been more appropriate to return an invalid parameter error then
> to segfault.

Works as designed and as documented.
http://symas.com/mdb/doc/group__mdb.html#ga846fbd6f46105617ac9f4d76476f6597

Segfault == programmer error. That's perfectly appropriate.

Closing this ITS.

> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> #include <lmdb.h>
>
> #define E(expr) CHECK((rc = (expr)) == MDB_SUCCESS, #expr)
> #define RES(err, expr) ((rc = expr) == (err) || (CHECK(!rc, #expr), 0))
> #define CHECK(test, msg) ((test) ? (void)0 : ((void)fprintf(stderr, \
>          "%s:%d: %s: %s\n", __FILE__, __LINE__, msg, mdb_strerror(rc)),
> abort()))
>
> int main() {
>    int rc;
>    MDB_env *env;
>    MDB_txn *txn;
>    MDB_dbi dbi;
>    MDB_val key, data;
>    unsigned long kval = 0xdeadbeef;
>    unsigned long dval = 0xbeefdead;
>
>    E(mdb_env_create(&env));
>    E(mdb_env_set_mapsize(env, 10485760));
>    E(mdb_env_set_maxdbs(env, 4));
>    E(mdb_env_open(env, "./lmdbtestdb", MDB_NOSYNC, 0664));
>    E(mdb_txn_begin(env, NULL, 0, &txn));
>    E(mdb_open(txn, NULL, 0, &dbi));
>
>    key.mv_size = sizeof(kval);
>    key.mv_data = &kval;
>    data.mv_size = sizeof(dval);
>    data.mv_data = &dval;
>
>    printf("kval=0x%016lx, dval=0x%016lx\n", kval, dval);
>
>    RES(MDB_KEYEXIST, mdb_put(txn, dbi, &key, &data, MDB_NOOVERWRITE));
>
>    E(mdb_txn_commit(txn));
>    //E(mdb_txn_begin(env, NULL, 0, &txn));
>
>    rc = mdb_get(txn, dbi, &key, &data);
>    printf("rc=%i (%s)\n", rc, mdb_strerror(rc));
>
>    printf("Result should be 0xbeefdead: 0x%016lx (%lu)\n", *(unsigned long
> *)data.mv_data, data.mv_size) ;
>
>    //E(mdb_txn_commit(txn));
>    mdb_close(env, dbi);
>    mdb_env_close(env);
>
>    return(1);
> }
>
>


-- 
   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
   Chief Architect, OpenLDAP  http://www.openldap.org/project/