MySQL 5.4 Reference Manual :: 20 Connectors and APIs :: 20.9 MySQL C API :: 20.9.3 C API Function Descriptions :: 20.9.3.25 mysql_free_result()
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- 20.9.3 C API Function Descriptions
- 20.9.3.1 mysql_affected_rows()
- 20.9.3.2 mysql_autocommit()
- 20.9.3.3 mysql_change_user()
- 20.9.3.4 mysql_character_set_name()
- 20.9.3.5 mysql_close()
- 20.9.3.6 mysql_commit()
- 20.9.3.7 mysql_connect()
- 20.9.3.8 mysql_create_db()
- 20.9.3.9 mysql_data_seek()
- 20.9.3.10 mysql_debug()
- 20.9.3.11 mysql_drop_db()
- 20.9.3.12 mysql_dump_debug_info()
- 20.9.3.13 mysql_eof()
- 20.9.3.14 mysql_errno()
- 20.9.3.15 mysql_error()
- 20.9.3.16 mysql_escape_string()
- 20.9.3.17 mysql_fetch_field()
- 20.9.3.18 mysql_fetch_field_direct()
- 20.9.3.19 mysql_fetch_fields()
- 20.9.3.20 mysql_fetch_lengths()
- 20.9.3.21 mysql_fetch_row()
- 20.9.3.22 mysql_field_count()
- 20.9.3.23 mysql_field_seek()
- 20.9.3.24 mysql_field_tell()
- 20.9.3.25 mysql_free_result()
- 20.9.3.26 mysql_get_character_set_info()
- 20.9.3.27 mysql_get_client_info()
- 20.9.3.28 mysql_get_client_version()
- 20.9.3.29 mysql_get_host_info()
- 20.9.3.30 mysql_get_proto_info()
- 20.9.3.31 mysql_get_server_info()
- 20.9.3.32 mysql_get_server_version()
- 20.9.3.33 mysql_get_ssl_cipher()
- 20.9.3.34 mysql_hex_string()
- 20.9.3.35 mysql_info()
- 20.9.3.36 mysql_init()
- 20.9.3.37 mysql_insert_id()
- 20.9.3.38 mysql_kill()
- 20.9.3.39 mysql_library_end()
- 20.9.3.40 mysql_library_init()
- 20.9.3.41 mysql_list_dbs()
- 20.9.3.42 mysql_list_fields()
- 20.9.3.43 mysql_list_processes()
- 20.9.3.44 mysql_list_tables()
- 20.9.3.45 mysql_more_results()
- 20.9.3.46 mysql_next_result()
- 20.9.3.47 mysql_num_fields()
- 20.9.3.48 mysql_num_rows()
- 20.9.3.49 mysql_options()
- 20.9.3.50 mysql_ping()
- 20.9.3.51 mysql_query()
- 20.9.3.52 mysql_real_connect()
- 20.9.3.53 mysql_real_escape_string()
- 20.9.3.54 mysql_real_query()
- 20.9.3.55 mysql_refresh()
- 20.9.3.56 mysql_reload()
- 20.9.3.57 mysql_rollback()
- 20.9.3.58 mysql_row_seek()
- 20.9.3.59 mysql_row_tell()
- 20.9.3.60 mysql_select_db()
- 20.9.3.61 mysql_set_character_set()
- 20.9.3.62 mysql_set_local_infile_default()
- 20.9.3.63 mysql_set_local_infile_handler()
- 20.9.3.64 mysql_set_server_option()
- 20.9.3.65 mysql_shutdown()
- 20.9.3.66 mysql_sqlstate()
- 20.9.3.67 mysql_ssl_set()
- 20.9.3.68 mysql_stat()
- 20.9.3.69 mysql_store_result()
- 20.9.3.70 mysql_thread_id()
- 20.9.3.71 mysql_use_result()
- 20.9.3.72 mysql_warning_count()
void mysql_free_result(MYSQL_RES *result)
Description
Frees the memory allocated for a result set by
mysql_store_result(),
mysql_use_result(),
mysql_list_dbs(), and so forth.
When you are done with a result set, you must free the memory it
uses by calling
mysql_free_result().
Do not attempt to access a result set after freeing it.
Return Values
None.
Errors
None.
User Comments
mysql_free_result() free the MYSQL_RES, but it didn't set result to NULL. When we want to check result in other code, we can set result as default NULL where after call mysql_free_result(), and Set result as default NULL before store it.
Example:
MYSQL mysql;
MYSQL_RES *res;
MYSQL_ROW row;
res = NULL; // Set res as default NULL
mysql_init(&mysql);
mysql_real_connect(&mysql,"localhost","root","","test",0,NULL,0);
mysql_query(&mysql,"SELECT * FROM person WHERE no<\'10\'");
res = mysql_store_result(&mysql);
..... other code here.....
... maybe check res is NULL or not
.......
mysql_free_result(res);
res = NULL; // Set res as default NULL
....
mysql_close(&mysql);
////////////
// Notes:
If result is NULL, we call mysql_free_result(res) is ok.
If call mysql_free_result(res) more once, we can get an memory access error.
Example:(OK)
res = mysql_store_result(&mysql);
......
mysql_free_result(res); // call free result once
res = NULL;
....
mysql_free_result(res); // call free result more then once is ok, because we set res as default NULL when after call mysql_free_result()
Example:(BAD,ERROR)
res = mysql_store_result(&mysql);
......
mysql_free_result(res); // must call free result once
....
mysql_free_result(res); // call free result more then once is BAD, because res is unallocated now.
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