corrupt heap at MySQL_Connection destructor

[pabloandresm]

The MySQL_Connection destructor performs:
if (server_version) free(server_version);

...but....

the variable "server_version" is not initialized to NULL in the MySQL_Packet constructor.

The variable "server_version" must be initialized to NULL in the MySQL_Packet constructor, exactly as the "buffer" is (see MySQL_Generic_Packet_Impl.h line 74)

This ends up, in some cases:
CORRUPT HEAP: Bad head at 0x3fff2344. Expected 0xabba1234 got 0x3ffe4364
assert failed: multi_heap_free multi_heap_poisoning.c:253 (head != NULL)

[pabloandresm]

Hello.

That is not the only problem. I still receive "CORRUPT HEAP: Bad head at 0x3fff2334. Expected 0xabba1234 got 0x3ffe4364", "assert failed: multi_heap_free multi_heap_poisoning.c:253 (head != NULL)"

Let me investigate further and I'll keep you informed on my research.

Just one question, why do you free(server_version) in the destructor of the MySQL_Connection? I think it should be done in the destructor of MySQL_Packet, same way the "free(buffer)", as both variables are of that class and malloc on that class.

[pabloandresm]

FOUND IT!

I suggest 3 things to fix this:

1. initialize "server_version=NULL;" at MySQL_Packet constructor, exactly as the "buffer" is.
2. free server version the same way "buffer" is, in the destructor of MySQL_Packet, and not destructor of MySQL_Connection
3. the two connect() in MySQL_Connection do "free(server_version)", but you forget to do "server_version=NULL;" afterwards, so the destructor will try to free it again, triggering the segmentation fault.

two times you can find this in your code:
if (server_version)
free(server_version); // don't need it anymore

and it should be:
if (server_version) {
free(server_version); // don't need it anymore
server_version=NULL;
}

hope this helps. In any case the segmentation fault dissappears and everything works correctly after those 4 changes (the last one is located in two places)

[khoih-prog]

Hi @pabloandresm

Thanks for spending time to investigate and propose the fix.
I've been actually so busy with other libraries (100+) and could spend only a short time yesterday with this library, after so long time. Therefore, a sloppy job.

Will spend some more time to have a more detailed look. I'd appreciate it if you can help by creating a PR to save me some time. If not, I'll do it anyway.

Regards,

[pabloandresm]

pleasure to help.

I've tested these 3 modifications I am suggestion, as well as the other bug fix I've created, and everything works fine.

Regards,

[khoih-prog]

Close #19 via PR #21