MySQL Bugs: #69700: MYSQL_SERVER_VERSION value missmatch with mysql-connector-c but not in server

Bug #69700	MYSQL_SERVER_VERSION value missmatch with mysql-connector-c but not in server
Submitted:	9 Jul 2013 16:48	Modified:	11 Apr 2014 13:38
Reporter:	Ian Flynn	Email Updates:
Status:	Closed	Impact on me:	None
Category:	Connector / C	Severity:	S3 (Non-critical)
Version:	6.1.0	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
In mysql-connector-c-6.1.0-winx64 include/mysql_version.h line 13:

#define MYSQL_SERVER_VERSION       "5.7.2-m12"
calling mysql_get_client_info() on the included dll yields: 6.1.0

In mysql-5.6.12-winx64 include/mysql_version.h line 13:
#define MYSQL_SERVER_VERSION		"5.6.12"

calling mysql_get_client_info() on the included dll yields:  5.6.12

In other words, in mysql's include files, MYSQL_SERVER_VERSION matches the return of mysql_get_client_info() on the dll from the same distribution. In the mysql-connector-c library, these values do not match.

How to repeat:
Build from referenced codebases, call mysql_get_client_info() on supplied dlls.

Suggested fix:
Is this expected behavior? If we are linking against either mysql or the connector library, how can we ensure that the dll we are using matches? Should we be checking a different variable other than MYSQL_SERVER_VERSION, or should we be calling a different funciton on the dll, other than mysql_get_client_info()?

I note that in the connector library LIBMYSQL_VERSION matches what is returned from mysql_get_client_info(), but is this the recommended value to use? Is there a value that exists in both the connector library and the server code that can be used in both situations?

what is the reason to have a separate version of mysql-connector-c that is not the same as the client/server version on which it is based?

Thank you for the bug report.

c:\tmp>bug69700a.exe
Client Info: 5.6.12
Done

c:\tmp>bug69700a.exe
Client Info: 6.1.0
Done

c:\tmp>type c:\mysql-connector-c-6.1.0-winx64\include\mysql_version.h | findstr MYSQL_SERVER_VERSION
#define MYSQL_SERVER_VERSION       "5.7.2-m12"

c:\tmp>

Posted by developer:
 
Refined problem description
===========================
It is not possible to write portable code which checks version of
libmysql at runtime that would work with both libmysql from server
distribution and with Connector/C.

If using server's version of the library the check might look as follows:

  if (mysql_get_client_version() < MYSQL_VERSION_ID)
  {
     // Error: we use too old version of libmysql
  }

This code will not work with Connector/C for which
mysql_get_client_version() returns something like 6XXYY and
MYSQL_VERSION_ID is 506ZZ. In Connector/C one needs to use the following
check instead:

  if (mysql_get_client_version() < LIBMYSQL_VERSION_ID)
  {
     // Error: we use too old version of libmysql
  }

But this code will not build with server sources because there
LIBMYSQL_VERSION_ID is not defined. Currently there is no portable way
to write such a check so that the code would compile and work correctly
both with server sources and with c/C.

Proposed solution
=================
Introduce LIBMYSQL_VERSION_ID constant to server sources. Here it will
be equal to MYSQL_VERSION_ID. Thus the second variant of version check
would work for both server and c/C.

Note: we would still have a problem that code which contains such checks
and is built with c/C sources will refuse to work with server's version
of libmysql - only c/C version will pass the check because c/C's version
number is higher than server version number.

Noted in MySQL 5.7.4 and Connector/C 6.1.3 changelogs.

The mysql_version.h file defines two new macros, LIBMYSQL_VERSION and
LIBMYSQL_VERSION_ID, that indicate the string and numeric forms of
the client library version.

* In the client library included with MySQL Server distributions, these
  macros have the same values as MYSQL_SERVER_VERSION and
  MYSQL_VERSION_ID. For example, in MySQL 5.7.4, MYSQL_SERVER_VERSION
  and LIBMYSQL_VERSION are "5.7.4-m14", and MYSQL_VERSION_ID and
  LIBMYSQL_VERSION_ID are 50704.

* In the client library included with Connector/C distributions,
  MYSQL_SERVER_VERSION and MYSQL_VERSION_ID have the values of the
  MySQL version on which the Connector/C distribution is based, whereas
  LIBMYSQL_VERSION and LIBMYSQL_VERSION_ID indicate the Connector/C
  version. For example, Connector/C 6.1.3 is based on MySQL 5.7.4, so
  MYSQL_SERVER_VERSION and MYSQL_VERSION_ID have values of "5.7.4-m14"
  and 50704, whereas LIBMYSQL_VERSION and LIBMYSQL_VERSION_ID have
  values of "6.1.3" and 60103.

In addition, the mysql_get_client_info() and
mysql_get_client_version() C API functions in the client library now
return values that reflect the type of distribution that provides the
client library:

* In MySQL distributions, mysql_get_client_info() returns
  MYSQL_SERVER_VERSION and mysql_get_client_version() returns
  MYSQL_VERSION_ID. This is the same as before.

* In Connector/C distributions, mysql_get_client_info() returns
  LIBMYSQL_VERSION and mysql_get_client_version() returns
  LIBMYSQL_VERSION_ID. Previously, these functions returned the MySQL
  version, the same as in MySQL distributions.