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MariaDB server is a community developed fork of MySQL server. Started by core members of the original MySQL team, MariaDB actively works with outside developers to deliver the most featureful, stable, and sanely licensed open SQL server in the industry.
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The C optimizer may decide that data access operations through pointer of different type are not related to the original data (strict aliasing). This is what happens in fetch_long_with_conversion(), when called as part of mysql_stmt_fetch() : it tries to check for truncation errors by first storing float (and other types of data) into a char * buffer and then accesses them through a float pointer. This is done to prevent the effects of excess precision when using FPU registers. However the doublestore() macro converts a double pointer to an union pointer. This violates the strict aliasing rule. Fixed by making the intermediary variables volatile ( to not re-introduce the excess precision bug) and using the intermediary value instead of the char * buffer. Note that there can be loss of precision for both signed and unsigned 64 bit integers converted to double and back, so the check must stay there (even for compatibility reasons). Based on the excellent analysis in bug 28400. libmysql/libmysql.c: Bug #27383: avoid pointer aliasing problems while not re-violating the Intel FPU gcc bug. |
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| README | ||
This is a release of MySQL, a dual-license SQL database server. MySQL is brought to you by the MySQL team at MySQL AB. License information can be found in these files: - For GPL (free) distributions, see the COPYING file and the EXCEPTIONS-CLIENT file. - For commercial distributions, see the LICENSE.mysql file. For further information about MySQL or additional documentation, see: - The latest information about MySQL: http://www.mysql.com - The current MySQL documentation: http://dev.mysql.com/doc Some manual sections of special interest: - If you are migrating from an older version of MySQL, please read the "Upgrading from..." section first! - To see what MySQL can do, take a look at the features section. - For installation instructions, see the Installing and Upgrading chapter. - For the new features/bugfix history, see the Change History appendix. - For the currently known bugs/misfeatures (known errors) see the Problems and Common Errors appendix. - For a list of developers and other contributors, see the Credits appendix. A local copy of the MySQL Reference Manual can be found in the Docs directory in GNU Info format. You can also browse the manual online or download it in any of several formats at the URL given earlier in this file. ************************************************************ IMPORTANT: Bug or error reports should be sent to http://bugs.mysql.com.