strict aliasing violations.
Essentially, the problem is that large parts of the server were
developed in simpler times (last decades, pre C99 standard) when
strict aliasing and compilers supporting such optimizations were
rare to non-existent. Thus, when compiling the server with a modern
compiler that uses strict aliasing rules to perform optimizations,
there are several places in the code that might trigger undefined
behavior.
As evinced by some recent bugs, GCC does a somewhat good of job
misoptimizing such code, but on the other hand also gives warnings
about suspicious code. One problem is that the warnings aren't
always accurate, yet we can't afford to just shut them off as we
might miss real cases. False-positive cases are aggravated mostly
by casts that are likely to trigger undefined behavior.
The solution is to start a cleanup process focused on fixing and
reducing the amount of strict-aliasing related warnings produced
by GCC and others compilers. A good deal of noise reduction can
be achieved by just removing useless casts that are product of
historical cruft and are likely to trigger undefined behavior if
dereferenced.
The problem was that mysqltest could attempt to execute a
SHOW WARNINGS statement through a connection that was not
properly reaped, thus violating its own rules.
The solution is to skip SHOW WARNINGS if a connection has
not been properly repeaed.
valgrind pointed to a buffer allocated by my_realloc which looked fishy
Replaced size with what was probably intended, added test case.
Now also fixed line after review comment
The reason for the bug is that mysqtest as well as other client tools
running in test suite (mysqlbinlog, mysqldump) will first try to connect
whatever database has created shared memory with default base name
"MySQL" and use this. (Same effect could be seen on Unix if mtr would
not care to calculate "port" and "socket" parameter).
The fix ensures that all client tools and running in mtr use unique
per-database shared memory base parameters, so there is no possibility
to clash with already installed one. We use socket name for shared memory
base (it's known to be unique). This shared-memory-base is written to the
MTR config file to the [client] and [mysqld] sections. Fix made also made
sure all client tools understand and correctly handle --shared-memory-base.
Prior to this patch it was not the case for mysqltest, mysqlbinlog and
mysql_client_test.
All new connections done from mtr scripts via connect() will by default
set shared-memory-base. And finally, there is a possibility to force
shared memory or pipe connection and overwrite shared memory/pipe base name
from within mtr scripts via optional PIPE or SHM modifier. This functionality
was manually backported from 6.0
(original patch http://lists.mysql.com/commits/74749)
a "if"
Bug #41913 mysqltest cannot source files from if inside while
Some commands require additional processing which only works first time
Keep content for write_file or append_file with the st_command struct
Add tests for those cases to mysqltest.test
