Fix assorted warnings that are generated in optimized builds.
Most of it is silencing variables that are set but unused.
This patch also introduces the MY_ASSERT_UNREACHABLE macro
which helps the compiler to deduce that a certain piece of
code is unreachable.
include/my_compiler.h:
Use GCC's __builtin_unreachable if available. It allows
GCC to deduce the unreachability of certain code paths,
thus avoiding warnings that, for example, accused that a
variable could be used without being initialized (due to
unreachable code paths).
Bug#54678: InnoDB, TRUNCATE, ALTER, I_S SELECT, crash or deadlock
- Incompatible change: truncate no longer resorts to a row by
row delete if the storage engine does not support the truncate
method. Consequently, the count of affected rows does not, in
any case, reflect the actual number of rows.
- Incompatible change: it is no longer possible to truncate a
table that participates as a parent in a foreign key constraint,
unless it is a self-referencing constraint (both parent and child
are in the same table). To work around this incompatible change
and still be able to truncate such tables, disable foreign checks
with SET foreign_key_checks=0 before truncate. Alternatively, if
foreign key checks are necessary, please use a DELETE statement
without a WHERE condition.
Problem description:
The problem was that for storage engines that do not support
truncate table via a external drop and recreate, such as InnoDB
which implements truncate via a internal drop and recreate, the
delete_all_rows method could be invoked with a shared metadata
lock, causing problems if the engine needed exclusive access
to some internal metadata. This problem originated with the
fact that there is no truncate specific handler method, which
ended up leading to a abuse of the delete_all_rows method that
is primarily used for delete operations without a condition.
Solution:
The solution is to introduce a truncate handler method that is
invoked when the engine does not support truncation via a table
drop and recreate. This method is invoked under a exclusive
metadata lock, so that there is only a single instance of the
table when the method is invoked.
Also, the method is not invoked and a error is thrown if
the table is a parent in a non-self-referencing foreign key
relationship. This was necessary to avoid inconsistency as
some integrity checks are bypassed. This is inline with the
fact that truncate is primarily a DDL operation that was
designed to quickly remove all data from a table.
mysql-test/suite/innodb/t/innodb-truncate.test:
Add test cases for truncate and foreign key checks.
Also test that InnoDB resets auto-increment on truncate.
mysql-test/suite/innodb/t/innodb.test:
FK is not necessary, test is related to auto-increment.
Update error number, truncate is no longer invoked if
table is parent in a FK relationship.
mysql-test/suite/innodb/t/innodb_mysql.test:
Update error number, truncate is no longer invoked if
table is parent in a FK relationship.
Use delete instead of truncate, test is used to check
the interaction of FKs, triggers and delete.
mysql-test/suite/parts/inc/partition_check.inc:
Fix typo.
mysql-test/suite/sys_vars/t/foreign_key_checks_func.test:
Update error number, truncate is no longer invoked if
table is parent in a FK relationship.
mysql-test/t/mdl_sync.test:
Modify test case to reflect and ensure that truncate takes
a exclusive metadata lock.
mysql-test/t/trigger-trans.test:
Update error number, truncate is no longer invoked if
table is parent in a FK relationship.
sql/ha_partition.cc:
Reorganize the various truncate methods. delete_all_rows is now
passed directly to the underlying engines, so as truncate. The
code responsible for truncating individual partitions is moved
to ha_partition::truncate_partition, which is invoked when a
ALTER TABLE t1 TRUNCATE PARTITION p statement is executed.
Since the partition truncate no longer can be invoked via
delete, the bitmap operations are not necessary anymore. The
explicit reset of the auto-increment value is also removed
as the underlying engines are now responsible for reseting
the value.
sql/handler.cc:
Wire up the handler truncate method.
sql/handler.h:
Introduce and document the truncate handler method. It assumes
certain use cases of delete_all_rows.
Add method to retrieve the list of foreign keys referencing a
table. Method is used to avoid truncating tables that are
parent in a foreign key relationship.
sql/share/errmsg-utf8.txt:
Add error message for truncate and FK.
sql/sql_lex.h:
Introduce a flag so that the partition engine can detect when
a partition is being truncated. Used to give a special error.
sql/sql_parse.cc:
Function mysql_truncate_table no longer exists.
sql/sql_partition_admin.cc:
Implement the TRUNCATE PARTITION statement.
sql/sql_truncate.cc:
Change the truncate table implementation to use the new truncate
handler method and to not rely on row-by-row delete anymore.
The truncate handler method is always invoked with a exclusive
metadata lock. Also, it is no longer possible to truncate a
table that is parent in some non-self-referencing foreign key.
storage/archive/ha_archive.cc:
Rename method as the description indicates that in the future
this could be a truncate operation.
storage/blackhole/ha_blackhole.cc:
Implement truncate as no operation for the blackhole engine in
order to remain compatible with older releases.
storage/federated/ha_federated.cc:
Introduce truncate method that invokes delete_all_rows.
This is required to support partition truncate as this
form of truncate does not implement the drop and recreate
protocol.
storage/heap/ha_heap.cc:
Introduce truncate method that invokes delete_all_rows.
This is required to support partition truncate as this
form of truncate does not implement the drop and recreate
protocol.
storage/ibmdb2i/ha_ibmdb2i.cc:
Introduce truncate method that invokes delete_all_rows.
This is required to support partition truncate as this
form of truncate does not implement the drop and recreate
protocol.
storage/innobase/handler/ha_innodb.cc:
Rename delete_all_rows to truncate. InnoDB now does truncate
under a exclusive metadata lock.
Introduce and reorganize methods used to retrieve the list
of foreign keys referenced by a or referencing a table.
storage/myisammrg/ha_myisammrg.cc:
Introduce truncate method that invokes delete_all_rows.
This is required in order to remain compatible with earlier
releases where truncate would resort to a row-by-row delete.
Use UNINIT_VAR workaround instead of LINT_INIT. The former can
also be used to silence false-positives in non-debug builds as
it actually does not cause new code to be generated.
Problem: trailing spaces were stripped using 8-bit code,
so the truncation result length was incorrect, which led
to an assertion failure.
Fix: using multi-byte safe code.
Fix warnings flagged by the new warning option -Wunused-but-set-variable
that was added to GCC 4.6 and that is enabled by -Wunused and -Wall. The
option causes a warning whenever a local variable is assigned to but is
later unused. It also warns about meaningless pointer dereferences.
client/mysql.cc:
Meaningless pointer dereferences.
client/mysql_upgrade.c:
Check whether reading from the file succeeded.
extra/comp_err.c:
Unused.
extra/yassl/src/yassl_imp.cpp:
Skip instead of reading data that is discarded.
include/my_pthread.h:
Variable is only used in debug builds.
include/mysys_err.h:
Add new error messages.
mysys/errors.c:
Add new error message for permission related functions.
mysys/mf_iocache.c:
Variable is only checked under THREAD.
mysys/my_copy.c:
Raise a error if chmod or chown fails.
mysys/my_redel.c:
Raise a error if chmod or chown fails.
regex/engine.c:
Use a equivalent variable for the assert.
server-tools/instance-manager/instance_options.cc:
Unused.
sql/field.cc:
Unused.
sql/item.cc:
Unused.
sql/log.cc:
Do not ignore the return value of freopen: only set buffer if
reopening succeeds.
Adjust doxygen comment to the right function.
Pass message lenght to log function.
sql/mysqld.cc:
Do not ignore the return value of freopen: only set buffer if
reopening succeeds.
sql/partition_info.cc:
Unused.
sql/slave.cc:
No need to set pointer to the address of '\0'.
sql/spatial.cc:
Unused. Left for historical purposes.
sql/sql_acl.cc:
Unused.
sql/sql_base.cc:
Pointers are always set to the same variables.
sql/sql_parse.cc:
End statement if reading fails.
Store the buffer after it has actually been updated.
sql/sql_repl.cc:
No need to set pointer to the address of '\0'.
sql/sql_show.cc:
Put variable under the same ifdef block.
sql/udf_example.c:
Set null pointer flag appropriately.
storage/csv/ha_tina.cc:
Meaningless dereferences.
storage/example/ha_example.cc:
Return the error since it's available.
storage/myisam/mi_locking.c:
Remove unused and dead code.
Essentially, the problem is that safemalloc is excruciatingly
slow as it checks all allocated blocks for overrun at each
memory management primitive, yielding a almost exponential
slowdown for the memory management functions (malloc, realloc,
free). The overrun check basically consists of verifying some
bytes of a block for certain magic keys, which catches some
simple forms of overrun. Another minor problem is violation
of aliasing rules and that its own internal list of blocks
is prone to corruption.
Another issue with safemalloc is rather the maintenance cost
as the tool has a significant impact on the server code.
Given the magnitude of memory debuggers available nowadays,
especially those that are provided with the platform malloc
implementation, maintenance of a in-house and largely obsolete
memory debugger becomes a burden that is not worth the effort
due to its slowness and lack of support for detecting more
common forms of heap corruption.
Since there are third-party tools that can provide the same
functionality at a lower or comparable performance cost, the
solution is to simply remove safemalloc. Third-party tools
can provide the same functionality at a lower or comparable
performance cost.
The removal of safemalloc also allows a simplification of the
malloc wrappers, removing quite a bit of kludge: redefinition
of my_malloc, my_free and the removal of the unused second
argument of my_free. Since free() always check whether the
supplied pointer is null, redudant checks are also removed.
Also, this patch adds unit testing for my_malloc and moves
my_realloc implementation into the same file as the other
memory allocation primitives.
client/mysqldump.c:
Pass my_free directly as its signature is compatible with the
callback type -- which wasn't the case for free_table_ent.
Apart strict-aliasing warnings, fix the remaining warnings
generated by GCC 4.4.4 -Wall and -Wextra flags.
One major source of warnings was the in-house function my_bcmp
which (unconventionally) took pointers to unsigned characters
as the byte sequences to be compared. Since my_bcmp and bcmp
are deprecated functions whose only difference with memcmp is
the return value, every use of the function is replaced with
memcmp as the special return value wasn't actually being used
by any caller.
There were also various other warnings, mostly due to type
mismatches, missing return values, missing prototypes, dead
code (unreachable) and ignored return values.
BUILD/SETUP.sh:
Remove flags that are implied by -Wall and -Wextra.
Do not warn about unused parameters in C++.
BUILD/check-cpu:
Print only the compiler version instead of verbose banner.
Although the option is gcc specific, the check was only
being used for GCC specific checks anyway.
client/mysql.cc:
bcmp is no longer defined.
client/mysqltest.cc:
Pass a string to function expecting a format string.
Replace use of bcmp with memcmp.
cmd-line-utils/readline/Makefile.am:
Always define _GNU_SOURCE when compiling GNU readline.
Required to make certain prototypes visible.
cmd-line-utils/readline/input.c:
Condition for the code to be meaningful.
configure.in:
Remove check for bcmp.
extra/comp_err.c:
Use appropriate type.
extra/replace.c:
Replace use of bcmp with memcmp.
extra/yassl/src/crypto_wrapper.cpp:
Do not ignore the return value of fgets. Retrieve the file
position if fgets succeed -- if it fails, the function will
bail out and return a error.
extra/yassl/taocrypt/include/blowfish.hpp:
Use a single array instead of accessing positions of the sbox_
through a subscript to pbox_.
extra/yassl/taocrypt/include/runtime.hpp:
One definition of such functions is enough.
extra/yassl/taocrypt/src/aes.cpp:
Avoid potentially ambiguous conditions.
extra/yassl/taocrypt/src/algebra.cpp:
Rename arguments to avoid shadowing related warnings.
extra/yassl/taocrypt/src/blowfish.cpp:
Avoid potentially ambiguous conditions.
extra/yassl/taocrypt/src/integer.cpp:
Do not define type within a anonymous union.
Use a variable to return a value instead of
leaving the result in a register -- compiler
does not know the logic inside the asm.
extra/yassl/taocrypt/src/misc.cpp:
Define handler for pure virtual functions.
Remove unused code.
extra/yassl/taocrypt/src/twofish.cpp:
Avoid potentially ambiguous conditions.
extra/yassl/testsuite/test.hpp:
Function must have C language linkage.
include/m_string.h:
Remove check which relied on bcmp being defined -- they weren't
being used as bcmp is only visible when _BSD_SOURCE is defined.
include/my_bitmap.h:
Remove bogus helpers which were used only in a few files and
were causing warnings about dead code.
include/my_global.h:
Due to G++ bug, always silence false-positive uninitialized
variables warnings when compiling C++ code with G++.
Remove bogus helper.
libmysql/Makefile.shared:
Remove built-in implementation of bcmp.
mysql-test/lib/My/SafeProcess/safe_process.cc:
Cast pid to largest possible type for a process identifier.
mysys/mf_loadpath.c:
Leave space of the ending nul.
mysys/mf_pack.c:
Replace bcmp with memcmp.
mysys/my_bitmap.c:
Dead code removal.
mysys/my_gethwaddr.c:
Remove unused variable.
mysys/my_getopt.c:
Silence bogus uninitialized variable warning.
Do not cast away the constant qualifier.
mysys/safemalloc.c:
Cast to expected type.
mysys/thr_lock.c:
Silence bogus uninitialized variable warning.
sql/field.cc:
Replace bogus helper with a more appropriate logic which is
used throughout the code.
sql/item.cc:
Remove bogus logical condition which always evaluates to TRUE.
sql/item_create.cc:
Simplify code to avoid signedness related warnings.
sql/log_event.cc:
Replace use of bcmp with memcmp.
No need to use helpers for simple bit operations.
sql/log_event_old.cc:
Replace bmove_align with memcpy.
sql/mysqld.cc:
Move use declaration of variable to the ifdef block where it
is used. Remove now-unnecessary casts and arguments.
sql/set_var.cc:
Replace bogus helpers with simple and classic bit operations.
sql/slave.cc:
Cast to expected type and silence bogus warning.
sql/sql_class.h:
Don't use enum values as bit flags, the supposed type safety is
bogus as the combined bit flags are not a value in the enumeration.
sql/udf_example.c:
Only declare variable when necessary.
sql/unireg.h:
Replace use of bmove_align with memcpy.
storage/innobase/os/os0file.c:
Silence bogus warning.
storage/myisam/mi_open.c:
Remove bogus cast, DBUG_DUMP expects a pointer to unsigned
char.
storage/myisam/mi_page.c:
Remove bogus cast, DBUG_DUMP expects a pointer to unsigned
char.
strings/bcmp.c:
Remove built-in bcmp.
strings/ctype-ucs2.c:
Silence bogus warning.
tests/mysql_client_test.c:
Use a appropriate type as expected by simple_command().
and a backport of relevant changes from the 6.0
version of the fix done by Ingo Struewing.
The bug itself was fixed by the patch for Bug#54811.
MyISAMMRG engine would try to use MMAP on its children
even on platforms that don't support it and even if
myisam_use_mmap option was off.
This lead to an infinite hang in INSERT ... SELECT into
a MyISAMMRG table when the destination MyISAM table
was also selected from.
A bug in duplicate detection fixed by 54811 was essential to
the hang - when a duplicate is detected, the optimizer
disables the use of memory mapped files, and it wasn't the case.
The patch below is also to not turn on MMAP on children tables
if myisam_use_mmap is off.
A test case is added to cover MyISAMMRG and myisam_use_mmap
option.
mysql-test/r/merge_mmap.result:
Result file - Bug#50788.
mysql-test/t/merge_mmap-master.opt:
An option file for the test for Bug#50788 -- use mmap.
mysql-test/t/merge_mmap.test:
Try INSERT ... SELECT into a merge table when myisam_use_mmap is on (Bug#50788).
storage/myisam/mi_statrec.c:
Fixed misinterpretation of the return value of my_b_read().
storage/myisammrg/ha_myisammrg.cc:
Skip HA_EXTRA_MMAP if MyISAM memory mapping is disabled.
Bug#47633 - assert in ha_myisammrg::info during OPTIMIZE
The server crashed on an attempt to optimize a MERGE table with
non-existent child table.
mysql_admin_table() relied on the table to be successfully open
if a table object had been allocated.
Changed code to check return value of the open function before
calling a handler:: function on it.
mysql-test/r/merge.result:
Backport of revid:ingo.struewing@sun.com-20091223200354-r2uzbdkj2v6yv111
Bug#47633 - assert in ha_myisammrg::info during OPTIMIZE
Updated result file.
mysql-test/t/merge.test:
Backport of revid:ingo.struewing@sun.com-20091223200354-r2uzbdkj2v6yv111
Bug#47633 - assert in ha_myisammrg::info during OPTIMIZE
Changed tests to respect changed TEMPORARY MERGE locking (unrelated).
Changed tests to respect changed CREATE TABLE ... LIKE (unrelated).
Changed tests to respect that no new tables can be created
under LOCK TABLE (unrelated).
Added test for Bug#47633.
Changed error numbers to symbolic names.
Added test for child locking for ALTER under LOCK TABLE.
Since Bug 36171 is not pushed yet, not the whole patch has been backported.
mysys/my_delete.c:
Backport of revid:ingo.struewing@sun.com-20091223200354-r2uzbdkj2v6yv111
Bug#47633 - assert in ha_myisammrg::info during OPTIMIZE
Fixed error reporting.
Fixed indentation.
mysys/my_mmap.c:
Backport of revid:ingo.struewing@sun.com-20091223200354-r2uzbdkj2v6yv111
Bug#47633 - assert in ha_myisammrg::info during OPTIMIZE
Added DBUG.
sql/item_func.cc:
Backport of revid:ingo.struewing@sun.com-20091223200354-r2uzbdkj2v6yv111
Added Debug Sync point, required by merge_sync.test.
sql/sql_table.cc:
Backport of revid:ingo.struewing@sun.com-20091223200354-r2uzbdkj2v6yv111
Bug#47633 - assert in ha_myisammrg::info during OPTIMIZE
Do not call handler:: functions if the table was not opened
successfully.
Added Debug Sync point, required by merge_sync.test.
storage/myisam/mi_check.c:
Backport of revid:ingo.struewing@sun.com-20091223200354-r2uzbdkj2v6yv111
Bug#47633 - assert in ha_myisammrg::info during OPTIMIZE
Unmap memory before exchanging data files. Needed on Windows.
storage/myisammrg/ha_myisammrg.cc:
Backport of revid:ingo.struewing@sun.com-20091223200354-r2uzbdkj2v6yv111
Added Debug Sync point, required by merge_sync.test.
merge_sync.test will be introduced by a patch for Bug 36171,
which is not pushed yet.
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.
client/mysql.cc:
Remove now-unnecessary casts.
Break up large strings.
client/mysql_upgrade.c:
Remove now-unnecessary casts.
client/mysqladmin.cc:
Remove now-unnecessary casts.
Break up large strings.
client/mysqlbinlog.cc:
Remove now-unnecessary casts.
client/mysqlcheck.c:
Remove now-unnecessary casts.
client/mysqldump.c:
Remove now-unnecessary casts.
client/mysqlimport.c:
Remove now-unnecessary casts.
client/mysqlshow.c:
Remove now-unnecessary casts.
client/mysqlslap.c:
Remove now-unnecessary casts.
client/mysqltest.cc:
Remove now-unnecessary casts.
extra/comp_err.c:
Remove now-unnecessary casts.
extra/my_print_defaults.c:
Remove now-unnecessary casts.
Break up large strings.
extra/mysql_waitpid.c:
Remove now-unnecessary casts.
extra/perror.c:
Remove now-unnecessary casts.
extra/resolve_stack_dump.c:
Remove now-unnecessary casts.
extra/resolveip.c:
Remove now-unnecessary casts.
include/my_getopt.h:
Use a void pointer type as the opaque type to avoid problems with type
incompatibility -- GCC issues warnings when the type name is not type
compatible with a operand. As a side bonus, a explicit cast won't be
necessary anymore.
include/sslopt-longopts.h:
Remove now-unnecessary casts.
Break up large strings.
mysys/my_getopt.c:
Update opaque type and introduce a type definition for the
argument to my_getopt_register_get_addr.
server-tools/instance-manager/options.cc:
Remove now-unnecessary casts.
sql/mysqld.cc:
Remove now-unnecessary casts.
Break up large strings.
Update mysql_getopt_value prototype (the old prototype
was different from the definition anyway).
sql/sql_plugin.cc:
The type of a pointer to a function must be compatible with the
pointed-to function type, otherwise the behavior is undefined.
sql/table.cc:
The variable buf pointer to pointer to pointer to constant char
could improperly alias a incompatible type in call to fix_type_
pointers. Since this was actually dead code, it is simply removed.
sql/unireg.cc:
Remove call to get_form_pos. The code creates a new FRM file which
is always truncated and writes the form position as 0. Hence, no
need to retrieve it, we now for sure it is 0.
storage/archive/archive_reader.c:
Remove now-unnecessary casts.
storage/myisam/ft_nlq_search.c:
Read weight directly from the buffer.
storage/myisam/fulltext.h:
Add explanation about the type duality of a key buffer.
Add accessor macro to retrieve a FT float value.
storage/myisam/mi_test1.c:
Remove now-unnecessary casts.
storage/myisam/myisam_ftdump.c:
Read weight directly from the buffer.
storage/myisam/myisamchk.c:
Remove now-unnecessary casts.
storage/myisam/myisamlog.c:
A pointer to char was used to alias a pointer to pointer to
unsigned char, thus violating strict aliasing rules.
storage/myisam/myisampack.c:
Remove now-unnecessary casts.
strings/decimal.c:
Remove aliasing violation, printing the value is enough for
debugging purposes.
tests/mysql_client_test.c:
Remove now-unnecessary casts.
information_schema query.
Porting a fix done for a feature tree by Ingo Struewing.
No test case since the crash only occurs under a stress
load.
storage/myisam/mi_dbug.c:
Iterate over the list of MyISAM shares and access the MyISAM
share internals under a lock.
Add -Wall to gcc/g++
Fix most warnings reported in dbg and opt mode.
cmd-line-utils/libedit/filecomplete.c:
Remove unused auto variables.
configure.cmake:
Add -Wall to gcc.
extra/comp_err.c:
Cast to correct type.
extra/perror.c:
Fix segfault (but warnings about deprecated features remain)
extra/yassl/taocrypt/include/runtime.hpp:
Comparing two literals was reported as undefined behaviour.
include/my_global.h:
Add a template for aligning character buffers.
mysys/lf_alloc-pin.c:
Initialize pointer.
sql/mysqld.cc:
Use UNINIT_VAR rather than LINT_INIT.
sql/partition_info.cc:
Use UNINIT_VAR rather than LINT_INIT.
sql/rpl_handler.cc:
Use char[] rather than unsigned long[] array for placement buffer.
sql/spatial.cc:
Use char[] rather than unsigned void*[] array for placement buffer.
sql/spatial.h:
Use char[] rather than unsigned void*[] array for placement buffer.
sql/sql_partition.cc:
Initialize auto variable.
sql/sql_table.cc:
Initialize auto variables.
Add parens around assignment within if()
sql/sys_vars.cc:
Use UNINIT_VAR.
storage/innobase/os/os0file.c:
Init first slot in auto variable.
storage/myisam/mi_create.c:
Use UNINIT_VAR rather than LINT_INIT.
storage/myisam/mi_open.c:
Remove (wrong) casting.
storage/myisam/mi_page.c:
Remove (wrong) casting.
storage/myisam/mi_search.c:
Cast to uchar* rather than char*.
strings/ctype-ucs2.c:
Use UNINIT_VAR rather than LINT_INIT.
Add (uchar*) casting.
(make relies GNU extentions). The patch was partially
backport from 6.0.
Original comment:
bug#30708: make relies GNU extensions. Now that we no longer use
BitKeeper we can safely remove the SCCS handling with no loss of
functionality.
even if myisam-recover is OFF
The problem was that a corrupted MyISAM table was auto repaired
even if the myisam_recover_options server variable (or the
myisam_recover option) was set to OFF.
The reason was that the auto_repair() function, which is supposed
to say if auto repair is to be used, did not use the server variable
setting correctly. This bug was a regression introduced by WL#4738.
This patch fixes the problem by making sure auto_repair() returns
FALSE if myisam_recover_options is set to OFF.
Test case added to myisam.test.
