MySQL Bugs: #53445: Build with -Wall and fix warnings that it generates

Bug #53445	Build with -Wall and fix warnings that it generates
Submitted:	5 May 2010 17:16	Modified:	14 Oct 2010 14:55
Reporter:	Mark Callaghan	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Compiling	Severity:	S3 (Non-critical)
Version:	5.1, all	OS:	Any
Assigned to:	Davi Arnaut	CPU Architecture:	Any
Tags:	best, practices

Description:
If MySQL is compiled with -Wall and the warnings are fixed then we will prevent some bugs from getting into production releases. This will lower the support costs for MySQL. This will also increase the reputation of MySQL for writing solid code.

How to repeat:
./configure ... C_EXTRA_FLAGS="-DWall"

It would be even better to use -Werror with -Wall

In principle, you are right, and in theory, I have the same opinion. (And complaining about the warnings is part of my job, sometimes.)

But in theory, theory is the same as practice, while in practice, ... well.

There is an ongoing effort to reduce the number of warnings. Currently, we have several thousand warnings on certain platforms. They have a tendency to pop up suddenly, and in groups, long after the code that is being warned about is written. Removing them takes time. At the same time, most of them are just not quite as important as certain other bugs. I'm sure that you would agree on this as well. Unfortunately, we can't tell which ones are important, and fix those first. But we are fixing them, and for internal testing, we are building with -Wall. (Building with -Werror would be quite useless at this stage. I've suggested it too, but right now, it would just block all other work that is being done.)

Btw., there is no internal demand that releases are built without warnings. These builds simply don't happen at a time where it makes sense to still fix them. On the other hand, enabling them could mask more serious deviations. We run hundreds of test builds every day (really), and it makes sense to monitor warnings there; but then, what I said before applies of course, it's still a lot of work.

Daniel, I appreciate the problem in working out which are the most important - however then a productive approach would be "start at the top and keep going". It will indeed take time, and thus the only way to get anywhere is to get started.

By the way, I tried to get this actioned around 2002-2003 when I was in Docs.
As a C coder myself, I know that effectively ignoring warnings can mask serious problems, since a warning *can* indicate a problem however if it's hiding behind thousands of others you won't see it.
If it had been actioned then, we'd be about 8 years ahead of the position the code is now. Hence my suggestion to "just get going".

Drizzle did it, and MariaDB is working on it also. It's very important and should receive resourcing. It'll save money later as it will catch some nasty bugs early.

We have been fixing quite a bunch of compiler warnings for a several months now (5.1 and up, don't expect to on anything below). This is a incremental work and is being performed much before drizzle or whatever. We also not only look into warnings generated by gcc, but by quite a few compilers (some proprietary compilers are quite good at detecting half-backed C++).

On this bug, whether the build team uses -Wall is mostly irrelevant, this is a task of the development team. We (team) generally use build scripts and -Wall enabled and quite a few other flags associated with compiler warnings (look into BUILD/), likewise for the development build system.

Keep in mind that we are also constrained on what can be done for certain structures that are part of the ABI and for warnings that are bogus (gcc has a ton of those. eg: uninitialized related warnings are simply wrong on C++). There are also the difference between versions, et cetera ad infinitum. Fewer compiler warnings is a long term goal.

Anyway, this bug is a bit bogus. Just because we don't advertise it, it doesn't mean its not happening. I can list patches and bug reports if necessary.

One example: Bug#43414 -- five or more patches fixing assorted compiler warnings.

Support for automake silent-rules was also added recently to improve highlighting of warnings.

Some numbers. I've just compiled mysql-5.1-bugteam with -Wall. Number (*) of warnings are:

It generates 102979 compilers warnings -- quite a few are repeated due to warning in headers.
102849 warnings are about unused parameters -- mostly due to headers again, cosmetic stuff (**).
Removing the above leaves us with 130 warnings.
3 are about a implicit declaration in third-party code.
78 about signedness in the usage of my_bcmp.
1 about unused function.
2 about mismatch in expected types.

* Includes warnings for third-party stuff that we ship (readline, yassl, etc).
** There is some internal debate on the usefulness of fixing those in contrast with tempering with revision history, etc. Sometimes we also forget about some nice C++ features..

The CXXFLAGS was based upon BUID/compile-pentium-valgrind-max-no-ndb with -Wall. It uses -O0.

Now the above with -O2 (*):

Total of 103483 compiler generated warnings.
103155 about unused parameter.
Some ~150 in third-party code (array subscript in blowfish.cpp).
Same warnings as described above.
37 warnings about strict-aliasing rules
30 warnings about uninitialized use (a good chunk in C++ code -- that is, bogus).
46 about string literal comparison (in a header, yassl code).

* Rarely used by developers, makes debugging a pain -- gdb problem, latest version should bring some improvements. Slows down compilation too -- a bit relevant, can be worked around with ccache.

The high number of "unused parameter" is mostly due to headers. Should be reduce a bit now due to the header reorganization in trunk. A good chunk (+50% i guess) comes from the item*, field* and handler headers.

Also note that the build scripts we (at least i) developers use are usually derived from -Wall, minus the stuff that does not matter much for us or hinders debuggability (warnings that only work on higher optimization levels) .

FWIW, we could probably introduce -Werror with a temporary exception (via -Wno-error) for the somewhat irrelevant stuff (eg. unused parameter, ..).

Davi,
do it.

We're not only building on GCC btw.
Other compilers are  better at finding warnings and they find different warnings. 
HP compiler is excellent at finding potential bugs, and also Microsoft compiler find stuff that GCC will never find (type size mismatch, for GCC passing pointer to bool instead of bool is just fine not for Microsoft though)

Maybe we can add -Wall and add -Wno* if needed to be sure we don't occasionally miss something important?

About the unused parameters warnings: I was using -Wunused-parameter which is not activated by -Wall by default. So we are around ~150 warnings with -Wall. Mileage may vary depending on specific compiler versions and/or options.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/109194

3059 Tor Didriksen	2010-05-25
      Bug #53445 Build with -Wall and fix warnings that it generates
      
      Add -Wall to gcc/g++
      Fix (almost) all 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.
     @ 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.
     @ strings/dtoa.c
        Perform operations on union variables rather than on doubles.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/109289

3066 Tor Didriksen	2010-05-26
      Bug #53445 Build with -Wall and fix warnings that it generates
      
      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.

Pushed to
bzr+ssh://bk-internal.mysql.com/bzrroot/server/mysql-trunk-bugfixing/

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/109315

3067 Tor Didriksen	2010-05-27
      Bug #53445 Build with -Wall and fix warnings that it generates
      Post-push fix: -Wall implies -Wunused on some platforms,
      which will generate thousands of warnings about unused parameters.
     @ configure.cmake
        Do not warn about unused parameters in C++

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/109434

3071 Davi Arnaut	2010-05-27
      Bug#53445: Build with -Wall and fix warnings that it generates
      
      Fix various mismatches between function's language linkage. Any
      particular function that is declared in C++ but should be callable
      from C must have C linkage. Note that function types with different
      linkages are also distinct. Thus, if a function type is declared in
      C code, it will have C linkage (same if declared in a extern "C"
      block).
     @ client/mysql.cc
        Mismatch between prototype and declaration.
     @ client/mysqltest.cc
        mysqltest used to be C code. Use C linkage where appropriate.
     @ cmd-line-utils/readline/input.c
        Isolate unreachable code.
     @ include/my_alloc.h
        Function type must have C linkage.
     @ include/my_base.h
        Function type must have C linkage.
     @ include/my_global.h
        Add helper macros to avoid spurious namespace indentation.
     @ include/mysql.h.pp
        Update ABI file.
     @ mysys/my_gethwaddr.c
        Remove stray carriage return.
     @ plugin/semisync/semisync_master_plugin.cc
        Callback function types have C linkage.
     @ plugin/semisync/semisync_slave_plugin.cc
        Callback function types have C linkage.
     @ sql/derror.cc
        Expected function type has C linkage.
     @ sql/field.cc
        Use helper macro and fix indentation.
     @ sql/handler.cc
        Expected function type has C linkage.
     @ sql/item_sum.cc
        Correct function linkages. Remove now unnecessary cast.
     @ sql/item_sum.h
        Add prototypes with the appropriate linkage as otherwise they
        are distinct.
     @ sql/mysqld.cc
        Wrapp functions in C linkage mode.
     @ sql/opt_range.cc
        C language linkage is ignored for class member functions.
     @ sql/partition_info.cc
        Add wrapper functions with C linkage for class member functions.
     @ sql/rpl_utility.h
        Use helper macro and fix indentation.
     @ sql/sql_class.cc
        Use helper macro and fix indentation.
     @ sql/sql_select.cc
        Expected function type has C linkage.
     @ sql/sql_show.cc
        Expected function type has C linkage.
     @ sql/sql_test.cc
        Expected function type has C linkage.
     @ storage/myisammrg/ha_myisammrg.cc
        Expected function type has C linkage.
     @ storage/perfschema/pfs.cc
        PSI headers are declared with C language linkage, which also
        applies to function types.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/109632

3080 Davi Arnaut	2010-05-31
      Bug#53445: Build with -Wall and fix warnings that it generates
      
      Fix various mismatches between function's language linkage. Any
      particular function that is declared in C++ but should be callable
      from C must have C linkage. Note that function types with different
      linkages are also distinct. Thus, if a function type is declared in
      C code, it will have C linkage (same if declared in a extern "C"
      block).
     @ client/mysql.cc
        Mismatch between prototype and declaration.
     @ client/mysqltest.cc
        mysqltest used to be C code. Use C linkage where appropriate.
     @ cmd-line-utils/readline/input.c
        Isolate unreachable code.
     @ include/my_alloc.h
        Function type must have C linkage.
     @ include/my_base.h
        Function type must have C linkage.
     @ include/my_global.h
        Add helper macros to avoid spurious namespace indentation.
     @ include/mysql.h.pp
        Update ABI file.
     @ mysys/my_gethwaddr.c
        Remove stray carriage return and fix coding style.
     @ plugin/semisync/semisync_master_plugin.cc
        Callback function types have C linkage.
     @ plugin/semisync/semisync_slave_plugin.cc
        Callback function types have C linkage.
     @ sql/derror.cc
        Expected function type has C linkage.
     @ sql/field.cc
        Use helper macro and fix indentation.
     @ sql/handler.cc
        Expected function type has C linkage.
     @ sql/item_sum.cc
        Correct function linkages. Remove now unnecessary cast.
     @ sql/item_sum.h
        Add prototypes with the appropriate linkage as otherwise they
        are distinct.
     @ sql/mysqld.cc
        Wrap functions in C linkage mode.
     @ sql/opt_range.cc
        C language linkage is ignored for class member functions.
     @ sql/partition_info.cc
        Add wrapper functions with C linkage for class member functions.
     @ sql/rpl_utility.h
        Use helper macro and fix indentation.
     @ sql/sql_class.cc
        Change type of thd argument -- THD is a class.
        Use helper macro and fix indentation.
     @ sql/sql_class.h
        Change type of thd argument -- THD is a class.
     @ sql/sql_select.cc
        Expected function type has C linkage.
     @ sql/sql_select.h
        Move prototype to sql_test.h
     @ sql/sql_show.cc
        Expected function type has C linkage.
     @ sql/sql_test.cc
        Fix required function prototype and fix coding style.
     @ sql/sql_test.h
        Removed unnecessary export and add another.
     @ storage/myisammrg/ha_myisammrg.cc
        Expected function type has C linkage.
     @ storage/perfschema/pfs.cc
        PSI headers are declared with C language linkage, which also
        applies to function types.

Queued to mysql-trunk-bugfixing. Reset to In Progress to work on 5.1 specific stuff.

Pushed into 5.5.5-m3 (revid:alik@sun.com-20100615080459-smuswd9ooeywcxuc) (version source revid:alik@sun.com-20100615080459-smuswd9ooeywcxuc) (merge vers: 5.5.5-m3) (pib:16)

Pushed into mysql-next-mr (revid:alik@sun.com-20100615080558-cw01bzdqr1bdmmec) (version source revid:alik@sun.com-20100615080431-gu5icn0anrt47dsx) (pib:16)

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/112398

3452 Davi Arnaut	2010-06-28
      Bug#53445: Build with -Wall and fix warnings that it generates
      
      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 built-in function my_bcmp
      which (unconventionally) took pointers to unsigned characters
      as the byte sequences to be compared. Since bcmp is a deprecated
      function 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.
      
      Other warnings were due to type mismatches, missing return values
      and dead code.
     @ 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().

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/112794

3458 Davi Arnaut	2010-07-02
      Bug#53445: Build with -Wall and fix warnings that it generates
      
      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().

Queued to mysql-5.1-bugteam and up.

Automatic compile cycle with -Wall -Wextra -Werror is being set up.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/112811

3459 Davi Arnaut	2010-07-02
      Bug#53445: Build with -Wall and fix warnings that it generates
      
      If bzero is not available, resort to memset. Also, remove dead
      bzero.c

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/113191

3470 Davi Arnaut	2010-07-08
      Bug#53445: Build with -Wall and fix warnings that it generates
      
      Introduce a MySQL maintainer/developer mode that enables
      a set of warning options for the C/C++ compiler. This mode
      is intended to help improve the overall quality of the code.
      
      The warning options are:
      
      C_WARNINGS="-Wall -Wextra -Wunused -Wwrite-strings -Werror"
      CXX_WARNINGS="$C_WARNINGS -Wno-unused-parameter"
     @ config/ac-macros/maintainer.m4
        Add a set of default compiler flags used when in maintainer mode.
     @ configure.in
        Hook into the maintainer mode. Disabled by default.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/113234

3471 Davi Arnaut	2010-07-09
      Bug#53445: Build with -Wall and fix warnings that it generates
      
      Introduce a MySQL maintainer/developer mode that enables
      a set of warning options for the C/C++ compiler. This mode
      is intended to help improve the overall quality of the code.
      
      The warning options are:
      
      C_WARNINGS="-Wall -Wextra -Wunused -Wwrite-strings -Werror"
      CXX_WARNINGS="$C_WARNINGS -Wno-unused-parameter"
      
      Since -Wall is essentially a moving target, autoconf checks
      are not run with warning options enabled, in particualr -Werror.
      This decision might be revisited in the future. The patch also
      fixes a mistake in the makefiles, where automake CXXFLAGS would
      be set to CFLAGS.
     @ config/ac-macros/maintainer.m4
        Add a set of default compiler flags used when in maintainer mode.
     @ configure.in
        Hook into the maintainer mode. Disabled by default.

Automatic builds in MySQL maintainer mode have been setup and are being done after each push. There is even a successful build already. To a moderate extent, this alone ensures that no new warnings are introduced. This bug is done for now.

A note has been added to the 5.1.50 and 5.5.6 changelog: 

Builds of MySQL would generate a large number of warnings.

Pushed into mysql-trunk 5.5.6-m3 (revid:alik@sun.com-20100723121820-jryu2fuw3pc53q9w) (version source revid:vasil.dimov@oracle.com-20100531152341-x2d4hma644icamh1) (merge vers: 5.5.5-m3) (pib:18)

Pushed into mysql-next-mr (revid:alik@sun.com-20100723121929-90e9zemk3jkr2ocy) (version source revid:vasil.dimov@oracle.com-20100531152341-x2d4hma644icamh1) (pib:18)

Already noted in changelog

Pushed into mysql-5.1 5.1.51 (revid:build@mysql.com-20100819151858-muaaor6jojb5ouzj) (version source revid:build@mysql.com-20100819151858-muaaor6jojb5ouzj) (merge vers: 5.1.51) (pib:20)

Pushed into mysql-5.1-telco-7.0 5.1.51-ndb-7.0.20 (revid:martin.skold@mysql.com-20101014082627-jrmy9xbfbtrebw3c) (version source revid:martin.skold@mysql.com-20101014082627-jrmy9xbfbtrebw3c) (merge vers: 5.1.51-ndb-7.0.20) (pib:21)

Pushed into mysql-5.1-telco-6.3 5.1.51-ndb-6.3.39 (revid:martin.skold@mysql.com-20101014083757-5qo48b86d69zjvzj) (version source revid:martin.skold@mysql.com-20101014083757-5qo48b86d69zjvzj) (merge vers: 5.1.51-ndb-6.3.39) (pib:21)

Pushed into mysql-5.1-telco-6.2 5.1.51-ndb-6.2.19 (revid:martin.skold@mysql.com-20101014084420-y54ecj85j5we27oa) (version source revid:martin.skold@mysql.com-20101014084420-y54ecj85j5we27oa) (merge vers: 5.1.51-ndb-6.2.19) (pib:21)

Already documented in the 5.1.50 changelog; no new changelog entries required. setting back to Closed state.