-Wunused-but-set-variable -Warray-bounds warnings

[Laurynas Biveinis]

5.5 trunk:

/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/ubuntu-precise-32bit/strings/ctype-ucs2.c: In function ‘my_fill_utf32’:
/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/ubuntu-precise-32bit/strings/ctype-ucs2.c:2321:8: warning: variable ‘buflen’ set but not used [-Wunused-but-set-variable]

/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/ubuntu-precise-32bit/sql/filesort.cc: In function ‘void make_sortkey(SORTPARAM*, uchar*, uchar*)’:
/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/ubuntu-precise-32bit/sql/filesort.cc:872:16: warning: variable ‘tmp_length’ set but not used [-Wunused-but-set-variable]

/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/ubuntu-precise-32bit/sql/slave.cc: In function ‘int terminate_slave_thread(THD*, mysql_mutex_t*, mysql_cond_t*, volatile uint*, bool)’:
/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/ubuntu-precise-32bit/sql/slave.cc:665:9: warning: variable ‘error’ set but not used [-Wunused-but-set-variable]

For fix, partially backport

commit bccdbcba25ec4fead4ae630efd8fb2885e1aaa30
Author: Tor Didriksen <email address hidden>
Date: Fri Feb 13 10:02:59 2015 +0100

    Bug#20458574 FIX ALL THE ARRAY BOUNDS WARNINGS

    Remove compiler warnings when building in optimized mode:

    In strings/decimal.c fix numerous warnings of the type:
    array subscript is below array bounds [-Werror=array-bounds]
    This part of the patch is based on a patch
    from https://github.com/webscalesql/webscalesql-5.6
    That patch added some bounds-checks for loops, and worked for
    gcc4.8.3 but not for gcc 4.9.1 so it was re-written to unroll the loops instead.

    In other source files, fix numerous warnings of the type:
    variable XX set but not used [-Werror=unused-but-set-variable]
    variable XX may be used uninitialized in this function [-Werror=maybe-uninitialized]
    These were variables used only for debugging purposes,
    or variables not proven to be set by all execution paths.

    Compiled with gcc 4.7.2 4.8.3 4.9.1 in optimized mode, with -Wall -Werror

[Laurynas Biveinis (laurynas-biveinis)]

The same backport also fixes

/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/debian-jessie-64bit/strings/decimal.c: In function ‘do_div_mod’:
/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/debian-jessie-64bit/strings/decimal.c:2145:55: warning: array subscript is below array bounds [-Warray-bounds]
   for (i= (prec2 - 1) % DIG_PER_DEC1; *buf2 < powers10[i--]; prec2--) ;
                                                       ^
/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/debian-jessie-64bit/strings/decimal.c:2160:52: warning: array subscript is below array bounds [-Warray-bounds]
   for (i=(prec1-1) % DIG_PER_DEC1; *buf1 < powers10[i--]; prec1--) ;
                                                    ^
/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/debian-jessie-64bit/strings/decimal.c:2145:55: warning: array subscript is below array bounds [-Warray-bounds]
   for (i= (prec2 - 1) % DIG_PER_DEC1; *buf2 < powers10[i--]; prec2--) ;
                                                       ^
/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/debian-jessie-64bit/strings/decimal.c:2160:52: warning: array subscript is below array bounds [-Warray-bounds]
   for (i=(prec1-1) % DIG_PER_DEC1; *buf1 < powers10[i--]; prec1--) ;

/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/debian-jessie-64bit/strings/decimal.c: In function ‘decimal_actual_fraction’:
/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/debian-jessie-64bit/strings/decimal.c:300:26: warning: array subscript is above array bounds [-Warray-bounds]
          *buf0 % powers10[i++] == 0;
                          ^
/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/debian-jessie-64bit/strings/decimal.c:300:26: warning: array subscript is above array bounds [-Warray-bounds]
[ 12%] Building C object strings/CMakeFiles/strings.dir/longlong2str.c.o
/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/debian-jessie-64bit/strings/decimal.c: In function ‘decimal2string’:
/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/debian-jessie-64bit/strings/decimal.c:264:56: warning: array subscript is below array bounds [-Warray-bounds]
     for (i= (intg - 1) % DIG_PER_DEC1; *buf0 < powers10[i--]; intg--) ;
                                                        ^
/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/debian-jessie-64bit/strings/decimal.c:264:56: warning: array subscript is below array bounds [-Warray-bounds]
[ 12%] Building C object strings/CMakeFiles/strings.dir/my_strtoll10.c.o
[ 12%] Building C object strings/CMakeFiles/strings.dir/my_vsnprintf.c.o
[ 12%] Building C object strings/CMakeFiles/strings.dir/str2int.c.o
/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/debian-jessie-64bit/strings/decimal.c: In function ‘decimal2bin’:
/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/release/Host/debian-jessie-64bit/strings/decimal.c:264:56: warning: array subscript is below array bounds [-Warray-bounds]
     for (i= (intg - 1) % DIG_PER_DEC1; *buf0 < powers10[i--]; intg--) ;q
/mnt/workspace/percona-server-5.5-trunk/BUILD_TYPE/re...

[Laurynas Biveinis (laurynas-biveinis)]

     https://github.com/percona/percona-server/pull/896
     https://github.com/percona/percona-server/pull/897
     https://github.com/percona/percona-server/pull/898

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PS-3527