Change the default optimization level for Sun Studio to "-O1". 
This is a workaround for a Sun Studio bug (see bug #41710 
comments for details): 
 
1. Use $GCC instead of $ac_cv_prog_gcc to check for gcc, since 
the first one is the only documented way to do it. 
 
2. Use $GXX instead of $ac_cv_prog_cxx_g to check for g++, 
since the latter is set to "yes" when the C++ compiler accepts 
"-g" which is the case for both g++ and CC. 
 
3. When building with Sun Studio, set the default values for 
CFLAGS/CXXFLAGS to "-O1", since unlike GCC, Sun Studio 
interprets "-O" as "-xO3" (see the manual pages for cc and CC). 

with gcc 4.3.2
      
Compiling MySQL with gcc 4.3.2 and later produces a number of 
warnings, many of which are new with the recent compiler
versions.
                  
This bug will be resolved in more than one patch to limit the
size of changesets. This is the second patch, fixing more
of the warnings.

crashes server!

The problem affects the scenario when index merge is followed by a filesort
and the sort buffer is not big enough for all the sort keys.
In this case the filesort function will read the data to the end through the 
index merge quick access method (and thus closing the cursor etc), 
but will leave the pointer to the quick select method in place.
It will then create a temporary file to hold the results of the filesort and
will add it as a sort output file (in sort.io_cache).
Note that filesort will copy the original 'sort' structure in an automatic
variable and restore it after it's done.
As a result at exiting filesort() we have a sort.io_cache filled in and 
nothing else (as a result of close of the cursors at end of reading data 
through index merge).
Now create_sort_index() will note that there is a select and will clean it up
(as it's been used already by filesort() reading the data in). While doing that
a special case in the index merge destructor will clean up the sort.io_cache,
assuming it's an output of the index merge method and is not needed anymore.
As a result the code that tries to read the data back from the filesort output 
will get no data in both memory and disk and will crash.
      
Fixed similarly to how filesort() does it : by copying the sort.io_cache structure
to a local variable, removing the pointer to the io_cache (so that it's not freed 
by QUICK_INDEX_MERGE_SELECT::~QUICK_INDEX_MERGE_SELECT) and restoring the original 
structure (together with the valid pointer) after the cleanup is done.
This is a safe thing to do because all the structures are already cleaned up by
hitting the end of the index merge's read method (QUICK_INDEX_MERGE_SELECT::get_next()) 
and the cleanup code being written in a way that tolerates repeating cleanups.

WHERE and GROUP BY clause

Loose index scan may use range conditions on the argument of 
the MIN/MAX aggregate functions to find the beginning/end of 
the interval that satisfies the range conditions in a single go.
These range conditions may have open or closed minimum/maximum 
values. When the comparison returns 0 (equal) the code should 
check the type of the min/max values of the current interval 
and accept or reject the row based on whether the limit is 
open or not.
There was a wrong composite condition on checking this and it was
not working in all cases.
Fixed by simplifying the conditions and reversing the logic.

Backport to MySQL 5.0/1 fix by Vladislav Vaintroub:

In Vista and later and also in when using terminal services, when
server is started from  command line, client cannot connect to it
via shared memory protocol.

This is a regression introduced when  Bug#24731 was fixed.  The
reason is that client is trying to attach to shared memory using
global kernel object  namespace (all kernel objects are prefixed
with Global\). However, server started from the command line in
Vista and later will create shared memory and events using current
session namespace. Thus, client is unable to find the server and
connection fails.

The fix for the client is to first try to find server using "local"
names  (omitting Global\  prefix) and only if server is not found,
trying global namespace.

            memory issue ? 
 
The mysql command line client could misinterpret some character 
sequences as commands under some circumstances. 
 
The upper limit for internal readline buffer was raised to 1 GB 
(the same as for server's max_allowed_packet) so that any input 
line is processed by add_line() as a whole rather than in 
chunks.

with gcc 4.3.2
      
Compiling MySQL with gcc 4.3.2 and later produces a number of 
warnings, many of which are new with the recent compiler
versions.
      
This bug will be resolved in more than one patch to limit the
size of changesets. This is the first patch, fixing a number 
of the warnings, predominantly "suggest using parentheses 
around && in ||", and empty for and while bodies.

Implemented a way to circumvent the always true comparison by
having nested macros (as suggested on review).

Fixed the 5.0-bugteam MacOSX warnings.

Holding on to the temporary inno hash index latch is an optimization in
many cases, but a pessimization in some others.

Release temporary latches for those corner cases we (or rather, or customers,
thanks!) have identified, that is, when we are about to do something that
might take a really long time, like REPAIR or filesort.

When copying the Item class one must copy its attributes as well.

The crash happens because of uninitialized
lex->ssl_cipher, lex->x509_subject, lex->x509_issuer variables.
The fix is to add initialization of these variables for
stored procedures&functions.

The crash happens due to wrong max_length value which is set on
Item_func_round::fix_length_and_dec() stage. The value is set to
args[0]->max_length which is too big in case of LONGTEXT(LONGBLOB) fields.
The fix is to set max_length using float_length() function.

BEGIN/COMMIT/ROLLBACK was subject to replication db rules, and
caused the boundary of a transaction not recognized correctly 
when these queries were ignored by the rules.

Fixed the problem by skipping replication db rules for these
statements.

Bug#34309: '_PC' macro redefinition

For reasons that are now a mystery, we had defined a CPP symbol to
help ancient compilers work better (in some way that's lost to history).
This interferes with at least one modern compiler.

Now, don't define the _PC symbol.  Those other underscore-leading
symbols are suspect also, but at least the names aren't inscrutable.
Let's leave them for now.

The fix is to use case insensitive collation
for mysql client command search.