I have not yet succeeded in compiling Python 2.4.2c1 in
64-bit mode on Solaris 10.  I used the following flags
and configuration options, which are the same as what I
used on S9, except for the addition of the
"-xc99=%none" flag to prevent compilation failures due
to some of the other changes from S9 to S10:
setenv CC cc
setenv CXX CC
setenv BASECFLAGS "-native -xc99=%none -xarch=native64
-mt -xO3"
setenv LDFLAGS "-xarch=native64"
./configure --without-gcc

At build time I get these errors:
%  make
cc -c -native -xc99=%none -xarch=native64 -mt -xO3
-DNDEBUG -O -I. -I../Include  -DPy_BUILD_CORE -o
Modules/python.o ../Modules/python.c
"/usr/include/limits.h", line 290: invalid type combination
"/usr/include/limits.h", line 290: warning: useless
declaration
"/usr/include/limits.h", line 290: warning: typedef
declares no type name
"/usr/include/stdio.h", line 146: warning: useless
declaration
"/usr/include/stdio.h", line 146: warning: typedef
declares no type name
"/usr/include/sys/types.h", line 344: warning:
modification of typedef with "int" ignored
"/usr/include/sys/types.h", line 344: invalid type
combination
"/usr/include/sys/types.h", line 344: warning: useless
declaration
"/usr/include/sys/types.h", line 344: warning: typedef
declares no type name
"/usr/include/sys/types.h", line 484: invalid type
combination
"/usr/include/sys/types.h", line 484: warning: useless
declaration
"/usr/include/sys/types.h", line 484: warning: typedef
declares no type name
"../Include/pyport.h", line 612: #error: "LONG_BIT
definition appears wrong for platform (bad gcc/glibc
config?)."
cc: acomp failed for ../Modules/python.c
*** Error code 2
make: Fatal error: Command failed for target
`Modules/python.o'