gcc -c  -I./zlib-src ... adler32.c
 adler32.c:12: error: expected declaration specifiers or '...' before '__int64'

##</code><code>##

#if !defined(_WIN32) && (defined(_LARGEFILE64_SOURCE) && _LFS64_LARGEFILE-0)
#  define z_off64_t off64_t
#else
#  if defined(_WIN32)
#    define z_off64_t __int64
#  else
#  define z_off64_t z_off_t
#endif
#endif

##</code><code>##

#if !defined(_WIN32) && (defined(_LARGEFILE64_SOURCE) && _LFS64_LARGEFILE-0)
#  define z_off64_t off64_t
#else
#  if defined(_MSC_VER)              ### this line changed.
#    define z_off64_t __int64
#  else
#  define z_off64_t z_off_t
#endif
#endif