[Zlib-devel] Re: ABI compatibility of zlib 1.0.x, 1.1.x, and 1.2.x

[Mark Adler]

On Friday, December 5, 2003, at 02:03  PM, Glenn Randers-Pehrson wrote:
> I cannot find any statement on the zlib site (FAQ, announcement) about
> whether zlib 1.2.1 is binary compatible with 1.1.4.  My guess is that
> it's not guaranteed and that applications using the zlib-1.1.4 shared
> library should be relinked.

Good question.  The DLL is definitely not compatible.  As for shared 
libraries, that might depend on what compiler options were used in the 
before and after cases.  Assuming that the only variable is zlib, then 
there is one place where there is a possibility of an incompatibility.  
That is the definition of the z_off_t type used by gzseek() and 
gztell().  Portability improvements in zlib 1.2.1 should make that 
defined as off_t more often than zlib 1.1.4.  This only matters if 
off_t is larger than unsigned long.

Any other comments on this?

mark