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Frequently Asked Questions about zlib
If your question is not there, please check the zlib home page which may have more recent information.
The lastest zlib FAQ is at
1. Is zlib Y2K-compliant?
Yes. zlib doesn't handle dates.
2. Where can I get a Windows DLL version?
The zlib sources can be compiled without change to produce a DLL. If you
want a precompiled DLL, see . Questions
about the zlib DLL should be sent to Gilles Vollant (
3. Where can I get a Visual Basic interface to zlib?
* contrib/visual-basic.txt in the zlib distribution
4. compress() returns Z_BUF_ERROR
Make sure that before the call of compress, the length of the compressed
buffer is equal to the total size of the compressed buffer and not
zero. For Visual Basic, check that this parameter is passed by reference
("as any"), not by value ("as long").
5. deflate() or inflate() returns Z_BUF_ERROR
Before making the call, make sure that avail_in and avail_out are not
zero. When setting the parameter flush equal to Z_FINISH, also make sure
that avail_out is big enough to allow processing all pending input.
6. Where's the zlib documentation (man pages, etc.)?
It's in zlib.h for the moment, and Francis S. Lin has converted it to a
web page zlib.html. Volunteers to transform this to Unix-style man pages,
please contact Jean-loup Gailly ( Examples of zlib usage
are in the files example.c and minigzip.c.
7. Why don't you use GNU autoconf or libtool or ...?
Because we would like to keep zlib as a very small and simple
package. zlib is rather portable and doesn't need much configuration.
8. I found a bug in zlib.
Most of the time, such problems are due to an incorrect usage of
zlib. Please try to reproduce the problem with a small program and send
the corresponding source to us at . Do not send
multi-megabyte data files without prior agreement.
9. Why do I get "undefined reference to gzputc"?
If "make test" produces something like
example.o(.text+0x154): undefined reference to `gzputc'
check that you don't have old files libz.* in /usr/lib, /usr/local/lib or
/usr/X11R6/lib. Remove any old versions, then do "make install".
10. I need a Delphi interface to zlib.
See the directories contrib/delphi and contrib/delphi2 in the zlib
11. Can zlib handle .zip archives?
See the directory contrib/minizip in the zlib distribution.
12. Can zlib handle .Z files?
No, sorry. You have to spawn an uncompress or gunzip subprocess, or adapt
the code of uncompress on your own.
13. How can I make a Unix shared library?
make clean
./configure -s
14. Why does "make test" fail on Mac OS X?
Mac OS X already includes zlib as a shared library, and so -lz links the
shared library instead of the one that the "make" compiled. For zlib
1.1.3, the two are incompatible due to different compile-time
options. Simply change the -lz in the Makefile to libz.a, and it will use
the compiled library instead of the shared one and the "make test" will
15. I have a question about OttoPDF
We are not the authors of OttoPDF. The real author is on the OttoPDF web
site Joel Hainley