Re: Use of zlib

I am confused. I just checked my backend binary and I don't see any
unusual libs required:

$ ldd postgres
libz.so => /usr/lib/libz.so (0x2833f000)
libncurses.so.5 => /shlib/libncurses.so.5 (0x2834e000)
libdl.so => /shlib/libdl.so (0x2838c000)
libm.so => /shlib/libm.so.0.0 (0x2838f000)
libgcc.so.1 => /shlib/libgcc.so.1 (0x283a0000)
libc.so.2 => /shlib/libc.so.2 (0x283ac000)

The libncurses is a little unusual but I don't see libreadline in there
even though it is on the link line.

Are some OS's adding libs that aren't required by the binary?

---------------------------------------------------------------------------

Andrew Dunstan wrote:
>
>
> Thomas Hallgren wrote:
>
> > Problem:
> > PL/Java use a JVM. On some platforms and with some JVM's (Sun's in
> > particular) a libzip.so is bundled that contains a 1.1.3 version of
> > functions also provided in zlib (why they do this is beyond me, but
> > they do so I'll have to live with it). PostgreSQL is linked with zlib
> > by default. This resuls in a conflict which resuls in a JVM crash.
> >
> > I can circumvein this crash by using LD_PRELOAD to force a load of the
> > JVM bundled libzip.so but I suspect that might result in a crash as
> > soon as PostgreSQL calls on zlib to do something. It's of course
> > possible to configure postgresql with --without-zlib also provided you
> > have accesst o the source.
> >
> > Question:
> > From what I can understand from the documentation, the only utility in
> > PostgreSQL that actually uses zlib is pg_dump? If so, why is the
> > postgres process linked with -lz?
> >
> >
>
> I did a small experiment by installing binutils 2.15 and adding
> -Wl,--as-needed to the LDFLAGS, as Tom had suggested might be useful.
>
> This seemed to work quite well and trimmed back the needed libs quite a
> bit. However, when you configure --with-openssl, libz is again linked in.
>
> Not sure where that leaves us.
>
> cheers
>
> andrew
>
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