Runtime linker ignores RPATH in executable on solaris

I'm trying to compile samtools on a Solaris server where I do not have root. Samtools depends on zlib. The system zlib on this machine is not compiled with large file support, so compiling samtools against this version has the expected effect: samtools only handle small files. I need it to be able to handle large files. Luckily, there is a version of zlib compiled by the admin in /usr/local/apps/zlib-1.2.5/ with large file support. I can compile against this by adding -R /usr/local/apps/zlib-1.2.5/lib to CFLAGS, but this seems not to work. The symptoms are as follows:

When I try to run samtools, it crashes with this error:

ld.so.1: samtools: fatal: relocation error: file samtools: symbol gzopen64: referenced symbol not found

If I add /usr/local/apps/zlib-1.2.5/ to LD_LIBRARY_PATH, then samtools works fine.

Analyzing samtools with ldd and readelf yields the following:

$ ldd -r samtools
        libnsl.so.1 =>   /usr/lib/libnsl.so.1
        libsocket.so.1 =>        /usr/lib/libsocket.so.1
        libresolv.so.2 =>        /usr/lib/libresolv.so.2
        libm.so.2 =>     /usr/lib/libm.so.2
        libcurses.so.1 =>        /usr/lib/libcurses.so.1
        libz.so =>       /usr/lib/libz.so
        libc.so.1 =>     /usr/lib/libc.so.1
        libmp.so.2 =>    /usr/lib/libmp.so.2
        libmd.so.1 =>    /usr/lib/libmd.so.1
        libscf.so.1 =>   /usr/lib/libscf.so.1
        libdoor.so.1 =>  /usr/lib/libdoor.so.1
        libuutil.so.1 =>         /usr/lib/libuutil.so.1
        libgen.so.1 =>   /usr/lib/libgen.so.1
        symbol not found: gzopen64      开发者_运维知识库        (samtools)

$ ldd -s samtools

   ...(snip)...

   find object=libz.so; required by samtools
    search path=/usr/lib:/usr/openwin/lib:/usr/dt/lib:/usr/local/lib  (LD_LIBRARY_PATH)
    trying path=/usr/lib/libz.so
        libz.so =>       /usr/lib/libz.so

   ...(snip)...

$ readelf -d samtools | grep RPATH
 0x0000000f (RPATH)                      Library rpath: [/usr/local/apps/zlib-1.2.5/lib:/usr/local/apps/gcc-4.5.1/lib]

So /usr/local/apps/zlib-1.2.5/lib is clearly in the binary's RPATH, which I understand is supposed to be searched at runtime for shared libraries. However, ldd -s shows that this directory is never searched. Adding this path to LD_LIBRARY_PATH and re-running the ldd commands has the expected effect: the directory is searched and the correct version of libz is found.

So how can I force samtools to search in /usr/local/apps/zlib-1.2.5/lib at runtime without using LD_LIBRARY_PATH?

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Edit: The documentation here would seem to indicate that the -R option is the correct thing to do. But it doesn't work.

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I'm by no means a Solaris expert, but this line:

find object=libz.so; required by samtools
 search path=/usr/lib:/usr/openwin/lib:/usr/dt/lib:/usr/local/lib  (LD_LIBRARY_PATH)

seems to indicate to me that LD_LIBRARY_PATH is already set, and the /usr/lib path in it is taking precedence over any runtime linker paths. Can you unset LD_LIBRARY_PATH if it is in fact present and see if that resolves it?