Gcc linker search path order Post: 302903056

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Top Forums Programming Gcc linker search path order Post 302903056 by Richard Johnson on Friday 23rd of May 2014 04:40:30 PM

05-23-2014

Registered User

Gcc linker search path order

I have a build where I wish to link against and load a specific version of a library and a different version of the same library is installed on the system. I'm using a -L option to point to the version that I wish to link against but gcc still seems to choose the installed version. Is there a way to force gcc to search the directory specified with the -L option before it searches the standard locations?

I'm running Centos 6.5 with gcc 4.4.7. Here are the relevant libs and directories, zlib-devel is not installed

Code:

/lib64/libz.so.1.2.3
/lib64/libz.so.1 -> libz.so.1.2.3
 
/home/richj/product/zlib/lib/libz.so.1.2.8
/home/richj/product/zlib/lib/libz.so -> libz.so.1.2.8
/home/richj/product/zlib/lib/libz.so.1 -> libz.so.1.2.8
/home/richj/product/zlib/include/zlib.h
 
/home/richj/product/foo/libfoo.so
/home/richj/product/foo/foo.h
 
/home/richj/product/bar/bar.c

Main in bar.c calls foo in libfoo.so and foo calls inflateInit in libz Here are the compile commands for libfoo.so and bar. Both the library and the program compile and run without error.

Code:

/usr/bin/gcc -c -fPIC -Wall -g -I../zlib/include foo.c
/usr/bin/gcc -shared -o libfoo.so foo.o
 
/usr/bin/gcc -Wall -g -I../foo -L../foo -lfoo -L../zlib/lib -lz bar.c -o bar
 
$ldd bar
linux-vdso.so.1 => (0x00007fffd67ff000)
libfoo.so => ../foo/libfoo.so
libz.so.1 => /lib64/libz.so.1
libc.so.6 => /lib64/libc.so.6
/lib64/ld-linux-x86-64.so.2

So the question is why is it not linking against and loading the version of zlib that I point to in the compile command?

Last edited by Scott; 05-23-2014 at 06:09 PM.. Reason: Please use code tags

Richard Johnson

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LEARN ABOUT LINUX

dh_shlibdeps

DH_SHLIBDEPS(1) 						     Debhelper							   DH_SHLIBDEPS(1)

NAME

       dh_shlibdeps - calculate shared library dependencies

SYNOPSIS

       dh_shlibdeps [debhelperoptions] [-Lpackage] [-ldirectory] [-Xitem] [--params]

DESCRIPTION

       dh_shlibdeps is a debhelper program that is responsible for calculating shared library dependencies for packages.

       This program is merely a wrapper around dpkg-shlibdeps(1) that calls it once for each package listed in the control file, passing it a list
       of ELF executables and shared libraries it has found.

OPTIONS

       -Xitem, --exclude=item
	   Exclude files that contain item anywhere in their filename from being passed to dpkg-shlibdeps. This will make their dependencies be
	   ignored.  This may be useful in some situations, but use it with caution. This option may be used more than once to exclude more than
	   one thing.

       -- params
	   Pass params to dpkg-shlibdeps(1).

       -uparams, --dpkg-shlibdeps-params=params
	   This is another way to pass params to dpkg-shlibdeps(1).  It is deprecated; use -- instead.

       -ldirectory[:directory ...]
	   With recent versions of dpkg-shlibdeps, this option is generally not needed.

	   Before dpkg-shlibdeps is run, LD_LIBRARY_PATH will have added to it the specified directory (or directories -- separate with colons).
	   With recent versions of dpkg-shlibdeps, this is mostly only useful for packages that build multiple flavors of the same library, or
	   other situations where the library is installed into a directory not on the regular library search path.

       -Lpackage, --libpackage=package
	   With recent versions of dpkg-shlibdeps, this option is generally not needed, unless your package builds multiple flavors of the same
	   library.

	   It tells dpkg-shlibdeps (via its -S parameter) to look first in the package build directory for the specified package, when searching
	   for libraries, symbol files, and shlibs files.

EXAMPLES

       Suppose that your source package produces libfoo1, libfoo-dev, and libfoo-bin binary packages. libfoo-bin links against libfoo1, and should
       depend on it. In your rules file, first run dh_makeshlibs, then dh_shlibdeps:

	       dh_makeshlibs
	       dh_shlibdeps

       This will have the effect of generating automatically a shlibs file for libfoo1, and using that file and the libfoo1 library in the
       debian/libfoo1/usr/lib directory to calculate shared library dependency information.

       If a libbar1 package is also produced, that is an alternate build of libfoo, and is installed into /usr/lib/bar/, you can make libfoo-bin
       depend on libbar1 as follows:

	       dh_shlibdeps -Llibbar1 -l/usr/lib/bar

SEE ALSO

       debhelper(7), dpkg-shlibdeps(1)

       This program is a part of debhelper.

AUTHOR

       Joey Hess <joeyh@debian.org>

8.9.0ubuntu2.1							    2012-06-12							   DH_SHLIBDEPS(1)