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OpenSolaris 2009.06 - man page for ldd (opensolaris section 1)

ldd(1)					  User Commands 				   ldd(1)

       ldd - list dynamic dependencies of executable files or shared objects

       ldd [-d | -r] [-c] [-e envar] [-f] [-i] [-L] [-l] [-p] [-s]
	   [-U | -u] [-v] [-w] filename...

       The  ldd utility lists the dynamic dependencies of executable files or shared objects. ldd
       uses the runtime linker, ld.so.1, to generate the diagnostics. The  runtime  linker  takes
       the object being inspected and prepares the object as would occur in a running process. By
       default, ldd triggers the loading of any lazy dependencies.

       ldd lists the path names of all shared objects that  would  be  loaded  when  filename  is
       loaded.	ldd  expects  the shared objects that are being inspected to have execute permis-
       sion. If a shared object does not have execute permission, ldd  issues  a  warning  before
       attempting to process the file.

       ldd processes its input one file at a time. For each file, ldd performs one of the follow-

	   o	  Lists the object dependencies if the dependencies exist.

	   o	  Succeeds quietly if dependencies do not exist.

	   o	  Prints an error message if processing fails.

       The dynamic objects that are inspected by ldd are not executed. Therefore,  ldd	does  not
       list  any  shared objects explicitly attached using dlopen(3C). To display all the objects
       in use by a process, or a core file, use pldd(1).

       ldd can also check the compatibility of filename with the shared  objects  filename  uses.
       With  the following options, ldd prints warnings for any unresolved symbol references that
       would occur when filename is loaded.

       -d    Check immediate references.

       -r    Check both immediate references and lazy references.

       Only one of the options -d or -r can be specified during any single invocation of ldd.

       immediate references are typically to data items used by the executable or  shared  object
       code.  immediate  references  are  also pointers to functions, and even calls to functions
       made from a position dependent shared object.  lazy  references	are  typically	calls  to
       global  functions  made	from  a  position independent shared object, or calls to external
       functions made from an executable. For more information on these types of  reference,  see
       When  Relocations Are Performed in the Linker and Libraries Guide. Object loading can also
       be affected by relocation processing. See Lazy Loading under USAGE for more details.

       Some unresolved symbol references are not reported by default. These unresolved references
       can  be	reported  with the following options. These options are only useful when combined
       with either the -d or the -r options.

       -p    Expose any unresolved symbol errors to explicit parent and external references.

       -w    Expose any unresolved weak symbol references.

       A shared object can make reference to symbols that should be supplied by the caller of the
       shared  object.	These  references  can be explicitly classified when the shared object is
       created, as being available from a parent, or simply as being external. See the -M mapfile
       option  of  ld(1),  and the PARENT and EXTERN symbol definition keywords. When examining a
       dynamic executable, a parent or external reference that can not be resolved is flagged  as
       an  error. However by default, when examining a shared object, a parent or external refer-
       ence that can not be resolved is not flagged as an error. The -p option,  when  used  with
       either  the  -d	or  -r	options, causes any unresolved parent or external reference to be
       flagged as a relocation error.

       Symbols that are used by relocations may be defined as weak references. By default,  if	a
       weak symbol reference can not be resolved, the relocation is ignored and a zero written to
       the relocation offset. The -w option, when used with either the	-d  or	the  -r  options,
       causes  any unresolved relocation against a weak symbol reference to be flagged as a relo-
       cation error.

       ldd can also check dependency use. With each of the following options, ldd prints warnings
       for any unreferenced, or unused dependencies that are loaded when filename is loaded. Only
       when a symbol reference is bound to a dependency, is that dependency  deemed  used.  These
       options	are  therefore	only  useful  when symbol references are being checked. If the -r
       option is not in effect, the -d option is enabled.

       A dependency that is defined by an object but is not bound  to  from  that  object  is  an
       unreferenced  dependency. A dependency that is not bound to by any other object when file-
       name is loaded is an unused object.

       Dependencies can be located in default system locations, or  in	locations  that  must  be
       specified by search paths. Search paths may be specified globally, such as the environment
       variable LD_LIBRARY_PATH. Search paths can also be defined in dynamic objects as runpaths.
       See  the  -R  option  to ld(1). Search paths that are not used to satisfy any dependencies
       cause unnecessary file system processing.

       -U    Displays any unreferenced, or unused dependencies. If an unreferenced dependency  is
	     not  bound  to by other objects loaded with filename, the dependency is also flagged
	     as unused. Cyclic dependencies that are not bound to from	objects  outside  of  the
	     cycle are also deemed unreferenced.

	     This option also displays any unused search paths.

       -u    Displays any unused objects.

       Only  one  of  the  options -U or -u can be specified during any single invocation of ldd,
       although -U is a superset of -u. Objects that are found to be unreferenced, or unused when
       using  the  -r  option, should be removed as dependencies. These objects provide no refer-
       ences, but result in unnecessary overhead when filename	is  loaded.  When  using  the  -d
       option,	any  objects  that  are  found	to be unreferenced, or unused are not immediately
       required when filename is loaded. These objects are candidates for lazy loading. See  Lazy
       Loading under USAGE for more details.

       The removal of unused dependencies reduces runtime-linking overhead. The removal of unref-
       erenced dependencies reduces runtime-linking overhead to a  lesser  degree.  However,  the
       removal	of  unreferenced  dependencies guards against a dependency being unused when com-
       bined with different objects, or as the other object dependencies evolve.

       The removal of unused search paths can reduce the work required	to  locate  dependencies.
       This  can  be  significant when accessing files from a file server over a network. Note, a
       search path can be encoded within an object to satisfy  the  requirements  of  dlopen(3C).
       This  search  path  might  not  be required to obtain the dependencies of this object, and
       hence will look unused to ldd.

       The following additional options are supported:

       -c	   Disables any configuration file use. Configuration files can  be  employed  to
		   alter  default  search paths, and provide alternative object dependencies. See

       -e envar    Sets the environment variable envar.

		   This option is useful for experimenting with environment  variables	that  are
		   recognized  by  the runtime linker that can adversely affect ldd, for example,

		   This option is also useful for extracting additional information  solely  from
		   the	object	under  inspection,  for  example,  LD_DEBUG.  See  ld.so.1(1) and

       -f	   Forces ldd to check for an executable file that is not  secure.  When  ldd  is
		   invoked by a superuser, by default ldd does not process any executable that is
		   not secure. An executable is not considered secure if the interpreter that the
		   executable specifies does not reside under /lib, /usr/lib or /etc/lib. An exe-
		   cutable is also not considered secure if the interpreter cannot be determined.
		   See Security under USAGE.

       -i	   Displays  the order of execution of initialization sections. The order that is
		   discovered can be affected by use of the -d or -r options. See  Initialization
		   Order under USAGE.

       -L	   Enables  lazy  loading. Lazy loading is the default mode of operation when the
		   object under inspection is loaded as part of a process. In this case, any lazy
		   dependencies,  or  filters, are only loaded into the process when reference is
		   made to a symbol that is defined within the lazy object. The -d or -r options,
		   together  with  the	-L  option,  can be used to inspect the dependencies, and
		   their order of loading as would occur in a running process.

       -l	   Forces the immediate processing of any filters so that all filtees, and  their
		   dependencies,  are  listed.	The  immediate	processing  of filters is now the
		   default mode of operation for ldd. However, under this default  any	auxiliary
		   filtees  that cannot be found are silently ignored. Under the -l option, miss-
		   ing auxiliary filtees generate an error message.

       -s	   Displays the search path used to locate shared object dependencies.

       -v	   Displays all dependency relationships incurred when processing filename.  This
		   option also displays any dependency version requirements. See pvs(1).

       A  superuser should use the -f option only if the executable to be examined is known to be
       trustworthy. The use of -f on an untrustworthy executable while superuser  can  compromise
       system  security.  If an executables trustworthyness is unknown, a superuser should tempo-
       rarily become a regular user. Then invoke ldd as this regular user.

       Untrustworthy objects can be safely examined with dump(1) and with mdb(1), as long as  the
       :r  subcommand  is not used. In addition, a non-superuser can use either the :r subcommand
       of mdb, or truss(1) to examine an untrustworthy executable without too much risk  of  com-
       promise. To minimize risk when using ldd, adb :r, or truss on an untrustworthy executable,
       use the UID "nobody".

   Lazy Loading
       Lazy loading can be applied directly by specified lazy dependencies. See the  -z  lazyload
       option  of  ld(1). Lazy loading can also be applied indirectly through filters. See the -f
       option and -F option of ld(1). Objects that employ lazy loading techniques can  experience
       variations in ldd output due to the options used. If an object expresses all its dependen-
       cies as lazy, the default operation of ldd lists all dependencies in the  order	in  which
       the dependencies are recorded in that object:

	 example% ldd main
		 libelf.so.1 =>   /lib/libelf.so.1
		 libnsl.so.1 =>   /lib/libnsl.so.1
		 libc.so.1 =>	  /lib/libc.so.1

       The  lazy  loading behavior that occurs when this object is used at runtime can be enabled
       using the -L option. In this mode, lazy dependencies are loaded when reference is made  to
       a  symbol  that is defined within the lazy object. Therefore, combining the -L option with
       use of the -d and -r options reveals the dependencies that are needed to satisfy the imme-
       diate, and lazy references respectively:

	 example% ldd -L main
	 example% ldd -d main
		 libc.so.1 =>	    /lib/libc.so.1
	 example% ldd -r main
		 libc.so.1 =>	    /lib/libc.so.1
		 libelf.so.1 =>   /lib/libelf.so.1

       Notice that in this example, the order of the dependencies that are listed is not the same
       as displayed from ldd with no options. Even with the -r	option,  the  lazy  reference  to
       dependencies might not occur in the same order as would occur in a running program.

       Observing lazy loading can also reveal objects that are not required to satisfy any refer-
       ences. These objects, in this example, libnsl.so.1, are candidates for  removal	from  the
       link-line used to build the object being inspected.

   Initialization Order
       Objects that do not explicitly define their required dependencies might observe variations
       in the initialization section order displayed by ldd due to the options used. For example,
       a simple application might reveal:

	 example% ldd -i main
		 libA.so.1 =>	  ./libA.so.1
		 libc.so.1 =>	  /lib/libc.so.1
		 libB.so.1 =>	  ./libB.so.1

	     init object=./libB.so.1
	     init object=./libA.so.1
	     init object=/lib/libc.so.1

       whereas, when relocations are applied, the initialization section order is:

	 example% ldd -ir main

	     init object=/lib/libc.so.1
	     init object=./libB.so.1
	     init object=./libA.so.1

       In  this  case,	libB.so.1  makes  reference to a function in /usr/lib/libc.so.1. However,
       libB.so.1 has no explicit dependency on this library. Only after a relocation  is  discov-
       ered is a dependency then established. This implicit dependency affects the initialization
       section order.

       Typically, the initialization section order established when an application  is	executed,
       is  equivalent to ldd with the -d option. The optimum order can be obtained if all objects
       fully define their dependencies. Use of the ld(1) options -zdefs and -zignore when  build-
       ing dynamic objects is recommended.

       Cyclic  dependencies  can  result  when	one or more dynamic objects reference each other.
       Cyclic dependencies should be avoided, as a unique initialization  sort	order  for  these
       dependencies can not be established.

       Users  that  prefer  a more static analysis of object files can inspect dependencies using
       tools such as dump(1) and elfdump(1).

       /usr/lib/lddstub       Fake 32-bit executable loaded to check the dependencies  of  shared

       /usr/lib/64/lddstub    Fake  64-bit  executable loaded to check the dependencies of shared

       See attributes(5) for descriptions of the following attributes:

       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       |Availability		     |SUNWtoo			   |

       crle(1),  dump(1),  elfdump(1),	lari(1),  ld(1),  ld.so.1(1),  mdb(1),	pldd(1),  pvs(1),
       truss(1), dlopen(3C), attributes(5)

       Linker and Libraries Guide

       ldd  prints  the record of shared object path names to stdout. The optional list of symbol
       resolution problems is printed to stderr. If filename is  not  an  executable  file  or	a
       shared  object,	or  if	filename  cannot be opened for reading, a non-zero exit status is

       Use of the -d or -r option with shared objects can give misleading  results.  ldd  does	a
       worst  case  analysis of the shared objects. However, in practice, the symbols reported as
       unresolved might be resolved by the executable file referencing	the  shared  object.  The
       runtime	linkers  preloading  mechanism	can be employed to add dependencies to the object
       being inspected. See LD_PRELOAD.

       ldd uses the same algorithm as the runtime linker to locate shared objects.

SunOS 5.11				    3 Jun 2008					   ldd(1)

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