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Linker and Libraries Guide     Oracle Solaris 11 Express 11/10
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Document Information


1.  Introduction to the Oracle Solaris Link Editors

2.  Link-Editor

3.  Runtime Linker

4.  Shared Objects

Naming Conventions

Recording a Shared Object Name

Inclusion of Shared Objects in Archives

Recorded Name Conflicts

Shared Objects With Dependencies

Dependency Ordering

Shared Objects as Filters

Generating Standard Filters

Generating Auxiliary Filters

Filtering Combinations

Filtee Processing

Performance Considerations

Analyzing Files With elfdump

Underlying System

Lazy Loading of Dynamic Dependencies

Position-Independent Code

SPARC: -K pic and -K PIC Options

Remove Unused Material

Maximizing Shareability

Move Read-Only Data to Text

Collapse Multiply-Defined Data

Use Automatic Variables

Allocate Buffers Dynamically

Minimizing Paging Activity


Symbol Lookup

When Relocations are Performed

Combined Relocation Sections

Copy Relocations

Using the -B symbolic Option

Profiling Shared Objects

5.  Application Binary Interfaces and Versioning

6.  Support Interfaces

7.  Object File Format

8.  Thread-Local Storage

9.  Mapfiles

A.  Link-Editor Quick Reference

B.  Versioning Quick Reference

C.  Establishing Dependencies with Dynamic String Tokens

D.  Direct Bindings

E.  System V Release 4 (Version 1) Mapfiles

F.  Linker and Libraries Updates and New Features


Shared Objects With Dependencies

Shared objects can have their own dependencies. The search rules used by the runtime linker to locate shared object dependencies are covered in Directories Searched by the Runtime Linker. If a shared object does not reside in one of the default search directories, then the runtime linker must explicitly be told where to look. For 32–bit objects, the default search directories are /lib and /usr/lib. For 64–bit objects, the default search directories are /lib/64 and /usr/lib/64. The preferred mechanism of indicating the requirement of a non-default search path, is to record a runpath in the object that has the dependencies. A runpath can be recorded by using the link-editor's -R option.

In the following example, the shared object has a dependency on, which is expected to reside in the directory /home/me/lib at runtime or, failing that, in the default location.

$ cc -o -G -K pic bar.c
$ cc -o -G -K pic foo.c -R/home/me/lib -L. -lbar
$ elfdump -d | egrep "NEEDED|RUNPATH"
       [1]  NEEDED        0x123
       [2]  RUNPATH       0x456         /home/me/lib

The shared object is responsible for specifying all runpaths required to locate its dependencies. Any runpaths specified in the dynamic executable are only used to locate the dependencies of the dynamic executable. These runpaths are not used to locate any dependencies of the shared objects.

The LD_LIBRARY_PATH family of environment variables have a more global scope. Any path names specified using these variables are used by the runtime linker to search for any shared object dependencies. Although useful as a temporary mechanism that influences the runtime linker's search path, the use of these environment variables is strongly discouraged in production software. See Directories Searched by the Runtime Linker for a more extensive discussion.