Syntax

-Wl,-a,{archivesharedshared_archivearchive_shareddefault}

where,

 

-Wl,-a,archive

Selects archive libraries. If the archive library does not exist,

 

the linker generates a warning message and does not create the

 

output file.

-Wl,-a,archive_shared

If archive_shared is active, the archive form is preferred,

 

but the shared form is allowed.

-Wl,-a,shared

Selects shared libraries. If shared libraries do not exist, the

 

linker generates a warning message and does not create the

 

output file.

-Wl,-a,shared_archive

If shared_archive is active, the shared form is preferred, but

 

the archive form is allowed.

-Wl,-a,default

Selects the shared library. If the shared library does not exist,

 

the linker selects the archive library.

Example

The following example directs the linker to use the archive version of the library libshape, followed by standard shared libraries if they exist; otherwise select archive versions.

aCC box.o sphere.o -Wl,-a,archive -lshape -Wl,-a,default

Updating a Shared Library

The aCC command cannot replace or delete object modules in a shared library. To update a C++ shared library, you must recreate the library with all the object files you want the library to include.

For example, when a module in an existing shared library requires a fix, recompile the fixed module with the +z or +Z option, and recreate the shared library with the -boption.

Programs that use this library will now use the new versions of the routines. You do not have to relink programs that use this shared library because they are attached at run time.

Advanced Shared Library Features

This section explains additional things you can perform with shared libraries. It discusses the following topics:

•Forcing the Export of Symbols in main

•Binding Times

•Side Effects of C++ Shared Libraries

•Routines and Options to Manage C++ Shared Libraries

•Version Control for Shared Libraries

•Adding New Versions to a Shared Library

Forcing the Export of Symbols in main

By default, the linker exports from a program only those symbols that were imported by a shared library. For example, if shared libraries of an executable does not reference the main routine of the program, the linker does not include the main symbol in the export list of a.out.

Normally, this is a problem only when a program explicitly calls shared library management routines. (See “Routines and Options to Manage C++ Shared Libraries” (page 183).)

To make the linker export all symbols from a program, use the -Wl,-Eoption, which passes the -Eoption to the linker.

182 Tools and Libraries