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Chapter 8

Shared libraries

Packages containing shared libraries must be constructed with a little care to make sure that

the shared library is always available. This is especially important for packages whose shared

libraries are vitally important, such as the C library (currently

libc6

).

Packages involving shared libraries should be split up into several binary packages. This sec 

tion mostly deals with how this separation is to be accomplished; rules for files within the

shared library packages are in `Libraries' on page

78

instead.

8.1 Run time shared libraries

The run time shared library needs to be placed in a package whose name changes when 

ever the shared object version changes.

1

The most common mechanism is to place it in

a package called

librarynamesoversion

, where

soversion

is the version number in

the soname of the shared library

2

. Alternatively, if it would be confusing to directly ap 

pend soversion to libraryname (e.g. because libraryname itself ends in a number), you may use

libraryname

soversion

and

libraryname

soversion

 dev

instead.

If your package includes run time support programs that do not need to be invoked manually

by users, but are nevertheless required for the package to function, then it is recommended that

these programs are placed (if they are binary) in a subdirectory of

/usr/lib

, preferably under

/usr/lib/

package name. If the program is architecture independent, the recommendation is

for it to be placed in a subdirectory of

/usr/share

instead, preferably under

/usr/share

/

package name.

If you have several shared libraries built from the same source tree you may lump them all

together into a single shared library package, provided that you change all of their sonames

1

Since it is common place to install several versions of a package that just provides shared libraries, it is a good

idea that that the library package should not contain any extraneous non versioned files, unless they happen to be

in versioned directories.

2

The soname is the shared object name: it's the thing that has to match exactly between building an executable

and running it for the dynamic linker to be able run the program. For example, if the soname of the library is

libfoo.so.6

, the library package would be called

libfoo6

.