Chapter 8. Shared libraries

58

Otherwise, you will need to explicitly list the compiled binaries and libraries.

8

This command puts the dependency information into the

debian/substvars

file, which is

then used by

dpkg gencontrol

. You will need to place a

${shlib:Depends}

variable in

the

Depends

field in the control file for this to work.

If

dpkg shlibdeps

doesn't complain, you're done. If it does complain you might need to

create your own

debian/shlibs.local

file, as explained below (see `Writing the

debian

/shlibs.local

file' on the next page).

If you have multiple binary packages, you will need to call

dpkg shlibdeps

on each one

which contains compiled libraries or binaries. In such a case, you will need to use the

 T

option to the

dpkg

utilities to specify a different

substvars

file.

For more details on dpkg shlibdeps, please see `

dpkg shlibdeps

  calculates shared library

dependencies' on page

113

and

dpkg shlibdeps(1)

.

8.6.3 The

shlibs

File Format

Each

shlibs

file has the same format. Lines beginning with

#

are considered to be comments

and are ignored. Each line is of the form:

library name soname version number dependencies ...

We will explain this by reference to the example of the

zlib1g

package, which (at the time of

writing) installs the shared library

/usr/lib/libz.so.1.1.3

.

library name is the name of the shared library, in this case

libz

. (This must match the name

part of the soname, see below.)

soname version number is the version part of the soname of the library. The soname is the thing

that must exactly match for the library to be recognized by the dynamic linker, and is usually

of the form

name

.so.

major version

, in our example,

libz.so.1

.

9

The version part is the

part which comes after

.so.

, so in our case, it is

1

.

dependencies has the same syntax as a dependency field in a binary package control file. It

should give details of which packages are required to satisfy a binary built against the version

of the library contained in the package. See `Syntax of relationship fields' on page

45

for details.

In our example, if the first version of the

zlib1g

package which contained a minor number of

at least

1.3

was 1:1.1.3 1, then the

shlibs

entry for this library could say:

libz 1 zlib1g (>= 1:1.1.3)

The version specific dependency is to avoid warnings from the dynamic linker about using

older shared libraries with newer binaries.

8

If you are using

debhelper

, the

dh_shlibdeps

program will do this work for you. It will also correctly

handle multi binary packages.

9

This can be determined using the command

objdump  p /usr/lib/libz.so.1.1.3 | grep SONAME