Provided by: dh-ada-library_9.9_all 
NAME
dh_ada_library - help packaging Ada libraries for Debian
SYNOPSIS
dh_ada_library [debhelper options]
DESCRIPTION
dh_ada_library is a debhelper program that handles some common tasks in packaging libraries written in
the Ada programming language.
The difficult work is to convince the upstream build system to produce both a static and a relocatable
library in a row (during the dh_auto_configure and dh_auto_build steps), then to install these under
debian/tmp/ with the directory structure described by the Debian Policy for Ada (dh_auto_install). The
/usr/share/ada/packaging.mk Makefile snippet, part of the same dh-ada-library package, may help for that.
It contains lots of comments describing its usage.
Once the files are installed, dh_ada_library is in charge of dispatching them to the specific package
temporary directories. It is enabled by the presence of the dh-sequence-ada-library virtual package in
the Build-Depends-Arch field of the debian/control file. For a while, you should in addition depend on
the explicit dh-ada-library concrete package and require at least version 9, because this version
introduces incompatible changes, and virtual packages cannot receive version restrictions.
At start, it parses debian/control to find Ada libraries: architecture-dependent packages, named
libname-dev, depending on ${ada:Depends} and providing ${ada:Provides}.
For each one, there must also be a runtime library package, named from the shared object name as
described in section 8 of the Debian Policy (usually libname-SOversion).
For a description of DEB_HOST_MULTIARCH, see dpkg-architecture(1). The installation directories
(DEB_ADA_SOURCE_DIR, DEB_LIB_DIR, DEB_ADA_LIB_INFO_DIR and DEB_GNAT_PROJECT_DIR) are defined in the
Debian Policy, their current values are available via packaging.mk.
Runtime library package
The following files are copied from debian/tmp/ to debian/libname-SOversion/.
DEB_LIB_DIR/shared library
The concrete file containing the shared library. It is found by following the
debian/tmp/DEB_LIB_DIR/libname.so symbolic link.
DEB_LIB_DIR/SOname
The shared object name (SOname) is extracted from the binary data in the shared library, and may
differ from the file name. If so, this symbolic link also refers to the shared library and is also
installed (for ldconfig, see the Debian Policy for details).
dh_link later removes the redundant path components like lib/...
Versions before 8.1 were ignoring the SOname/Library_Version, and guessing it from the SOversion in the
Debian package name. Patches caused by this unfortunate decision can now be unapplied.
Development package (-dev)
The following files are copied from debian/tmp/ to debian/libname/.
DEB_ADA_LIB_INFO_DIR/name/*.ali
The GNAT Ada Library Information files files created along the objects when building the shared
library.
dh_fixperms later checks that their permissions are 444.
In order to improve build reproducibility, -f*-prefix-map compiler flags are removed from them.
DEB_ADA_SOURCE_DIR/name/*
The sources, Ada or not, should all be in a single directory.
DEB_LIB_DIR/libname.a
The static archive.
DEB_GNAT_PROJECT_DIR/name.gpr
This standalone library GNAT project intended for use after installation.
If the library was built with gprbuild and another GNAT project, the gprinstall tool can generate
such a standalone project with the correct Languages, Linker_Switches in the Linker package, imports
(with), source file renamings... Else, the maintainer must write a new project, or more accurately
generate it because DEB_HOST_MULTIARCH cannot be hardcoded. If so, it is recommended to also
substitute the path variables set by /usr/share/ada/packaging.mk, in case the directory structure
ever has to change (again).
In order to improve build reproducibility, -f*-prefix-map compiler flags are removed (for examples
because gprbuild has copied variables like ADAFLAGS from the build project).
DEB_LIB_DIR/libname.so
The development symbolic link is installed here, but dangling because the concrete shared library is
in the runtime library package.
dh_link later removes the redundant path components like lib/...
ada:Depends
This debhelper substitution variable is created for inclusion in the Depends field of the libname-dev
package in debian/control. Its value contains the following dependencies.
libname-SOversion (= ${binary:Version})
The development package needs the same version of the runtime library package because of the
dangling symbolic link.
gnat (>= DEB_GNAT_VERSION), gnat (<< DEB_GNAT_VERSION + 1)
The development package requires the default Ada compiler in order to ensure the compatibility
with all other Ada packages.
gnat-DEB_GNAT_VERSION-HASH
This virtual package reflects the (host) version of the run-time library used during the build.
More items are added as described in the next sections in order to reflect the dependencies across
Ada library packages.
ada:Provides
This debhelper substitution variable is created for inclusion in the Provides field of the
libname-dev package in debian/control.
It only contains libname-dev-HASH, where HASH is a 32 bit XOR of all checksums in the .ali files (8
lowercase hexadecimal digits).
Imported projects
In addition, dh_ada_library searches debian/tmp/DEB_GNAT_PROJECT_DIR/name.gpr for imported projects
(with). For each imported library project dep.gpr, a dependency is added into ada:Depends.
If libdep-dev is built from the same source package, the dependency is libdep-dev (=
${binary:Version}), ensuring that all static libraries are compiled with compatible options. Such a
restriction is more specific than a hash suffix.
If libdep-dev is not built from the same source but is installed on the system, in other words if it
is listed in Build-Depends, the dependency is on the libdep-dev-hash virtual package provided by the
installed concrete libdep-dev. It prevents later installation of an update of libdep-dev modifying
its ALI checksums.
Remaining projects trigger a warning, because the maintainer will need to find the right dependency.
Versions before 8.1 were guessing more dependencies from Linker'Linker_Options. This was often wrong,
for no benefit since C -dev packages carry no version and can be hard-coded in debian/control.
Files that are not installed
The following files, if they exist under debian/tmp/, are ignored but marked as installed by
dh_ada_library in order to prevent a false alert by dh_missing later, as if the files were listed in
debian/not-installed.
usr/unwantedly_gprinstalled/
Please refer to /usr/share/ada/packaging.mk.
DEB_LIB_DIR/libname.la
The Debian Policy recommends not to install libtool .la files.
REMARKS
It would be easy to fix the directory structure, and versions before 8.1 were doing exactly this, at the
cost of generating a project with different paths. Now that gprinstall is almost capable of dealing with
stagged installs, duplicating its job seems a waste of energy.
For now, DEB_ADA_SOURCE_DIR and DEB_GNAT_PROJECT_DIR are under /usr/share/ada/. This implies that the
-dev package cannot be declared Multi-Arch: same as the content of the project (and maybe of generated
sources) will vary across architectures.
The Linker'Linker_Options attribute should rarely be needed. A dependency written in Ada should be
described by an imported project, also handling .ali files. A dependency written in C should be listed
in Library_Options when building a shared library, and in Linker'Linker_Options when using a static
archive, but is not always required in Linker'Linker_Options for shared libraries. Until now, such
options have only proved useful to light bindings importing C symbols from a specification or an inlined
procedure. In a foo.pc file as read by pkg-config, they are named Libs, excluding -lfoo and
Libs.private.
OPTIONS
Common debhelper command line options and environment variables are recognized.
--export-versions
This option is intended for support of packaging.mk. Print Makefile definitions for the variables
described in it.
EXAMPLES
This stanza in debian/rules may help debugging.
override_dh_ada_library:
dh_ada_library -v"
VERSIONS
The version is composed of two numbers separated by a dot. The second one increases during a normal
update, which supposedly fixes bugs, introduces compatible evolutions, or remove stuff unused since
oldoldstable. A change in the first one announces an incompatibility requiring some users to modify
their source package.
SEE ALSO
debhelper(7), deb-substvars(5), the Debian Policy at
<https://www.debian.org/doc/debian-policy/ch-sharedlibs.html#run-time-shared-libraries>, the Debian
Policy for Ada at <http://people.debian.org/~lbrenta/debian-ada-policy.html>, and the documentation of
GNAT project tools installed into /usr/share/doc/gprbuild by the gprbuild-doc package.
AUTHOR
Nicolas Boulenguez <nicolas@debian.org>
9.9 2025-03-28 DH_ADA_LIBRARY(1)