NAME

       dh_builtusing - set dpkg-gencontrol substitution variables for the Built-Using field

SYNOPSIS

       dh_builtusing [debhelper options] [-c control]

DESCRIPTION

       The dh_builtusing tool belongs to the debhelper collection.  It defines dpkg-gencontrol
       substitutions variables useful in the Built-Using fields of the control file.

       Each item in such fields is the source package of a build dependency, with an exact (=)
       restriction to the version used during the build.  This version is not known in advance,
       and must be passed to dpkg-gencontrol via substitution variables.

       dh_builtusing searches the Built-Using or Static-Built-Using fields of each binary package
       in the source control file for substitution of variables named dh-builtusing:pattern,
       looks for pattern in the Build-Depends fields, deduces the source package and version,
       then defines the variable accordingly in debian/package.substvars.

       It is enabled when the Build-Depends field, or a more specific Build-Depends-Arch or
       Build-Depends-Indep variant, mentions the dh-sequence-builtusing virtual package.

OPTIONS

       Common debhelper command line options and environment variables are recognized.  In
       particular, dh_builtusing only defines variables for the packages selected by options like
       -a, -I and -p.

       -c control
           Read control instead of debian/control.

PATTERN SYNTAX

   Character encoding
       In order to ensure a one-to-one correspondence between dependency names and substitution
       variables, the dot chararcter (.) and the plus character (+) characters are respectively
       encoded as D and P.

       For example, the dh-builtusing:gPP variable refers to the g++ dependency.

   Architecture suffix
       The variable name may carry an architecture suffix, with the same meaning as in Build-
       Depends.

       For example, the dh-builtusing:libc6:amd64 variable may be used to disambiguate
       coinstallable variants.

   Wildcards
       It may not be convenient that the variable name in Built-Using duplicates the full name in
       Build-Depends.  For example, when the name contains a version, the maintainer may not want
       to manually update both fields.

       For such situations, the S character is allowed in pattern, and matches any sequence of
       characters in the name of a build-dependency, like the star character (*) in glob patterns
       or the .* regular expressions.

       The wildcard may select multiple installed packages, but an error is reported if there is
       no match at all.

       For example, the dh-builtusing:gcc-S-source variable may refer to either gcc-12-source, or
       gcc-13-source, or both.

ARCHITECTURE AND PROFILE RESTRICTIONS

       A dependency may be disabled by architecture or build profile restrictions, in which case
       the version does not matter, or can even not be computed if the dependency is not
       installed.  However, the expansion must result in a syntactically valid control file.

       If an architecture or build profile restriction follows a detected variable substitution
       and is not satisfied in the current context, dh_builtusing sets the variable to disabled-
       by-restriction (= 0).

       For example, ${dh-builtusing:libc6} [amd64] expands as libc6 (= VERSION) [amd64] when the
       host architecture matches, else as disabled-by-restriction (= 0) [amd64].

DEBHELPER INTEGRATION

   DH SEQUENCER
       The details described here should rarely be needed.

       The dh-sequence-builtusing virtual package in the Build-Depends field (or a variant) is
       equivalent to the dh-builtusing concrete package, except that the --with=builtusing option
       is implicitly passed to dh.

       The --with=builtusing option has the same effect than an execute_before_dh_gencontrol
       target invoking dh_builtusing.

       When debugging, it may be convenient to define an override_dh_builtusing target invoking
       dh_builtusing with the -v option.

   OTHER DEBHELPER TOOLS
       This part is only of interest for writers of other debhelper tools.

       Other debhelper tools define variables for the Built-Using field, that may refer to
       dependencies not explicitly listed in the Build-Depends field.  So that such tools may
       delegate the computation of the source version, dh_builtusing

       •   reads debian/package.substvars files, in addition to the main control file.

       •   searches all installed packages when no explicit build dependency is found.

       For example, dh_sphinxdoc may define sphinxdoc:Built-Using as
       dh-builtusing:libjs-sphinxdoc.

BUGS AND LIMITATIONS

       Optional assignments in substvars files (?=) are treated as normal assignments.

       When a Build-Depends field contains an alternative (|), both options may match.

EXAMPLE

       If debian/control contains

         Source: foo
         Build-Depends-Arch: dh-sequence-builtusing, gcc-12-source

         Package: bar
         Architecture: any
         Built-Using: ${dh-builtusing:gcc-S-source}

       then the dependency on dh-sequence-builtusing has the same effect than this construct in
       debian/rules.

         gcc_major = ...
         format = $${source:Package} (= $${source:Version})
         value != dpkg-query -Wf'$(format)' gcc-$(gcc_major)-source
         override_dh_gencontrol-arch:
               dh_gencontrol -a -- -Vdh-builtusing:gcc-S-source='$(value)'

SEE ALSO

       debhelper(7), dh_gencontrol(1), deb-substvars(5)

AUTHOR

       Nicolas Boulenguez <nicolas@debian.org>