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.\" $OpenBSD: library-specs.7,v 1.13 2018/07/09 15:34:10 jmc Exp $
.\"
.\" Copyright (c) 2001-2010 Marc Espie
.\"
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd $Mdocdate: July 9 2018 $
.Dt LIBRARY-SPECS 7
.Os
.Sh NAME
.Nm library-specs
.Nd shared library name specifications
.Sh DESCRIPTION
Each
.Ev WANTLIB
item in the ports tree conforms to
.Bd -literal -offset indent
[path/]libname[=major[.minor]]
.Ed
.Pp
or
.Bd -literal -offset indent
[path/]libname[>=major[.minor]]
.Ed
.Pp
All libraries that a package needs must be mentioned in that list.
Except for system and X11 libraries, they all must be reachable through
.Ev LIB_DEPENDS
and
.Ev RUN_DEPENDS ,
directly, or indirectly through recursive dependencies.
.Pp
Conversely, the ports tree
uses
.Ev WANTLIB
to check whether a given
.Ev LIB_DEPENDS
will be required at runtime for shared libraries, and thus turn it into a
.Cm @depend
line
.Po
see
.Xr pkg_create 1
.Pc .
.Pp
The package system will embed correct dependency checks in the built
package in the form of
.Cm @wantlib
lines, according to the normal shared library semantics: any library with
the same major number, and a greater or equal minor number will do.
.Pp
Note that static libraries can only satisfy a library specification if
no shared library has been found.
Thus, if WANTLIB = foo>=5, and both libfoo.so.4.0 and libfoo.a are present,
the check will fail.
.Pp
Therefore, porters must strive to respect correct shared library semantics
in their own ports: by bumping the minor number each time the interface is
augmented, and by bumping the major number each time the interface changes.
Note that adding functions to a library is an interface augmentation.
Removing functions is an interface change.
.Pp
The major.minor components of the library specification are used only as a
build-time check, the run-time checks are computed by
.Xr port-resolve-lib-helper 1 .
For
.Sq libname>=major[.minor] ,
any library which is more recent than the given major.minor version will
do.
If a specific major number is needed, use the form
.Sq libname=major[.minor] .
If the minor component is left empty, any minor will do.
If both components are left empty, any version will do.
.Pp
Most specifications won't mention a
.Pa path :
.Xr port-resolve-lib-helper 1
will look in the default
.Xr ldconfig 8
path automatically, namely
.Pa /usr/local/lib ,
.Pa /usr/X11R6/lib ,
.Pa /usr/lib .
It is generally a bad idea to put libraries elsewhere as they won't be
reached directly.
.Pp
However, distinct ports may install different major versions of the same
library in
.Pa /usr/local/lib ,
and disambiguate the build by creating a link in a separate directory,
and specifying the right options to the linker.
.Pp
These libraries will require a
.Pa path
component in the corresponding
.Ev WANTLIB
to make sure the right library is resolved.
This path is rooted under
.Pa /usr/local .
For instance, to refer to
.Pa /usr/local/lib/qt3/libqt-mt.so.33.0 ,
one would use
.Sq lib/qt3/qt-mt>=33 .
.Sh SEE ALSO
.Xr check-lib-depends 1 ,
.Xr ld 1 ,
.Xr ld.so 1 ,
.Xr pkg_add 1 ,
.Xr port-resolve-lib-helper 1 ,
.Xr bsd.port.mk 5 ,
.Xr packages 7 ,
.Xr packages-specs 7 ,
.Xr ports 7 ,
.Xr ldconfig 8
.Sh HISTORY
Full support for library specifications first appeared in
.Ox 3.1 .
The format of specifications changed slightly to include
.Sq >=
before
.Ox 4.0 .
The interactions between
.Ev LIB_DEPENDS
and
.Ev WANTLIB
were modified and clarified for
.Ox 4.8 .
The format of specifications changed again before
.Ox 4.9
to remove extra noise.
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