On Thu, 5 Dec 2019 03:20:19 -0500
Jeffrey Walton <noloa...@gmail.com> wrote:
> On Thu, Dec 5, 2019 at 3:08 AM Niels Möller <ni...@lysator.liu.se> wrote:
> > ...
> >
> > Does OpenBSBs runtime linker look in /usr/local/lib by default? The
> > configure script also supports --with-lib-path=/usr/local/lib, which
> > will add a -L flag and in addition attempt to guess the proper
> > -R/-Wl,-rpath flags.
>
> The runtime linker is configured to use /usr/local/lib. However,
> compile and link requires explicit -I /usr/local/include and -L
> /usr/local/lib to find things.
>
> (Based on my testing of DragonFly, FreeBSD, OpenBSD and NetBSD. I
> don't recall what Debian's kFreeBSD does).
>
> Jeff
Each BSD has its own runtime linker. I believe that OpenBSD ld.so(1)
looks in /usr/local/lib by default, but NetBSD ld.elf_so(1) doesn't
look there.
For OpenBSD, ldconfig(8) sets the runtime path. It always looks in
/usr/lib, but /etc/rc tells ldconfig to also look in /usr/X11R6/lib
and /usr/local/lib. I can get the path from ldconfig:
# OpenBSD
$ ldconfig -r | grep directories
search directories: /usr/lib:/usr/X11R6/lib:/usr/local/lib
NetBSD allows /etc/ld.so.conf to add directories to the runtime path,
but my NetBSD install has no ld.so.conf, so the default path has only
/usr/lib. Some executables have RPATH to look in /usr/X11R7/lib or
/usr/pkg/lib. (My install has no /usr/local.)
For example, OpenBSD's xterm(1) doesn't need RPATH, but NetBSD's
xterm(1) needs RPATH with /usr/X11R7/lib.
# OpenBSD
$ readelf -d /usr/X11R6/bin/xterm | grep -E 'NEED|PATH'
0x00000001 (NEEDED) Shared library: [libXaw.so.15.0]
0x00000001 (NEEDED) Shared library: [libXpm.so.9.0]
0x00000001 (NEEDED) Shared library: [libXt.so.11.0]
...
0x00000001 (NEEDED) Shared library: [libc.so.96.0]
# NetBSD
$ readelf -d /usr/X11R7/bin/xterm | grep -E 'NEED|PATH'
0x00000001 (NEEDED) Shared library: [libXft.so.3]
0x00000001 (NEEDED) Shared library: [libfontconfig.so.2]
0x00000001 (NEEDED) Shared library: [libfreetype.so.18]
...
0x00000001 (NEEDED) Shared library: [libc.so.12]
0x0000000f (RPATH) Library rpath: [/usr/X11R7/lib]
If I don't set RPATH, I can't use /usr/X11R7/lib in NetBSD:
# OpenBSD
$ gcc -o code code.c -L/usr/X11R6/lib -lX11
...
$ ./code
It works!
# NetBSD
$ gcc -o code code.c -L/usr/X11R7/lib -lX11
$ ./code
Shared object "libX11.so.7" not found
$ gcc -o code code.c -L/usr/X11R7/lib -lX11 -R/usr/X11R7/lib
$ ./code
It works!
The NEEDED values on OpenBSD have an extra number: [libc.so.96.0]
instead of just [libc.so.96]. This is because OpenBSD has its different
version rule.
Other systems require M == X in
SONAME libwhat.so.M for NEEDED libwhat.so.X
OpenBSD requires M == X && N >= Y in
SONAME libwhat.so.M.N for NEEDED libwhat.so.X.Y
https://www.openbsd.org/faq/ports/specialtopics.html#SharedLibs
Other systems have symbolic links:
# NetBSD
$ cd /usr/X11R7/lib
$ ls -l libX11.so*
lrwxr-xr-x 1 root wheel 13 Jul 17 2018 libX11.so -> libX11.so.7.0
lrwxr-xr-x 1 root wheel 13 Jul 17 2018 libX11.so.7 -> libX11.so.7.0
-r--r--r-- 1 root wheel 1273908 Jul 17 2018 libX11.so.7.0
OpenBSD doesn't have these links. The compile-time ld(1) and run-time
ld.so(1) look for libraries named [libwhat.so.X.Y].
Nettle doesn't know OpenBSD's version rule. My git checkout of Nettle,
configured for OpenBSD, wants to install [libnettle.so.7.0] with
symlinks from [libnettle.so] and [libnettle.so.7], where the SONAME is
[libnettle.so.7]. To obey the version rule, it should install
[libnettle.so.7.0] without symlinks, and the SONAME should also be
[libnettle.so.7.0]. I didn't fix my git checkout to obey the version
rule, because I didn't need to.
I know one other quirk: some build tools (but not Nettle's) use
$ORIGIN in the runtime path. DragonFly and OpenBSD need a compiler
flag "cc -Wl,-z,origin" to enable $ORIGIN, but other systems don't
need this flag.
https://github.com/mesonbuild/meson/pull/3530/files
This mail is too long; I stop now. --George
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