just another - out of thousands - example that shared libraries are one
of the worst thing invented in computing.
Maybe except of single system wide shared library with constant interface.
On Thu, 10 May 2018, Gleb Popov wrote:
On Thu, May 10, 2018 at 2:45 AM, Steve Kargl <
s...@troutmask.apl.washington.edu> wrote:
In review PR 228007, it came to my attention some individuals are
mis-characterizing a FreeBSD loader issue as "gfortran's FreeBSD
issue". See
https://lists.freebsd.org/pipermail/freebsd-fortran/2018-May/000124.html
The problem can be summarized by the following
% gfortran7 -o z h.f90
% ./z
/lib/libgcc_s.so.1: version GCC_4.8.0 required by \
/usr/local/lib/gcc7/libgfortran.so.4 not found
gfortran7 is installed from ports/lang/gcc7. This is not
a "gfortran's FreeBSD issue". This is a FreeBSD loader issue.
Specifically, there is a shared library name clash.
% ldconfig -r | grep gcc_
6:-lgcc_s.1 => /lib/libgcc_s.so.1
716:-lgcc_s.1 => /usr/local/lib/gcc7/libgcc_s.so.1
% ldd z
z:
libgfortran.so.4 => /usr/local/lib/gcc7/libgfortran.so.4 (0x200645000)
libm.so.5 => /lib/libm.so.5 (0x200a17000)
libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x200a4b000)
libquadmath.so.0 => /usr/local/lib/gcc7/libquadmath.so.0 (0x200a63000)
libc.so.7 => /lib/libc.so.7 (0x200ca3000)
So, the runtime loader finds 6 instead of 716, tries to link,
fails, and issues an error message. There are a number ways to
fix this issue.
1) By far, the best solution would be to stop hijacking the libgcc
name in libraries installed on FreeBSD that are not related to
actual GCC software.
% ls -l /lib/libgcc* /usr/lib/libgcc*
(trimming lines)
/lib/libgcc_s.so.1
/usr/lib/libgcc.a@ -> libcompiler_rt.a
/usr/lib/libgcc_eh.a
/usr/lib/libgcc_eh_p.a
/usr/lib/libgcc_p.a@ -> libcompiler_rt_p.a
/usr/lib/libgcc_s.so@ -> ../../lib/libgcc_s.so.1
Why not use libcompiler_rt_s.so.1 (or libclang_s.so.1)? Yes, I'm
aware that clang does not work on all archs and the ancient gcc
lives on.
2) Given the expected push back againt solution 1), this solution
proposes bumping the library version for /lib/libgcc_s.so.1 from
1 to some larger value, say, 10. It is unlikely that GCC will
bump its shared library number anytime soon. GCC bumped it from
0 to 1 some 16 years ago.
https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=43316
This solution, however, papers over the general problem with
name clashes.
3) This solution is to actually fix the runtime loader. If an error
occurs with loading a shared library, then iterate over the entries
in the hints file to check to see if another hint would satisfy
the linking. Here, instead of issuing the above error, the loader
would find entry 716, and load the correct libgcc_s.so.1.
Admittedly, I haven't looked to see how difficult this solution
would be.
4) Bump the shared library number of the individual ports. As a proof
of concept, I've done this with ports/lang/gcc6.
% cat /usr/ports/lang/gcc6/files/patch-t-slibgcc
--- libgcc/config/t-slibgcc.orig 2018-05-08 12:47:42.334495000 -0700
+++ libgcc/config/t-slibgcc 2018-05-08 12:45:26.872312000 -0700
@@ -20,7 +20,7 @@
SHLIB_EXT = .so
SHLIB_SOLINK = @shlib_base_name@.so
-SHLIB_SOVERSION = 1
+SHLIB_SOVERSION = 2
SHLIB_SONAME = @shlib_base_name@.so.$(SHLIB_SOVERSION)
SHLIB_MAP = @shlib_map_file@
SHLIB_OBJS = @shlib_objs@
% ldconfig -r | grep gcc_
6:-lgcc_s.1 => /lib/libgcc_s.so.1
716:-lgcc_s.1 => /usr/local/lib/gcc7/libgcc_s.so.1
766:-lgcc_s.2 => /usr/local/lib/gcc6/libgcc_s.so.2
% gfortran6 -o z h.f90
% ./z
hello
% ldd z
z:
libgfortran.so.3 => /usr/local/lib/gcc6/libgfortran.so.3 (0x200645000)
libm.so.5 => /lib/libm.so.5 (0x20096c000)
libgcc_s.so.2 => /usr/local/lib/gcc6/libgcc_s.so.2 (0x2009a0000)
libquadmath.so.0 => /usr/local/lib/gcc7/libquadmath.so.0 (0x200bb7000)
libc.so.7 => /lib/libc.so.7 (0x200df7000)
This works for this particular name conflict. Hopefully, FreeBSD
never needs to bump /lib/libgcc_s.so.1 to /lib/libgcc_s.so.2. This,
however, introduces an incompatibility with what is actually distributed
by GCC.
Finally, can people stop referring to the above error as
"gfortran's FreeBSD issue". This is a FreeBSD runtime loader issue.
Our libgcc also lacks some functionality compared to the original one:
https://reviews.freebsd.org/D11482
--
Steve
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