misc/cgo/testcshared failure, linking to wrong libgo.so

[hartzell]

TL;DR: I needed to change libgo.so to ./libgo.so on one line in test.bash to make misc/cgo/testcshared pass and am looking for feedback.

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

Building 1.7.3 with a go built from release-branch.go1.4

What operating system and processor architecture are you using (go env)?

go env output from the successful build mentioned below:

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH=""
GORACE=""
GOROOT="/rss/spack-20161101/opt/spack/linux-centos7-x86_64/gcc-5.4.0/go-1.7.3-wzhabet756id3kyoqr6v6hnrwopfkpic"
GOTOOLDIR="/rss/spack-20161101/opt/spack/linux-centos7-x86_64/gcc-5.4.0/go-1.7.3-wzhabet756id3kyoqr6v6hnrwopfkpic/pkg/tool/linux_amd64"
CC="/rss/spack-20161101/lib/spack/env/gcc/gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0"
CXX="/rss/spack-20161101/lib/spack/env/gcc/g++"
CGO_ENABLED="1"

I'm working in a DigitalOcean droplet based on their CentOS7 image with a minimal set of packages added. I've worked through the problem described in #16283 by adding the kernel boot flag. I also had to add glibc-static to my "minimal" set of packages so that the cgo static linking tests pass.

What did you do?

I'm updating go packaging in the spack package manager.

I've updated their go-bootstrap package to use release-branch.go1.4 instead of 1.4.2 to pick up Brad's timezone fix. I have not yet submitted a pull request to the spack project for this change (but will).

I'm using that go-bootstrap package to build 1.7.3.

I've updated their go package to include an entry for the 1.7.3 tag.

The testing step has been failing in misc/cgo/testcshared with this message:

./testp: symbol lookup error: ./testp: undefined symbol: DidInitRun

After drilling down into the tests to the point where I was able to build the test itself and replicate the failure, I noticed that testp was linking against the "wrong" libgo.so. When I added a "./" to the shared library name, it linked against the "right" libgo.so the test passed.

[hartzelg@spack-0 testcshared]$ $(go env CC) ${GOGCCFLAGS} -I ${installdir} -o testp main0.c libgo.$libext
[hartzelg@spack-0 testcshared]$ ./testp
./testp: symbol lookup error: ./testp: undefined symbol: DidInitRun
[hartzelg@spack-0 testcshared]$ ldd testp
	linux-vdso.so.1 =>  (0x00007ffcd83c1000)
	libgo.so => /rss/spack-20161101/opt/spack/linux-centos7-x86_64/gcc-4.8.5/gcc-5.4.0-5ugmutg4tsvybv3zsrhfa5h67ltzrc5i/lib64/libgo.so (0x00007fdffe6aa000)
	libpthread.so.0 => /lib64/libpthread.so.0 (0x00007fdffe487000)
	libc.so.6 => /lib64/libc.so.6 (0x00007fdffe0c5000)
	libm.so.6 => /lib64/libm.so.6 (0x00007fdffddc3000)
	libgcc_s.so.1 => /rss/spack-20161101/opt/spack/linux-centos7-x86_64/gcc-4.8.5/gcc-5.4.0-5ugmutg4tsvybv3zsrhfa5h67ltzrc5i/lib64/libgcc_s.so.1 (0x00007fdffdbab000)
	/lib64/ld-linux-x86-64.so.2 (0x00007fdfff8ea000)
[hartzelg@spack-0 testcshared]$ pwd
/rss/spack-20161101/var/spack/stage/go-1.7.3-wzhabet756id3kyoqr6v6hnrwopfkpic/go/misc/cgo/testcshared
[hartzelg@spack-0 testcshared]$ $(go env CC) ${GOGCCFLAGS} -I ${installdir} -o testp main0.c ./libgo.$libext
[hartzelg@spack-0 testcshared]$ ldd testp
	linux-vdso.so.1 =>  (0x00007fffa87d8000)
	./libgo.so (0x00007f520d4d3000)
	libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f520d2b0000)
	libc.so.6 => /lib64/libc.so.6 (0x00007f520ceee000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f520d7da000)
[hartzelg@spack-0 testcshared]$ ./testp
PASS

If I patch the test.bash script like so:

--- misc/cgo/testcshared/test.bash.orig	2016-11-19 00:00:11.917000000 +0000
+++ misc/cgo/testcshared/test.bash	2016-11-19 00:00:22.081000000 +0000
@@ -107,7 +107,7 @@

 # test0: exported symbols in shared lib are accessible.
 # TODO(iant): using _shared here shouldn't really be necessary.
-$(go env CC) ${GOGCCFLAGS} -I ${installdir} -o testp main0.c libgo.$libext
+$(go env CC) ${GOGCCFLAGS} -I ${installdir} -o testp main0.c ./libgo.$libext
 binpush testp

 output=$(run LD_LIBRARY_PATH=. ./testp)

then I can build 1.7.3 successfully.

Since the 1.7.3 release has been in the wild for a while and I don't see any other issues about this I suspect it's related to the gymanstics that Spack does to support multiple installations of compilers and libraries and etc....

I'm inclined to add a patch to test.bash to Spack's install step (as above) but I'd like to get feedback from more experienced gophers first.

Comments?

[minux]

It seems to be caused by naming conflict with libgo.so provided by gccgo. However, why is libgo.so from gccgo lacks a version in the file name?

[ianlancetaylor]

It's normal to install a file named libgo.so, since the linker will look for an extension of ".so" when resolving a -lgo option. It will be a symlink to the real file with the version number.

I'll add the ./, it's the right thing to do anyhow.

[gopherbot]

CL https://golang.org/cl/33413 mentions this issue.