cmd/go: linker issue when using clang with cgo on linux #11002
Comments
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What is the output of "pkg-config opencv"? I assume you are getting this error when you run "go build". Can you add the output of "go build -x"? Go is probably passing the -r option (as -Wl,-r), but I doubt it is passing the -shared option. Go 1.4 never passes a -shared option. We need to find out where -shared is coming from, and why. I have no idea why GCC and clang would be behaving differently here. The error message is from the linker, and normally on GNU/Linux both GCC and clang use the same linker. |
ianlancetaylor
changed the title
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The output of I don't think this relates directly as it is about the Also interesting a pastebin from someone else who had the same problem. |
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There is nothing in the way that the Go tool is invoking clang++ that should cause it to pass -shared to the linker. Run go build -work. That will print out a value for WORK and leave files in that directory. Set the environment variable WORK to the value it prints out and run the failing command: /usr/bin/clang++ -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -o $WORK/github.com/bodokaiser/retina/image/_obj/_all.o $WORK/github.com/bodokaiser/retina/image/_obj/_cgo_export.o $WORK/github.com/bodokaiser/retina/image/_obj/image.cgo2.o $WORK/github.com/bodokaiser/retina/image/_obj/image.cc.o -g -O2 -L/usr/local/lib -Wl,-r -nostdlib /usr/bin/../lib/gcc/x86_64-alpine-linux-musl/4.9.2/libgcc.a -Wl,--build-id=none and add a -v option as well. It should fail the same way, but should show how clang++ invoked the linker. Show us the complete compiler output. |
go build -x -v -work ./...
WORK=/tmp/go-build288906313
github.com/bodokaiser/retina/image
mkdir -p $WORK/github.com/bodokaiser/retina/image/_obj/
mkdir -p $WORK/github.com/bodokaiser/retina/
cd /srv/src/github.com/bodokaiser/retina/image
pkg-config --cflags opencv
pkg-config --libs opencv
CGO_LDFLAGS="-g" "-O2" "-L/usr/local/lib" "-lopencv_shape" "-lopencv_stitching" "-lopencv_objdetect" "-lopencv_superres" "-lopencv_videostab" "-lopencv_calib3d" "-lopencv_features2d" "-lopencv_highgui" "-lopencv_videoio" "-lopencv_imgcodecs" "-lopencv_video" "-lopencv_photo" "-lopencv_ml" "-lopencv_imgproc" "-lopencv_flann" "-lopencv_core" "-lopencv_hal" /usr/lib/go/pkg/tool/linux_amd64/cgo -objdir $WORK/github.com/bodokaiser/retina/image/_obj/ -- -I/usr/local/include/opencv -I/usr/local/include -I $WORK/github.com/bodokaiser/retina/image/_obj/ image.go
/usr/lib/go/pkg/tool/linux_amd64/6c -F -V -w -trimpath $WORK -I $WORK/github.com/bodokaiser/retina/image/_obj/ -I /usr/lib/go/pkg/linux_amd64 -o $WORK/github.com/bodokaiser/retina/image/_obj/_cgo_defun.6 -D GOOS_linux -D GOARCH_amd64 $WORK/github.com/bodokaiser/retina/image/_obj/_cgo_defun.c
/usr/bin/clang -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -print-libgcc-file-name
/usr/bin/clang -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -I/usr/local/include/opencv -I/usr/local/include -I $WORK/github.com/bodokaiser/retina/image/_obj/ -g -O2 -o $WORK/github.com/bodokaiser/retina/image/_obj/_cgo_main.o -c $WORK/github.com/bodokaiser/retina/image/_obj/_cgo_main.c
/usr/bin/clang -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -I/usr/local/include/opencv -I/usr/local/include -I $WORK/github.com/bodokaiser/retina/image/_obj/ -g -O2 -o $WORK/github.com/bodokaiser/retina/image/_obj/_cgo_export.o -c $WORK/github.com/bodokaiser/retina/image/_obj/_cgo_export.c
/usr/bin/clang -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -I/usr/local/include/opencv -I/usr/local/include -I $WORK/github.com/bodokaiser/retina/image/_obj/ -g -O2 -o $WORK/github.com/bodokaiser/retina/image/_obj/image.cgo2.o -c $WORK/github.com/bodokaiser/retina/image/_obj/image.cgo2.c
/usr/bin/clang++ -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -I/usr/local/include/opencv -I/usr/local/include -I $WORK/github.com/bodokaiser/retina/image/_obj/ -g -O2 -std=c++11 -o $WORK/github.com/bodokaiser/retina/image/_obj/image.cc.o -c ./image.cc
/usr/bin/clang++ -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -o $WORK/github.com/bodokaiser/retina/image/_obj/_cgo_.o $WORK/github.com/bodokaiser/retina/image/_obj/_cgo_main.o $WORK/github.com/bodokaiser/retina/image/_obj/_cgo_export.o $WORK/github.com/bodokaiser/retina/image/_obj/image.cgo2.o $WORK/github.com/bodokaiser/retina/image/_obj/image.cc.o -g -O2 -L/usr/local/lib -lopencv_shape -lopencv_stitching -lopencv_objdetect -lopencv_superres -lopencv_videostab -lopencv_calib3d -lopencv_features2d -lopencv_highgui -lopencv_videoio -lopencv_imgcodecs -lopencv_video -lopencv_photo -lopencv_ml -lopencv_imgproc -lopencv_flann -lopencv_core -lopencv_hal
/usr/lib/go/pkg/tool/linux_amd64/cgo -objdir $WORK/github.com/bodokaiser/retina/image/_obj/ -dynimport $WORK/github.com/bodokaiser/retina/image/_obj/_cgo_.o -dynout $WORK/github.com/bodokaiser/retina/image/_obj/_cgo_import.c
/usr/lib/go/pkg/tool/linux_amd64/6c -F -V -w -trimpath $WORK -I $WORK/github.com/bodokaiser/retina/image/_obj/ -I /usr/lib/go/pkg/linux_amd64 -o $WORK/github.com/bodokaiser/retina/image/_obj/_cgo_import.6 -D GOOS_linux -D GOARCH_amd64 $WORK/github.com/bodokaiser/retina/image/_obj/_cgo_import.c
/usr/bin/clang++ -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -o $WORK/github.com/bodokaiser/retina/image/_obj/_all.o $WORK/github.com/bodokaiser/retina/image/_obj/_cgo_export.o $WORK/github.com/bodokaiser/retina/image/_obj/image.cgo2.o $WORK/github.com/bodokaiser/retina/image/_obj/image.cc.o -g -O2 -L/usr/local/lib -Wl,-r -nostdlib /usr/bin/../lib/gcc/x86_64-alpine-linux-musl/4.9.2/libgcc.a -Wl,--build-id=none
# github.com/bodokaiser/retina/image
/usr/bin/ld: -r and -shared may not be used together
clang-3.6: error: linker command failed with exit code 1 (use -v to see invocation)Still no |
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Thanks for that output, but what I need to see is the output of the final /usr/bin/clang++ line when you add the -v option to that line. That is, please do exactly what I asked for above. I don't need -v added to go build. I need it added to clang++. Thanks. |
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Ah, right. Sorry. The Go linker will create a temporary file, but it won't save it. Bother. OK, try creating a foo.o file from C, and run /usr/bin/clang++ -v -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -o foo foo.o -g -O2 -L/usr/local/lib -Wl,-r -nostdlib /usr/bin/../lib/gcc/x86_64-alpine-linux-musl/4.9.2/libgcc.a -Wl,--build-id=none |
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Another way to do the same is:
go build -x -ldflags "-extldflags -v" ./...
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foo.c (if it matters) #include <stdlib.h>
int main() {
return 0;
}/usr/bin/clang++ -v -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -o foo foo.o
-g -O2 -L/usr/local/lib -Wl,-r -nostdlib /usr/bin/../lib/gcc/x86_64-alpine-linux-musl/4.9.2/libgcc.a -Wl,--build-id=none
clang version 3.6.1 (tags/RELEASE_361/final)
Target: x86_64-alpine-linux-musl
Thread model: posix
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-alpine-linux-musl/4.9.2
Found candidate GCC installation: /usr/lib/gcc/x86_64-alpine-linux-musl/4.9.2
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-alpine-linux-musl/4.9.2
Candidate multilib: .;@m64
Selected multilib: .;@m64
"/usr/bin/ld" -pie -z relro --hash-style=gnu --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib/ld-musl-x86_64.so.1 -o foo -L/usr/local/lib -L/usr/bin/../lib/gcc/x86_64-alpine-linux-musl/4.9.2 -L/usr/bin/../lib/gcc/x86_64-alpine-linux-musl/4.9.2/../../../../x86_64-alpine-linux-musl/lib -L/usr/bin/../lib/gcc/x86_64-alpine-linux-musl/4.9.2/../../.. -L/usr/bin/../lib -L/lib -L/usr/lib foo.o -r /usr/bin/../lib/gcc/x86_64-alpine-linux-musl/4.9.2/libgcc.a --build-id=none
/usr/bin/ld: -r and -shared may not be used together
clang-3.6: error: linker command failed with exit code 1 (use -v to see invocation) |
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Thanks. It's a very misleading message from the GNU linker. The actual problem is the -pie option. The GNU linker rejects using -pie -r. Unfortunately the GNU linker has no way to turn off a -pie option. So we need to arrange for clang++ to not pass -pie to the linker. That means we need to find out why it is doing it and how to disable it. The version of clang++ installed on my system (3.4) does not pass a -pie option. I can't find any evidence that LLVM likes to pass -pie on systems other than Android. Does your system have a file /usr/lib/gcc/x86_64-alpine-linux-musl/4.9.2/specs ? If so, please add it here. Otherwise I think we need to pass this to the LLVM developers. Why it LLVM passing -pie? How can we get it to stop? |
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vanila.spec %include <hardenednossp.specs>
%include <hardenednopie.specs>
*esp_link_now:
*esp_link_relro:
*esp_cc1_strict_overflow:hardenednopie.spec *esp_cc1_pie:
*esp_options_pie:
*esp_link_pie_check:
*esp_link_pie:hardenednopiessp.specs %include <hardenednossp.specs>
%include <hardenednopie.specs>hardenednossp.specs *esp_cc1_ssp:
*esp_options_ssp:Seems you are right that one of the specs are setting the Am I right that the distributor of the gcc package adds the |
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I can't see the actual contents of the spec files--I think that github markdown syntax is hiding them. Is there some way to disable markdown? Yes, in this case, it is the distributor of GCC who is added the spec files. GCC does not distribute spec files like this. |
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This is strange? Are you answering per email? However thank you for your support! I will show this the distributor maybe this will save a good portion of time for further docker deploys :D |
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I'm not answering by e-mail, I'm looking at http://golang.org/issue/11002 and failing to see the contents of the spec files. I just see lines like "*esp_cc1_ssp:" but nothing else. Is that what the spec files look like? |
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Yes, they are just some lines of code. In the worst case you could still look it up on github |
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I would find it helpful to see those lines. Where would I look on github to find them? Thanks. |
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You do not use GitHub very often? |
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I am not at all an expert user of github. When I go to that link, which is exactly what I have been doing, I see just '*' lines and %include lines. I do not see anything else. I would expect to see more text, along the lines of %{!-r:-pie} or something. |
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If you do not see more you are expecting too much. Each of the files only had about one to five lines. One contains some option where "pie" is a part of so I guess this is the "bad one".
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Ah, in that case, these files are not the problem. I still don't know where the -pie option is coming from. I agree that it must be some distro-specific patch, though. |
Hello,
1. What go version do I use?
go version go1.4.2 linux/amd64.2. What operating system do I use?
alpine linux as official docker image build steps can be taken from this Dockerfile.
3. What did I do?
I want to compile a go project which uses cgo to do some work in opencv.
You can see the file which imports C.
4. What did I expect to happen?
That cgo works platform independent across unix* and between gcc and clang.
5. What happened instead?
6. What did I do as workaround?
I prefixed the go command with
CC="" CXX=""so that go uses gcc instead of clang.Possible related issues:
Best Bodo
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