cmd/go, cmd/cgo: repeatable builds with Clang 3.8 #15405

EtienneBruines · 2016-04-21T21:26:06Z

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?
go version devel +f8fc371 Thu Apr 21 17:04:01 2016 +0000 linux/amd64
(but GOROOT_BOOTSTRAP is set to an installation of go1.6.2)
What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/etiennebruines/workspaces/go"
GORACE=""
GOROOT="/home/etiennebruines/workspaces/go-master"
GOTOOLDIR="/home/etiennebruines/workspaces/go-master/pkg/tool/linux_amd64"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build179019630=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"

(Tested different versions of `clang` (with different results!), more info down below. )

What did you do?
Attempted to build master branch of Go (currently HEAD is at 40f1d0c )
(more specifically: ./all.bash within the src directory)
What did you expect to see?
No errors.
What did you see instead?
An error within the tests, namely:

--- FAIL: TestCgoConsistentResults (1.10s)
    go_test.go:244: running testgo [build -o /tmp/gotest260338695/cgotest1 cgotest]
    go_test.go:244: running testgo [build -x -o /tmp/gotest260338695/cgotest2 cgotest]
    go_test.go:263: standard error:
    go_test.go:264: WORK=/tmp/go-build737947577
        mkdir -p $WORK/cgotest/_obj/
        mkdir -p $WORK/
        cd /home/etiennebruines/workspaces/go-master/src/cmd/go/testdata/src/cgotest
        CGO_LDFLAGS="-g" "-O2" /home/etiennebruines/workspaces/go-master/pkg/tool/linux_amd64/cgo -objdir $WORK/cgotest/_obj/ -importpath cgotest -- -I $WORK/cgotest/_obj/ m.go
        cd $WORK
        clang-3.8 -fdebug-prefix-map=a=b -c trivial.c
        clang-3.8 -gno-record-gcc-switches -c trivial.c
        cd /home/etiennebruines/workspaces/go-master/src/cmd/go/testdata/src/cgotest
        clang-3.8 -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=$WORK=/tmp/go-build -gno-record-gcc-switches -I $WORK/cgotest/_obj/ -g -O2 -o $WORK/cgotest/_obj/_cgo_main.o -c $WORK/cgotest/_obj/_cgo_main.c
        clang-3.8 -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=$WORK=/tmp/go-build -gno-record-gcc-switches -I $WORK/cgotest/_obj/ -g -O2 -o $WORK/cgotest/_obj/_cgo_export.o -c $WORK/cgotest/_obj/_cgo_export.c
        clang-3.8 -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=$WORK=/tmp/go-build -gno-record-gcc-switches -I $WORK/cgotest/_obj/ -g -O2 -o $WORK/cgotest/_obj/m.cgo2.o -c $WORK/cgotest/_obj/m.cgo2.c
        clang-3.8 -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=$WORK=/tmp/go-build -gno-record-gcc-switches -o $WORK/cgotest/_obj/_cgo_.o $WORK/cgotest/_obj/_cgo_main.o $WORK/cgotest/_obj/_cgo_export.o $WORK/cgotest/_obj/m.cgo2.o -g -O2
        /home/etiennebruines/workspaces/go-master/pkg/tool/linux_amd64/cgo -objdir $WORK/cgotest/_obj/ -dynpackage cgotest -dynimport $WORK/cgotest/_obj/_cgo_.o -dynout $WORK/cgotest/_obj/_cgo_import.go
        cd $WORK
        clang-3.8 -no-pie -c trivial.c
        cd /home/etiennebruines/workspaces/go-master/src/cmd/go/testdata/src/cgotest
        clang-3.8 -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=$WORK=/tmp/go-build -gno-record-gcc-switches -o $WORK/cgotest/_obj/_all.o $WORK/cgotest/_obj/_cgo_export.o $WORK/cgotest/_obj/m.cgo2.o -g -O2 -Wl,-r -nostdlib -Wl,--build-id=none
        /home/etiennebruines/workspaces/go-master/pkg/tool/linux_amd64/compile -o $WORK/cgotest.a -trimpath $WORK -p cgotest -buildid 1491fc40a2d4f2376923084c60120b2fd293fe0e -D _/home/etiennebruines/workspaces/go-master/src/cmd/go/testdata/src/cgotest -I $WORK -pack $WORK/cgotest/_obj/_cgo_gotypes.go $WORK/cgotest/_obj/m.cgo1.go $WORK/cgotest/_obj/_cgo_import.go
        pack r $WORK/cgotest.a $WORK/cgotest/_obj/_all.o # internal
        mkdir -p /tmp/gotest260338695/
        mv $WORK/cgotest.a /tmp/gotest260338695/cgotest2

    go_test.go:2775: building cgotest twice did not produce the same output
FAIL
FAIL    cmd/go  29.068s

Notes

Without clang, this error is not thrown (fails at cmd/cgo: ThreadSanitizer barks about data races in all.bash #14602, so not sure if issue is present)
With clang-3.6, this error is not thrown (not sure why not, but some things are disabled with older clang and newer kernel (4.3))
With clang-3.8, this error is thrown (but cmd/cgo: ThreadSanitizer barks about data races in all.bash #14602 is "fixed").

When running CGO_ENABLED=0, all errors go away (makes sense).

The text was updated successfully, but these errors were encountered:

rsc · 2016-05-27T01:43:18Z

This is unfortunate but not critical for the release.

ianlancetaylor · 2016-06-09T00:30:01Z

Postponing to 1.8.

rsc · 2016-10-21T13:50:04Z

It sounds like we just need to wait for clang and gcc to fix their reproducible build support.

clang

Support for -fdebug-prefix-map was added Oct 2015. Clang 3.7.0 was released Sep 2015, Clang 3.7.1 was released Jan 2016, and Clang 3.8 was released Mar 2016. My guess is the change may have missed the Clang 3.7 point release but was likely in Clang 3.8. Without detecting support for the flag, the test is skipped. This is why we don't see failures before Clang 3.8.

The linux-amd64-clang gomote image is using Clang 3.5, so we don't test this case on the builder.

@bradfitz, is it possible to update to a newer clang? Latest is 3.9.0 released Sep 2 2016. http://llvm.org/releases/

gcc

Support for -fdebug-prefix-map is more widespread, but some versions don't quite work. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69821 shows that while -fdebug-prefix-map did the right thing to the debug symbols, gcc then included that option in the DW_AT_producer field of the dwarf. If the goal of -fdebug-prefix-map=old=new is to eliminate the string "old" from the binary, writing down that option into the binary defeats the purpose. The bug entry says the target milestone is gcc 6 and the discussion there sounds like the decision was not to backport to gcc 5. https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=819176, the Debian entry for this bug, suggests it is fixed in Debian's gcc 5.4.0. It is unclear whether that means the fix is only in Debian's copy or is upstream. It's unclear to me when DW_AT_producer first started recording the whole command line.

Obviously the tests do pass on our gcc builders, and I confirmed that (unlike the clang builder) the gcc on the builder does support the flag, so the test should be running. Perhaps gcc 4.3 had a related problem.

rsc · 2016-10-21T14:32:25Z

See also #13247 and #9206.

ALTree · 2016-10-27T08:41:48Z

Also #5170.

gopherbot · 2016-12-22T00:05:16Z

CL https://golang.org/cl/34675 mentions this issue.

FreeBSD 11 or above uses clang-3.6 or higher by default. Updates #15405. Change-Id: If49ce298130165f9e1525c7fd0fd5aa39099ad53 Reviewed-on: https://go-review.googlesource.com/34675 Reviewed-by: Brad Fitzpatrick <[email protected]> Run-TryBot: Brad Fitzpatrick <[email protected]> TryBot-Result: Gobot Gobot <[email protected]>

rsc · 2017-06-22T23:16:01Z

This is working for me:

$ clang --version
clang version 3.8.0-2ubuntu3~trusty4 (tags/RELEASE_380/final)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
$ CC=clang go test -run=CgoConsistent -v
=== RUN   TestCgoConsistentResults
--- PASS: TestCgoConsistentResults (0.94s)
	go_test.go:310: running testgo [build -o /tmp/gotest742500210/cgotest1 cgotest]
	go_test.go:310: running testgo [build -x -o /tmp/gotest742500210/cgotest2 cgotest]
	go_test.go:323: standard error:
	go_test.go:324: WORK=/tmp/go-build667043988
		mkdir -p $WORK/cgotest/_obj/
		mkdir -p $WORK/
		cd /home/rsc/go/src/cmd/go/testdata/src/cgotest
		CGO_LDFLAGS="-g" "-O2" /home/rsc/go/pkg/tool/linux_amd64/cgo -objdir $WORK/cgotest/_obj/ -importpath cgotest -- -I $WORK/cgotest/_obj/ -g -O2 m.go
		cd $WORK
		clang -fdebug-prefix-map=a=b -c trivial.c
		clang -gno-record-gcc-switches -c trivial.c
		cd $WORK/cgotest/_obj
		clang -I /home/rsc/go/src/cmd/go/testdata/src/cgotest -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=$WORK=/tmp/go-build -gno-record-gcc-switches -I ./ -g -O2 -o ./_cgo_export.o -c _cgo_export.c
		clang -I /home/rsc/go/src/cmd/go/testdata/src/cgotest -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=$WORK=/tmp/go-build -gno-record-gcc-switches -I ./ -g -O2 -o ./m.cgo2.o -c m.cgo2.c
		clang -I /home/rsc/go/src/cmd/go/testdata/src/cgotest -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=$WORK=/tmp/go-build -gno-record-gcc-switches -I ./ -g -O2 -o ./_cgo_main.o -c _cgo_main.c
		cd /home/rsc/go/src/cmd/go/testdata/src/cgotest
		clang -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=$WORK=/tmp/go-build -gno-record-gcc-switches -o $WORK/cgotest/_obj/_cgo_.o $WORK/cgotest/_obj/_cgo_main.o $WORK/cgotest/_obj/_cgo_export.o $WORK/cgotest/_obj/m.cgo2.o -g -O2
		/home/rsc/go/pkg/tool/linux_amd64/cgo -dynpackage cgotest -dynimport $WORK/cgotest/_obj/_cgo_.o -dynout $WORK/cgotest/_obj/_cgo_import.go
		cd $WORK
		clang -no-pie -c trivial.c
		cd /home/rsc/go/src/cmd/go/testdata/src/cgotest
		clang -I . -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=$WORK=/tmp/go-build -gno-record-gcc-switches -o $WORK/cgotest/_obj/_all.o $WORK/cgotest/_obj/_cgo_export.o $WORK/cgotest/_obj/m.cgo2.o -g -O2 -Wl,-r -nostdlib -Wl,--build-id=none
		/home/rsc/go/pkg/tool/linux_amd64/compile -o $WORK/cgotest.a -trimpath $WORK -p cgotest -buildid 7216745655d9549736f59595dc578c7f54579d74 -D _/home/rsc/go/src/cmd/go/testdata/src/cgotest -I $WORK -pack -c=4 $WORK/cgotest/_obj/_cgo_gotypes.go $WORK/cgotest/_obj/m.cgo1.go $WORK/cgotest/_obj/_cgo_import.go
		pack r $WORK/cgotest.a $WORK/cgotest/_obj/_all.o # internal
		mkdir -p /tmp/gotest742500210/
		mv $WORK/cgotest.a /tmp/gotest742500210/cgotest2
		
PASS
ok  	cmd/go	2.705s
$

The builders are on clang 3.9 and it's working there too. Going to assume this is now fixed and that the problem before was that either the specific clang 3.8 being used didn't have -fdebug-prefix-map or did not implement it correctly.

ianlancetaylor changed the title ~~TestCgoConsistentResults~~ cmd/go: TestCgoConsistentResults fails with clang 3.8 Apr 21, 2016

ianlancetaylor added this to the Go1.7 milestone Apr 21, 2016

ianlancetaylor assigned neild Apr 21, 2016

bradfitz mentioned this issue May 17, 2016

website: document the no-me-too policy #14888

Closed

wheelcomplex mentioned this issue May 20, 2016

cmd/cgo: build warning from freebsd/clang: DWARF2 only supports one section per compilation unit #14705

Closed

quentinmit added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label May 26, 2016

rsc modified the milestones: Go1.7Maybe, Go1.7 May 27, 2016

mikioh changed the title ~~cmd/go: TestCgoConsistentResults fails with clang 3.8~~ cmd/go: TestCgoConsistentResults fails with clang 3.8 or gcc 4.3 Jun 3, 2016

ianlancetaylor modified the milestones: Go1.8, Go1.7Maybe Jun 9, 2016

mewmew mentioned this issue Aug 8, 2016

misc/cgo/testsanitizers: Segmentation fault using GCC 6.1.1 (and Clang 3.8.1) #16636

Closed

rsc unassigned neild Oct 21, 2016

rsc modified the milestones: Go1.9, Go1.8 Oct 21, 2016

rsc changed the title ~~cmd/go: TestCgoConsistentResults fails with clang 3.8 or gcc 4.3~~ cmd/go, cmd/cgo: repeatable builds with Clang 3.8 Oct 21, 2016

ianlancetaylor mentioned this issue Dec 16, 2016

cmd/go: TestCgoConsistentResults fails with clang-3.8 #18338

Closed

rsc closed this as completed Jun 22, 2017

golang locked and limited conversation to collaborators Jun 22, 2018

gopherbot added the FrozenDueToAge label Jun 22, 2018

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cmd/go, cmd/cgo: repeatable builds with Clang 3.8 #15405

cmd/go, cmd/cgo: repeatable builds with Clang 3.8 #15405

EtienneBruines commented Apr 21, 2016 •

edited

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rsc commented May 27, 2016

ianlancetaylor commented Jun 9, 2016

rsc commented Oct 21, 2016

rsc commented Oct 21, 2016

ALTree commented Oct 27, 2016

gopherbot commented Dec 22, 2016

rsc commented Jun 22, 2017

cmd/go, cmd/cgo: repeatable builds with Clang 3.8 #15405

cmd/go, cmd/cgo: repeatable builds with Clang 3.8 #15405

Comments

EtienneBruines commented Apr 21, 2016 • edited Loading

Notes

rsc commented May 27, 2016

ianlancetaylor commented Jun 9, 2016

rsc commented Oct 21, 2016

rsc commented Oct 21, 2016

ALTree commented Oct 27, 2016

gopherbot commented Dec 22, 2016

rsc commented Jun 22, 2017

EtienneBruines commented Apr 21, 2016 •

edited

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