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cmd/cgo: building with clang 13 errors out with unknown warning group '-Wunaligned-access' #64943

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bjackman opened this issue Jan 3, 2024 · 8 comments
Closed

cmd/cgo: building with clang 13 errors out with unknown warning group '-Wunaligned-access' #64943

bjackman opened this issue Jan 3, 2024 · 8 comments
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compiler/runtime Issues related to the Go compiler and/or runtime. FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
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@bjackman
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bjackman commented Jan 3, 2024 •
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Go version

go version go1.22-20230908-RC04 cl/563875016 +2fe2f08542 X:fieldtrack,boringcrypto linux/amd64

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

GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/usr/local/google/home/jackmanb/.cache/go-build'
GOENV='/usr/local/google/home/jackmanb/.config/go/env'
GOEXE=''
GOEXPERIMENT='fieldtrack,boringcrypto'
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/usr/local/google/home/jackmanb/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/usr/local/google/home/jackmanb/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/lib/google-golang'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/lib/google-golang/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.22-20230908-RC04 cl/563875016 +2fe2f08542 X:fieldtrack,boringcrypto'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='clang'
CXX='clang++'
CGO_ENABLED='1'
GOMOD='/dev/null'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build2390478846=/tmp/go-build -gno-record-gcc-switches'

What did you do?

mkdir /tmp/go-rand
cd /tmp/go-rand
cat > tst.go << EOF
package main

import (
        "crypto/rand"
)

func main() {
        var r rand.Reader
}
EOF
go build tst.go

What did you expect to see?

Successful build

What did you see instead?

_cgo_export.c:9:32: error: unknown warning group '-Wunaligned-access', ignored [-Werror,-Wunknown-warning-option]

Exit code 1.

In case it's not obvious - I'm a Googler and this is gLinux. I'm reporting via Github per the internal instructions. Apologies if I've misunderstood there!
@bjackman
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bjackman commented Jan 3, 2024 •
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See also #62580 which has the same error message. But the CL of my version is way out of that range that Ian mentioned in the final comment.

@bcmills bcmills added NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. compiler/runtime Issues related to the Go compiler and/or runtime. labels Jan 3, 2024
@bcmills
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bcmills commented Jan 3, 2024 •
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The CL mentioned in #62580 was reapplied in https://go.dev/cl/528935 with an additional -Wunknown-warning-option pragma. Perhaps the version of Clang you're using also doesn't support -Wunknown-warning-option, or doesn't handle that pragma in the same way?

(What does clang --version report for you?)

@bjackman
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bjackman commented Jan 3, 2024 

$ clang --version
clang version 13.0.0 (https://github.com/llvm/llvm-project.git 28ab7ff2d732fb0580486baa02b1383a72cec0cb)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin

Sounds like a good explanation

@bjackman
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bjackman commented Jan 4, 2024

Not sure if this was already obvious but just to confirm, this is not actually specific to package crypto/rand - I get the same thing whenever I import "C" myself too.

@bjackman bjackman changed the title crypto/rand: unknown warning group '-Wunaligned-access', ignored [-Werror,-Wunknown-warning-option] cgo with older Clang: unknown warning group '-Wunaligned-access', ignored [-Werror,-Wunknown-warning-option] Jan 4, 2024
@bjackman
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bjackman commented Jan 4, 2024 •
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Workaround: Get a newer Clang and set the CC environment variable to the clang binary path. Googlers can try go/crosstool-outside-google3#wrapper-scripts.

For anyone else here are some commands I have previously used to successfully build/install Clang from master on a Debian-alike system:

sudo apt install -y cmake && \
git clone https://github.com/llvm/llvm-project.git  && cd llvm-project && \
mkdir build && \
cd build && \
cmake -DLLVM_ENABLE_PROJECTS=clang -DCMAKE_BUILD_TYPE=Release -G "Unix Makefiles" ../llvm && \
make -j $(nproc) && \
sudo make install

@bjackman
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bjackman commented Jan 8, 2024 •
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Was wondering why this isn't affecting more people - suddenly noticed the InstalledDir: /usr/local/bin in #64943 (comment). Apparently at some point I did a system-wide installation of Clang from source (probably when I ran those commands in #64943 (comment)!). So my combination of Clang and Go versions is weird and unusual. So probably this can be deprioritised or maybe it's even WAI.

@bcmills bcmills changed the title cgo with older Clang: unknown warning group '-Wunaligned-access', ignored [-Werror,-Wunknown-warning-option] cmd/cgo: building with clang 13 errors out with unknown warning group '-Wunaligned-access' Jan 9, 2024
@mknyszek mknyszek added this to the Backlog milestone Jan 10, 2024
@mknyszek
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@bjackman Given that this seems to possibly related to your particular version of Clang, I'm going to optimistically close this for now. If you run into any problems with a more stable (?) version of Clang, feel free to comment. Thanks.

@mknyszek mknyszek closed this as not planned Won't fix, can't repro, duplicate, stale Jan 10, 2024
@bjackman
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Just to be clear I don't think this is a case of Clang instability, I think this is probably a genuine incompatibility between Go version 1.22 and Clang version 13.0.0.

However I think it's likely nobody else will ever have that combination of versions so optimistically closing still makes sense.

@mauri870 mauri870 mentioned this issue Jan 26, 2024
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bjackman added a commit to google/page-alloc-bench that referenced this issue Feb 9, 2024
@bjackman
Use rand.Reader isntead of custom generator
13fe853 
The custom generator was a workaround for
golang/go#64943.
@golang golang locked and limited conversation to collaborators Jan 18, 2025
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