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cmd/link: building a package that uses cgo errors out with "cannot implicitly include runtime/cgo in a shared library" #47183

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diamondburned opened this issue Jul 14, 2021 · 2 comments

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@diamondburned
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@diamondburned diamondburned commented Jul 14, 2021

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

―❤―▶ go version
go version go1.16.5 linux/amd64

This issue was also reproduced with 1.15.10 and 1.17beta1.

Does this issue reproduce with the latest release?

No: the same code couldn't reproduce the same error on a Debian virtual machine, but a different error was returned. See the other section below.

Yes, but only before running go install -buildmode=shared -linkshared std.

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

go env Output
―❤―▶ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN="/home/diamond/.go/bin"
GOCACHE="/home/diamond/.cache/go-build"
GOENV="/home/diamond/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/diamond/.go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/diamond/.go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/nix/store/9asi3pbr7j0z3n1y80nv2pprgm0chvlv-go-1.16.5/share/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/nix/store/9asi3pbr7j0z3n1y80nv2pprgm0chvlv-go-1.16.5/share/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.16.5"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/tmp/shared-test/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/run/user/1000/go-build672825401=/tmp/go-build -gno-record-gcc-switches"
/etc/os-release
NAME=NixOS
ID=nixos
VERSION="20.09.4302.17a455ce5a2 (Nightingale)"
VERSION_CODENAME=nightingale
VERSION_ID="20.09.4302.17a455ce5a2"
PRETTY_NAME="NixOS 20.09 (Nightingale)"
LOGO="nix-snowflake"
HOME_URL="https://nixos.org/"
DOCUMENTATION_URL="https://nixos.org/learn.html"
SUPPORT_URL="https://nixos.org/community.html"
BUG_REPORT_URL="https://github.com/NixOS/nixpkgs/issues"
lscpu Output
Architecture:                    x86_64
CPU op-mode(s):                  32-bit, 64-bit
Byte Order:                      Little Endian
Address sizes:                   39 bits physical, 48 bits virtual
CPU(s):                          8
On-line CPU(s) list:             0-7
Thread(s) per core:              2
Core(s) per socket:              4
Socket(s):                       1
NUMA node(s):                    1
Vendor ID:                       GenuineIntel
CPU family:                      6
Model:                           142
Model name:                      Intel(R) Core(TM) i5-8250U CPU @ 1.60GHz
Stepping:                        10
CPU MHz:                         2472.405
CPU max MHz:                     3400.0000
CPU min MHz:                     400.0000
BogoMIPS:                        3600.00
Virtualization:                  VT-x
L1d cache:                       128 KiB
L1i cache:                       128 KiB
L2 cache:                        1 MiB
L3 cache:                        6 MiB
NUMA node0 CPU(s):               0-7
Vulnerability Itlb multihit:     KVM: Vulnerable
Vulnerability L1tf:              Mitigation; PTE Inversion; VMX vulnerable
Vulnerability Mds:               Vulnerable; SMT vulnerable
Vulnerability Meltdown:          Vulnerable
Vulnerability Spec store bypass: Vulnerable
Vulnerability Spectre v1:        Vulnerable: __user pointer sanitization and usercopy barriers only; no swapgs barr
                                 iers
Vulnerability Spectre v2:        Vulnerable, IBPB: disabled, STIBP: disabled
Vulnerability Srbds:             Vulnerable
Vulnerability Tsx async abort:   Not affected
Flags:                           fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dt
                                 s acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc ar
                                 t arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni p
                                 clmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4
                                 _1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm
                                  abm 3dnowprefetch cpuid_fault epb invpcid_single ssbd ibrs ibpb stibp tpr_shadow 
                                 vnmi flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms inv
                                 pcid mpx rdseed adx smap clflushopt intel_pt xsaveopt xsavec xgetbv1 xsaves dtherm
                                  ida arat pln pts hwp hwp_notify hwp_act_window hwp_epp md_clear flush_l1d

What did you do?

This issue was opened for two errors: a cannot implicitly include runtime/cgo in a shared library error and a cap out of range error in loader.(*Loader).LoadSyms.

When building this file at c/c.go:

package c

// int add(int i, int j) { return i + j; }
import "C"

func Add(i, j int) int {
	return int(C.add(C.int(i), C.int(j)))
}

using the command go build -buildmode=shared -linkshared ./c, the following error is returned:

# /run/user/1000/go-build3898680118/b018/libshared-test-c.so
/nix/store/9asi3pbr7j0z3n1y80nv2pprgm0chvlv-go-1.16.5/share/go/pkg/tool/linux_amd64/link: cannot implicitly include runtime/cgo in a shared library

The same error is returned when adding import _ "runtime/cgo".

With this code at ./main.go:

package main

import "fmt"

func main() {
	fmt.Println("bruh")
}

built using go build -linkshared ., a similar error is returned:

# shared-test
/nix/store/9asi3pbr7j0z3n1y80nv2pprgm0chvlv-go-1.16.5/share/go/pkg/tool/linux_amd64/link: cannot implicitly include runtime/cgo in a shared library

What did you expect to see?

The first library code built with go build -buildmode=shared -linkshared ./c should succeed, and so should building the main executable with go build -linkshared .. The main executable should be small and dynamically link libstd.so from somewhere else.

What did you see instead?

The two above errors:

# /run/user/1000/go-build3898680118/b018/libshared-test-c.so
/nix/store/9asi3pbr7j0z3n1y80nv2pprgm0chvlv-go-1.16.5/share/go/pkg/tool/linux_amd64/link: cannot implicitly include runtime/cgo in a shared library
# shared-test
/nix/store/9asi3pbr7j0z3n1y80nv2pprgm0chvlv-go-1.16.5/share/go/pkg/tool/linux_amd64/link: cannot implicitly include runtime/cgo in a shared library

This section describes an attempt at reproducing the above bug after running go install -buildmode=shared -linkshared std.

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

diamond@debianVM:/tmp/shared-test$ ~/go-1.16/bin/go version
go version go1.16.6 linux/amd64

Does this issue reproduce with the latest release?

Yes.

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

go env Output
O111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/diamond/.cache/go-build"
GOENV="/home/diamond/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/diamond/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/diamond/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/diamond/go-1.16"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/diamond/go-1.16/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.16.6"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/tmp/shared-test/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build3297561287=/tmp/go-build -gno-record-gcc-switches"
/etc/os-release
PRETTY_NAME="Debian GNU/Linux bullseye/sid"
NAME="Debian GNU/Linux"
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"

What did you do?

See the above section.

What did you expect to see?

See the above section.

What did you see instead?

Building package c yielded a makeslice: cap out of range panic:

diamond@debianVM:/tmp/shared-test$ ~/go-1.16/bin/go build -buildmode=shared -linkshared ./c
# /tmp/go-build2134261352/b018/libshared-test-c.so
panic: runtime error: makeslice: cap out of range

goroutine 1 [running]:
cmd/link/internal/loader.(*Loader).LoadSyms(0xc000786000, 0x87f340)
	/usr/local/go/src/cmd/link/internal/loader/loader.go:2188 +0x125
cmd/link/internal/ld.(*Link).loadlib(0xc00014e000)
	/usr/local/go/src/cmd/link/internal/ld/lib.go:558 +0x3de
cmd/link/internal/ld.Main(0x87f340, 0x20, 0x20, 0x1, 0x7, 0x10, 0x0, 0x0, 0x6e86a7, 0x1b, ...)
	/usr/local/go/src/cmd/link/internal/ld/main.go:244 +0xdbc
main.main()
	/usr/local/go/src/cmd/link/main.go:68 +0x258

The binary actually built successfully with the expected linking:

diamond@debianVM:/tmp/shared-test$ ~/go-1.16/bin/go build -linkshared .
diamond@debianVM:/tmp/shared-test$ ls
c  go.mod  main.go  shared-test
diamond@debianVM:/tmp/shared-test$ ./shared-test
bruh
diamond@debianVM:/tmp/shared-test$ ldd shared-test 
	linux-vdso.so.1 (0x00007fffcfb1e000)
	libstd.so => /home/diamond/go-1.16/pkg/linux_amd64_dynlink/libstd.so (0x00007fd819e56000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fd819c7c000)
	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fd819c76000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fd819c54000)
	/lib64/ld-linux-x86-64.so.2 (0x00007fd81c5eb000)
@mdempsky
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@mdempsky mdempsky commented Jul 14, 2021

@diamondburned
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@diamondburned diamondburned commented Jul 14, 2021

It seems like the second bug is reproducible only after a successful go install -buildmode=shared -linkshared std, so they seem to be two separate issues.

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