cmd/go: go list -e -compiled -json does not populate Error when cgo preprocessing fails

[dominikh]

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

$ go version
go version go1.14.1 linux/amd64
go version devel +57e32c4fbd Sun May 10 14:43:46 2020 +0000 linux/amd64

What's wrong

When cgo preprocessing fails, go list -json -compiled -e prints an error on stderr and exits with a non-zero status, but it does not populate the Error field of the package. It is possible to detect that something went wrong because CompiledGoFiles isn't populated, but we can't tell why it failed. Two common reasons are a missing C compiler, and missing libraries.

Example output

$ CC=/does/not/exist go list -json -compiled -e runtime/cgo
# runtime/cgo
fork/exec /does/not/exist: no such file or directory
{
	"Dir": "/nix/store/sylhlk3fd3xik0d8hqrm20zxnfc3x7m4-go-1.14.1/share/go/src/runtime/cgo",
	"ImportPath": "runtime/cgo",
	"Name": "cgo",
	"Doc": "Package cgo contains runtime support for code generated by the cgo tool.",
	"Target": "/nix/store/sylhlk3fd3xik0d8hqrm20zxnfc3x7m4-go-1.14.1/share/go/pkg/linux_amd64/runtime/cgo.a",
	"Root": "/nix/store/sylhlk3fd3xik0d8hqrm20zxnfc3x7m4-go-1.14.1/share/go",
	"Match": [
		"runtime/cgo"
	],
	"Goroot": true,
	"Standard": true,
	"Stale": true,
	"StaleReason": "build ID mismatch",
	"GoFiles": [
		"callbacks.go",
		"callbacks_traceback.go",
		"iscgo.go",
		"mmap.go",
		"setenv.go",
		"sigaction.go"
	],
	"CgoFiles": [
		"cgo.go"
	],
	"IgnoredGoFiles": [
		"callbacks_aix.go",
		"dragonfly.go",
		"freebsd.go",
		"netbsd.go",
		"openbsd.go",
		"signal_darwin_armx.go"
	],
	"CFiles": [
		"gcc_context.c",
		"gcc_fatalf.c",
		"gcc_libinit.c",
		"gcc_linux_amd64.c",
		"gcc_mmap.c",
		"gcc_setenv.c",
		"gcc_sigaction.c",
		"gcc_traceback.c",
		"gcc_util.c"
	],
	"HFiles": [
		"libcgo.h",
		"libcgo_unix.h"
	],
	"SFiles": [
		"asm_amd64.s",
		"gcc_amd64.S"
	],
	"CgoCFLAGS": [
		"-Wall",
		"-Werror"
	],
	"CgoLDFLAGS": [
		"-lpthread"
	],
	"Imports": [
		"C",
		"unsafe"
	],
	"Deps": [
		"unsafe"
	]
}

Related: #34229 and #25842

/cc @bcmills @matloob @heschik

[jayconrod]

This has the same root cause as the two linked issues: #34229 and #25842

Currently, go list -e populates the Error field with errors it encounters when loading the package dependency graph. It should also populate the Error field with errors encountered when running cgo, the compiler, and other commands.

[SeanTolstoyevski]

This issue also occurs when coding a CGO module with VSCode.

now is there anything that can be making?

[thalesfsp]

This issue also occurs when coding a CGO module with VSCode.

now is there anything that can be making?

Do u know how to disable this message on VSCode?

[zyfdegh]

There's no quick solution currently, but to figure out what's wrong VSCode running the go list command, execute this manually @SeanTolstoyevski @thalesfsp

go list -e -json -compiled -x  /absolute/path/to/yourpkg/src.go

For me, it outputs

WORK=/tmp/go-build2892322839
mkdir -p $WORK/b001/
cd /absolute/path/to/yourpkg
TERM='dumb' CGO_LDFLAGS='"-g" "-O2" "-L/absolute/path/to/yourpkg/lib" "-lYourFunc"' /usr/lib/go/pkg/tool/linux_amd64/cgo -objdir $WORK/b001/ -importpath command-line-arguments -- -I $WORK/b001/ -g -O2 -I/absolute/path/to/yourpkg/include -std=c99 ./src.go
# command-line-arguments
In file included from yourpkg/src.go:10:
yourpkg/include/SomeWapper.h:1:10: fatal error: iostream: No such file or directory
    1 | #include <iostream>
      |          ^~~~~~~~~~
compilation terminated.
{
        "Dir": "/absolute/path/to/yourpkg",
        "ImportPath": "command-line-arguments",
        "Name": "yourpkg",
        "Match": [
                "/absolute/path/to/yourpkg/src.go"
        ],
        "Stale": true,
        "StaleReason": "build ID mismatch",
        "CgoFiles": [
                "src.go"
        ],

# ... more JSON, but no 'CompiledGoFiles' field, VSCode cannot interpret

So I know it's due to the C++ headers included, which is not allowed. Refer golang-nuts

To dismiss the warnings, ignore files (refer) in vscode settings.json (not recommended, file tree won't show)

    "files.exclude": {
        "**/vscode/relative/yourpkg": true,
    },

On the PROBLEMS tab, click filter icon to the right, Hide Excluded Files.

[FH0]

There are two errors in my cgo program, but I can run it fine. I've searched a lot but still don't know how to fix these two errors that shouldn't be there. I'll just have to try my luck here.

root@ubuntu2004 /root/go/src/learn
# go list -e -json -compiled -x main.go
WORK=/tmp/go-build172218443
mkdir -p $WORK/b001/
cd /root/go/src/learn
TERM='dumb' CGO_LDFLAGS='"-g" "-O2"' /usr/local/go/pkg/tool/linux_amd64/cgo -objdir $WORK/b001/ -importpath command-line-arguments -- -I $WORK/b001/ -g -O2 ./main.go
cd $WORK
gcc -fno-caret-diagnostics -c -x c - -o /dev/null || true
gcc -Qunused-arguments -c -x c - -o /dev/null || true
gcc -fdebug-prefix-map=a=b -c -x c - -o /dev/null || true
gcc -gno-record-gcc-switches -c -x c - -o /dev/null || true
cd $WORK/b001
TERM='dumb' gcc -I /root/go/src/learn -fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=$WORK/b001=/tmp/go-build -gno-record-gcc-switches -I ./ -g -O2 -o ./_x001.o -c _cgo_export.c
TERM='dumb' gcc -I /root/go/src/learn -fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=$WORK/b001=/tmp/go-build -gno-record-gcc-switches -I ./ -g -O2 -o ./_x002.o -c main.cgo2.c
TERM='dumb' gcc -I /root/go/src/learn -fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=$WORK/b001=/tmp/go-build -gno-record-gcc-switches -I ./ -g -O2 -o ./_cgo_main.o -c _cgo_main.c
cd /root/go/src/learn
TERM='dumb' gcc -I . -fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=$WORK/b001=/tmp/go-build -gno-record-gcc-switches -o $WORK/b001/_cgo_.o $WORK/b001/_cgo_main.o $WORK/b001/_x001.o $WORK/b001/_x002.o -g -O2
TERM='dumb' /usr/local/go/pkg/tool/linux_amd64/cgo -dynpackage main -dynimport $WORK/b001/_cgo_.o -dynout $WORK/b001/_cgo_import.go
{
        "Dir": "/root/go/src/learn",
        "ImportPath": "command-line-arguments",
        "Name": "main",
        "Target": "/root/go/bin/main",
        "Root": "/root/go",
        "Match": [
                "main.go"
        ],
        "Stale": true,
        "StaleReason": "stale dependency: fmt",
        "CgoFiles": [
                "main.go"
        ],
        "CompiledGoFiles": [
                "/root/.cache/go-build/23/23c8fe3c2183dd4d83d20fc531e6cd5bf2b241f58b7d34e14637c5613006c72d-d",
                "/root/.cache/go-build/13/135d992523728ea58aba4fa664090b30fed3f393c098cec69dafe491fa19151f-d",
                "/root/.cache/go-build/20/208f6d19c1a23764cd62b4ec0928985a90bf7a1604e95051639db0f0f7d1e439-d"
        ],
        "Imports": [
                "C",
                "fmt",
                "unsafe",
                "runtime/cgo",
                "syscall"
        ],
        "Deps": [
                "errors",
                "fmt",
                "internal/abi",
                "internal/bytealg",
                "internal/cpu",
                "internal/fmtsort",
                "internal/goarch",
                "internal/goexperiment",
                "internal/goos",
                "internal/itoa",
                "internal/oserror",
                "internal/poll",
                "internal/race",
                "internal/reflectlite",
                "internal/syscall/execenv",
                "internal/syscall/unix",
                "internal/testlog",
                "internal/unsafeheader",
                "io",
                "io/fs",
                "math",
                "math/bits",
                "os",
                "path",
                "reflect",
                "runtime",
                "runtime/cgo",
                "runtime/internal/atomic",
                "runtime/internal/math",
                "runtime/internal/sys",
                "runtime/internal/syscall",
                "sort",
                "strconv",
                "sync",
                "sync/atomic",
                "syscall",
                "time",
                "unicode",
                "unicode/utf8",
                "unsafe"
        ]
}

[FH0]

After I commented line 81, the problem was solved.

[toriato]

There may be a problem caused by the architecture of the C toolchain you are using being different from the GOARCH environment variable.
If you are using vscode, you can try setting the GOARCH value through the build.env.

{
  "gopls": {
    "build.env": {
      "GOARCH": "386"
    }
  }
}

[Xosrov]

I was getting this issue using the msys mingw version of Go with CGo. Adding these lines to settings.json fixed it:

"go.goroot": "C:\\msys64\\mingw64\\lib\\go",
    "go.testEnvVars": {
        "CGO_ENABLED": 1,
        "PATH": "C:\\msys64\\mingw64\\bin"
    },
    "go.toolsEnvVars": {
        "CGO_ENABLED": 1,
        "PATH": "C:\\msys64\\mingw64\\bin"
    },

It also fixes the gcc not found problems when testing cgo code from vscode.

[Santamian]

After I commented line 81, the problem was solved.

could you show what file you are editing ? i can't tell exactly what you're doing i know it is json but how do i get to it ?

[FH0]

@StitchyKid