wrong ELF class error: How to compile 64 bit binary on Solaris 11 using gccgo

[Amandeep Gautam]

Hi,

   I am trying to compile a 64bit executable using gccgo on Solaris 11/10. Following is what I have tried:

CGO_LDFLAGS='-m64' go build hello_world.go

GOARCH=sparc64 CGO_LDFLAGS='-m64' go build hello_world.go

Below is the output of the first command:

amandeep@s113ldom1:~/workspace$ CGO_LDFLAGS='-m64' go build pqrs.go 

# command-line-arguments

ld: warning: file $WORK/b001/_pkg_.a(_go_.o): wrong ELF class: ELFCLASS32

Undefined                       first referenced

 symbol                             in file

main.main                           /usr/gnu/lib/gcc/sparc-sun-solaris2.11/8.2.1/../../../sparcv9/libgo.so

__go_init_main                      /usr/gnu/lib/gcc/sparc-sun-solaris2.11/8.2.1/../../../sparcv9/libgo.so

ld: fatal: symbol referencing errors

collect2: error: ld returned 1 exit status

However, I am able to generate 64 bit executable for c++ helloworld using just gcc, so I am hoping it boils down to passing the right set of flags. For example:

amandeep@s113ldom1:~/workspace$ /usr/gnu/bin/gcc -m64 helloworld.c 

amandeep@s113ldom1:~/workspace$ file ./a.out 

./a.out:        ELF 64-bit MSB executable SPARCV9 Version 1, dynamically linked, not stripped, no debugging information available

amandeep@s113ldom1:~/workspace$ file /usr/gnu/bin/gcc

/usr/gnu/bin/gcc:       ELF 32-bit MSB executable SPARC32PLUS Version 1, V8+ Required, dynamically linked, not stripped

How would you compile a 64 bit executable for Solaris using gccgo?

[Ian Lance Taylor]

CGO_LDFLAGS only affects your program if it actually uses cgo.

Does it work to do
go build -gccgoflags=-m64
?

Ian

[aman...@cohesity.com]

Yes, this works for a simple program I have. Now I modified the helloworld to use glog as follows:

package main                                                                   

                                                                               

import (                                                                       

  "fmt"                                                                        

  "github.com/golang/glog"                                                     

)                                                                              

                                                                               

func main() {                                                                  

  fmt.Println("Hello world....")                                               

  glog.Info("Hello world...")                                                  

}                                                                              

But now I get another error from libglog.a:

amandeep@s113ldom1:~/workspace$ go build -gccgoflags=-m64 helloworld.go 

# command-line-arguments

ld: warning: file /opt/go_pkgs/pkg/gccgo_solaris_sparc/github.com/golang/libglog.a(_go_.o): wrong ELF class: ELFCLASS32

Undefined                       first referenced

 symbol                             in file

github_com_golang_glog..import      $WORK/b001/_pkg_.a(_go_.o)

github_com_golang_glog.Info         $WORK/b001/_pkg_.a(_go_.o)

ld: fatal: symbol referencing errors

collect2: error: ld returned 1 exit status

So, I thought recompiling glog with 64 bit option would help. None of the following helped:

sudo GOPATH=/opt/go_pkgs/ CGO_LDFLAGS='-m64' go install

sudo GOPATH=/opt/go_pkgs/ go install -gccgoflags '-m64'

sudo GOPATH=/opt/go_pkgs/ go install -gccgoflags='-m64'

All of these generate the following:

amandeep@s113ldom1:/opt/go_pkgs/src/github.com/golang/glog$ file /opt/go_pkgs/pkg/gccgo_solaris_sparc/github.com/golang/libglog.a 

/opt/go_pkgs/pkg/gccgo_solaris_sparc/github.com/golang/libglog.a:       current ar archive, 32-bit symbol table

Regards,

Aman

[Ian Lance Taylor]

For a package that uses cgo, you'll need to use -gccgoflags=-m64 and
also set both CGO_CFLAGS and CGO_LDFLAGS to -m64.

Ian

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[aman...@cohesity.com]

Seems like even that does not seem to work. Please see:

amandeep@s113ldom1:/opt/go_pkgs/src/github.com/golang/glog$ sudo GOPATH=/opt/go_pkgs  CGO_CFLAGS='-m64' CGO_LDFLAGS='-m64' go install -x -gccgoflags=-m64

WORK=/tmp/go-build357879094

mkdir -p $WORK/b001/

cd $WORK

/usr/gnu/bin/gccgo -fgo-importcfg=/dev/null -c -x c - || true

cd /opt/go_pkgs/src/github.com/golang/glog

/usr/gnu/bin/gccgo -c -g -fdebug-prefix-map=$WORK=/tmp/go-build -gno-record-gcc-switches -fgo-pkgpath=github.com/golang/glog -o $WORK/b001/_go_.o -I $WORK/b001/_importcfgroot_ -m64 ./glog.go ./glog_file.go

echo '  .section .go.buildid,"e"' >> $WORK/b001/_buildid.s

echo '  .byte 0x64,0x71,0x65,0x31,0x73,0x55,0x39,0x39' >> $WORK/b001/_buildid.s

echo '  .byte 0x62,0x56,0x7a,0x36,0x52,0x57,0x35,0x74' >> $WORK/b001/_buildid.s

echo '  .byte 0x64,0x55,0x59,0x4f,0x2f,0x64,0x71,0x65' >> $WORK/b001/_buildid.s

echo '  .byte 0x31,0x73,0x55,0x39,0x39,0x62,0x56,0x7a' >> $WORK/b001/_buildid.s

echo '  .byte 0x36,0x52,0x57,0x35,0x74,0x64,0x55,0x59' >> $WORK/b001/_buildid.s

echo '  .byte 0x4f' >> $WORK/b001/_buildid.s

echo '' >> $WORK/b001/_buildid.s

/usr/gnu/bin/gccgo -xassembler-with-cpp -I $WORK/b001/ -c -o $WORK/b001/_buildid.o -D GOOS_solaris -D GOARCH_sparc -D GOPKGPATH=github_com_golang_glog $WORK/b001/_buildid.s

ar rcD $WORK/b001/_pkg_.a $WORK/b001/_go_.o $WORK/b001/_buildid.o

/usr/gnu/libexec/gcc/sparc-sun-solaris2.11/8.2.1/buildid -w $WORK/b001/_pkg_.a # internal

cp $WORK/b001/_pkg_.a /root/.cache/go-build/9d/9de1b3b9dc941395e2c0ba0bd363f9af9f8dc5c62c84b2d248c274ba14a2bcd7-d # internal

mkdir -p /opt/go_pkgs/pkg/gccgo_solaris_sparc/github.com/golang/

cp $WORK/b001/_pkg_.a /opt/go_pkgs/pkg/gccgo_solaris_sparc/github.com/golang/libglog.a

rm -r $WORK/b001/

amandeep@s113ldom1:/opt/go_pkgs/src/github.com/golang/glog$ file /opt/go_pkgs/pkg/gccgo_solaris_sparc/github.com/golang/libglog.a

/opt/go_pkgs/pkg/gccgo_solaris_sparc/github.com/golang/libglog.a:       current ar archive, 32-bit symbol table

In the above output, I can see that -m64 flag is being passed to gcc, but somehow does not seem to apply everywhere (one of the gccgo invocation does not have -m64 flag). I tried to look at the generated archive and one of the members is still 32bit  MSB executable. Please look:

amandeep@s113ldom1:~/workspace$ ar -t /opt/go_pkgs/pkg/gccgo_solaris_sparc/github.com/golang/libglog.a

_go_.o

_buildid.o

amandeep@s113ldom1:~/workspace$ ar -xv /opt/go_pkgs/pkg/gccgo_solaris_sparc/github.com/golang/libglog.a ./_go_.o ./_buildid.o

x - _go_.o

x - _buildid.o

amandeep@s113ldom1:~/workspace$ file ./_buildid.o 

./_buildid.o:   ELF 32-bit MSB relocatable SPARC Version 1

amandeep@s113ldom1:~/workspace$ file ./_go_.o 

./_go_.o:       ELF 64-bit MSB relocatable SPARCV9 Version 1

Could that be the reason?

I also tried providing GOARCH=sprac64 flag to see if that helps, but it didn't. Similar output, just the file is generated in a different folder. Please see:

amandeep@s113ldom1:/opt/go_pkgs/src/github.com/golang/glog$ sudo GOPATH=/opt/go_pkgs  CGO_CFLAGS='-m64' CGO_LDFLAGS='-m64' GOARCH=sparc64 CGO_ENABLED=1 go install -x -gccgoflags=-m64

WORK=/tmp/go-build328208181

mkdir -p $WORK/b001/

cd $WORK

/usr/gnu/bin/gccgo -fgo-importcfg=/dev/null -c -x c - || true

cd /opt/go_pkgs/src/github.com/golang/glog

/usr/gnu/bin/gccgo -c -g -fdebug-prefix-map=$WORK=/tmp/go-build -gno-record-gcc-switches -fgo-pkgpath=github.com/golang/glog -o $WORK/b001/_go_.o -I $WORK/b001/_importcfgroot_ -m64 ./glog.go ./glog_file.go

echo '  .section .go.buildid,"e"' >> $WORK/b001/_buildid.s

echo '  .byte 0x79,0x71,0x58,0x37,0x74,0x64,0x76,0x6c' >> $WORK/b001/_buildid.s

echo '  .byte 0x7a,0x59,0x53,0x39,0x41,0x6a,0x30,0x58' >> $WORK/b001/_buildid.s

echo '  .byte 0x34,0x53,0x78,0x39,0x2f,0x79,0x71,0x58' >> $WORK/b001/_buildid.s

echo '  .byte 0x37,0x74,0x64,0x76,0x6c,0x7a,0x59,0x53' >> $WORK/b001/_buildid.s

echo '  .byte 0x39,0x41,0x6a,0x30,0x58,0x34,0x53,0x78' >> $WORK/b001/_buildid.s

echo '  .byte 0x39' >> $WORK/b001/_buildid.s

echo '' >> $WORK/b001/_buildid.s

/usr/gnu/bin/gccgo -xassembler-with-cpp -I $WORK/b001/ -c -o $WORK/b001/_buildid.o -D GOOS_solaris -D GOARCH_sparc64 -D GOPKGPATH=github_com_golang_glog $WORK/b001/_buildid.s

ar rcD $WORK/b001/_pkg_.a $WORK/b001/_go_.o $WORK/b001/_buildid.o

/usr/gnu/libexec/gcc/sparc-sun-solaris2.11/8.2.1/buildid -w $WORK/b001/_pkg_.a # internal

cp $WORK/b001/_pkg_.a /root/.cache/go-build/a4/a47820a6bcb6e72c26a3be36129e80b12a0f0193dd5959e2c7304a3b169d9af8-d # internal

mkdir -p /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/

cp $WORK/b001/_pkg_.a /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a

rm -r $WORK/b001/

amandeep@s113ldom1:/opt/go_pkgs/src/github.com/golang/glog$ file /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a

/opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a:     current ar archive, 32-bit symbol table

I also gave compiling the helloworld file a try with this newly generated lib (with different flags) but the compilation still faces the previous problem. Did I miss something? Please let me know.

Regards,

Aman

[Ian Lance Taylor]

OK, new suggestion. Also set the environment variable CC="gcc -m64".

Ian

[aman...@cohesity.com]

nopes...doesn't work either. I tried both variations...with and without GOARCH=sparc64 flag. Following is the output with sparc64 flag:

amandeep@s113ldom1:/opt/go_pkgs/src/github.com/golang/glog$ sudo GOPATH=/opt/go_pkgs  CC='gcc -m64' CGO_CFLAGS='-m64' CGO_LDFLAGS='-m64' GOARCH=sparc64 CGO_ENABLED=1 go install -x -gccgoflags=-m64

WORK=/tmp/go-build365019570

mkdir -p $WORK/b001/

cd $WORK

/usr/gnu/bin/gccgo -fgo-importcfg=/dev/null -c -x c - || true

cd /opt/go_pkgs/src/github.com/golang/glog

/usr/gnu/bin/gccgo -c -g -fdebug-prefix-map=$WORK=/tmp/go-build -gno-record-gcc-switches -fgo-pkgpath=github.com/golang/glog -o $WORK/b001/_go_.o -I $WORK/b001/_importcfgroot_ -m64 ./glog.go ./glog_file.go

echo '  .section .go.buildid,"e"' >> $WORK/b001/_buildid.s

echo '  .byte 0x79,0x71,0x58,0x37,0x74,0x64,0x76,0x6c' >> $WORK/b001/_buildid.s

echo '  .byte 0x7a,0x59,0x53,0x39,0x41,0x6a,0x30,0x58' >> $WORK/b001/_buildid.s

echo '  .byte 0x34,0x53,0x78,0x39,0x2f,0x79,0x71,0x58' >> $WORK/b001/_buildid.s

echo '  .byte 0x37,0x74,0x64,0x76,0x6c,0x7a,0x59,0x53' >> $WORK/b001/_buildid.s

echo '  .byte 0x39,0x41,0x6a,0x30,0x58,0x34,0x53,0x78' >> $WORK/b001/_buildid.s

echo '  .byte 0x39' >> $WORK/b001/_buildid.s

echo '' >> $WORK/b001/_buildid.s

/usr/gnu/bin/gccgo -xassembler-with-cpp -I $WORK/b001/ -c -o $WORK/b001/_buildid.o -D GOOS_solaris -D GOARCH_sparc64 -D GOPKGPATH=github_com_golang_glog $WORK/b001/_buildid.s

ar rcD $WORK/b001/_pkg_.a $WORK/b001/_go_.o $WORK/b001/_buildid.o

/usr/gnu/libexec/gcc/sparc-sun-solaris2.11/8.2.1/buildid -w $WORK/b001/_pkg_.a # internal

cp $WORK/b001/_pkg_.a /root/.cache/go-build/a4/a47820a6bcb6e72c26a3be36129e80b12a0f0193dd5959e2c7304a3b169d9af8-d # internal

mkdir -p /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/

cp $WORK/b001/_pkg_.a /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a

rm -r $WORK/b001/

amandeep@s113ldom1:/opt/go_pkgs/src/github.com/golang/glog$ file /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a

/opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a:     current ar archive, 32-bit symbol table

I think the problem is with the text in red. It gets the sparc64 flag, but the executable is still having 32-bit MSB relocatable SPARC
Let me know if you have any other suggestions.

[Ian Lance Taylor]

This sounds like a bug. I encourage you to file it at
https://golang.org/issue/new .

There is always the fallback of using a shell script mygcc

#!/bin/sh
exec gcc -m64 $*

and setting CC=/path/to/mygcc

Ian

[aman...@cohesity.com]

hmm...filed a bug here: https://github.com/golang/go/issues/27929

Could you explain the workaround for this again? I did not understand the fallback option.

Apart from that, I tried to run each command manually to force m64 option whenever possible. I was able to get a 64 bit executable for _buildid.o but even after that running ar rcD $WORK/b001/_pkg_.a $WORK/b001/_go_.o $WORK/b001/_buildid.o produces a 32-bit archive. Also, running buildid gives some error about 32 byte hash. Please see:

amandeep@s113ldom1:~/workspace$ /usr/gnu/libexec/gcc/sparc-sun-solaris2.11/8.2.1/buildid -w $WORK/b001/_pkg_.a

buildid: /tmp/go-build365019570/b001/_pkg_.a: cannot find 32-byte hash in id yqX7tdvlzYS9Aj0X4Sx9/yqX7tdvlzYS9Aj0X4Sx9

Let me know if any of this needs to be reported in the bug or if it provides more clarity on my situation here.

[aman...@cohesity.com]

Actually, I now understand what you meant. And even that does not work:

amandeep@s113ldom1:/opt/go_pkgs/src/github.com/golang/glog$ sudo GOPATH=/opt/go_pkgs CC='/home/amandeep/workspace/mygcc.sh' CGO_CFLAGS='-m64' CGO_LDFLAGS='-m64' GOARCH=sparc64 CGO_ENABLED=1 go install -x -gccgoflags=-m64

WORK=/tmp/go-build445938530

mkdir -p $WORK/b001/

cd $WORK

/usr/gnu/bin/gccgo -fgo-importcfg=/dev/null -c -x c - || true

cd /opt/go_pkgs/src/github.com/golang/glog

/usr/gnu/bin/gccgo -c -g -fdebug-prefix-map=$WORK=/tmp/go-build -gno-record-gcc-switches -fgo-pkgpath=github.com/golang/glog -o $WORK/b001/_go_.o -I $WORK/b001/_importcfgroot_ -m64 ./glog.go ./glog_file.go

echo '  .section .go.buildid,"e"' >> $WORK/b001/_buildid.s

echo '  .byte 0x79,0x71,0x58,0x37,0x74,0x64,0x76,0x6c' >> $WORK/b001/_buildid.s

echo '  .byte 0x7a,0x59,0x53,0x39,0x41,0x6a,0x30,0x58' >> $WORK/b001/_buildid.s

echo '  .byte 0x34,0x53,0x78,0x39,0x2f,0x79,0x71,0x58' >> $WORK/b001/_buildid.s

echo '  .byte 0x37,0x74,0x64,0x76,0x6c,0x7a,0x59,0x53' >> $WORK/b001/_buildid.s

echo '  .byte 0x39,0x41,0x6a,0x30,0x58,0x34,0x53,0x78' >> $WORK/b001/_buildid.s

echo '  .byte 0x39' >> $WORK/b001/_buildid.s

echo '' >> $WORK/b001/_buildid.s

/usr/gnu/bin/gccgo -xassembler-with-cpp -I $WORK/b001/ -c -o $WORK/b001/_buildid.o -D GOOS_solaris -D GOARCH_sparc64 -D GOPKGPATH=github_com_golang_glog $WORK/b001/_buildid.s

ar rcD $WORK/b001/_pkg_.a $WORK/b001/_go_.o $WORK/b001/_buildid.o

/usr/gnu/libexec/gcc/sparc-sun-solaris2.11/8.2.1/buildid -w $WORK/b001/_pkg_.a # internal

cp $WORK/b001/_pkg_.a /root/.cache/go-build/a4/a47820a6bcb6e72c26a3be36129e80b12a0f0193dd5959e2c7304a3b169d9af8-d # internal

mkdir -p /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/

cp $WORK/b001/_pkg_.a /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a

rm -r $WORK/b001/

amandeep@s113ldom1:/opt/go_pkgs/src/github.com/golang/glog$ ls -al /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a

-rw-r--r-- 1 root root 611582 Sep 28 08:52 /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a

amandeep@s113ldom1:/opt/go_pkgs/src/github.com/golang/glog$ file /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a

/opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a:     current ar archive, 32-bit symbol table

The CC flag is not even honoured it would seem as I do not see any invocation related to mygcc.sh. Please advice.

[Ian Lance Taylor]

Do the same thing for gccgo and set the GCCGO environment variable to
that shell script.

I'm not sure what you mean by "a 32-bit archive". Is that an archive
that contains 32-bit object files? The same hack should fix that, I
hope.

Ian

[aman...@cohesity.com]

Hi Ian,

   Setting GCCGO env variable helped. I basically compiled, helloworld.go with the following options and it compiled a 64 bit exectable:

CC=/home/amandeep/workspace/mygcc.sh GCCGO=/home/amandeep/workspace/mygccgo.sh CGO_CFLAGS='-m64' CGO_LDFLAGS='-m64' GOARCH=sparc64 CGO_ENABLED=1 go build -gccgoflags=-m64 helloworld.go

amandeep@s113ldom1:~/workspace$ file helloworld

helloworld:           ELF 64-bit MSB executable SPARCV9 Version 1, dynamically linked, not stripped

However, I still can't run the executable:

amandeep@s113ldom1:~/workspace$ ./helloworld

ld.so.1: helloworld: fatal: /usr/gnu/lib/libgo.so.13: wrong ELF class: ELFCLASS32

Killed

Does it mean that I need to compile gcc from source again with 64-bit hack i.e. by running gcc configure with CC=/path/to/mygcc and recompile it?

When I said "a 32 bit archive" I meant the .a on which output of file command looks like the following:

amandeep@s113ldom1:~/workspace$ file /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a 

/opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a:     current ar archive, 32-bit symbol table 

I assumed that the error wrong ELF class: ELFCLASS32 was related to the archive created with incorrect compiler options. 

Regards,

Aman

[Ian Lance Taylor]

On Fri, Sep 28, 2018 at 5:33 PM, <aman...@cohesity.com> wrote:
> Hi Ian,
> Setting GCCGO env variable helped. I basically compiled, helloworld.go
> with the following options and it compiled a 64 bit exectable:
>
> CC=/home/amandeep/workspace/mygcc.sh
> GCCGO=/home/amandeep/workspace/mygccgo.sh CGO_CFLAGS='-m64'
> CGO_LDFLAGS='-m64' GOARCH=sparc64 CGO_ENABLED=1 go build -gccgoflags=-m64
> helloworld.go
>
> amandeep@s113ldom1:~/workspace$ file helloworld
> helloworld: ELF 64-bit MSB executable SPARCV9 Version 1,
> dynamically linked, not stripped
>
> However, I still can't run the executable:
> amandeep@s113ldom1:~/workspace$ ./helloworld
> ld.so.1: helloworld: fatal: /usr/gnu/lib/libgo.so.13: wrong ELF class:
> ELFCLASS32
> Killed
>
> Does it mean that I need to compile gcc from source again with 64-bit hack
> i.e. by running gcc configure with CC=/path/to/mygcc and recompile it?

You'll need to set LD_LIBRARY_PATH to point to the directory with your
64-bit libgo.so.

> When I said "a 32 bit archive" I meant the .a on which output of file
> command looks like the following:
> amandeep@s113ldom1:~/workspace$ file
> /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a
> /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a:
> current ar archive, 32-bit symbol table
>
> I assumed that the error wrong ELF class: ELFCLASS32 was related to the
> archive created with incorrect compiler options.

Pedantically speaking, this is about the objects in the archive, not
the archive itself.

Ian

[aman...@cohesity.com]

Thanks. I found that on Solaris 11 the 64 bit libs are generated under /usr/gnu/lib/64 when gcc was configured with --prefix= /usr/gnu. Everything works on Solaris 11. However, I am facing problems on Solaris 10 as it seems there are no 64-bit libs generated there. I will ask another question if I can't seem to find a way.

Thanks so much for helping out on this.