"undefined reference" when linking C-library using gccgo

[fredrik.pe...@gmail.com]

Hello everyone!

Today I encountered what seems to be a bug in gccgo.

What I'm trying to do is to link and use a C-library in my application written in Go. I have narrowed the C-library down to having a method printing "hi" on stdio.

The directory structure is:

$ tree cfuncer ccombo

cfuncer

├── inc

│   └── cfuncer.h

├── libcfunker.a

└── src

    └── cfuncer.c

ccombo

└── ccombo.go

The main Go-program looks like:

http://play.golang.org/p/h9cXKM6WzG

the C-library consists of the following code:

http://play.golang.org/p/BIVXB0wZjg

and is compiled in the following way:

$ cd cfunker

$ gcc -I inc -Wall -c cfuncer.c

$ ar cruv libcfuncer.a cfuncer.o

Compiling the main program as:

$ cd ../ccombo

$ go build main.go

works, but when using gccgo like:

$ go build -compiler=gccgo main.go

it fails with the error:

# command-line-arguments

/tmp/go-build937064904/command-line-arguments/_obj/ccombo.cgo2.o: In function `_cgo_53b96737dc38_Cfunc_cfunction':

ccombo.cgo2.c:(.text+0x3): undefined reference to `cfunction'

collect2: error: ld returned 1 exit status

My compilers has the following versions:

$ go version

go version go1.2 linux/amd64

$ gccgo -v

Using built-in specs.

COLLECT_GCC=gccgo

COLLECT_LTO_WRAPPER=/opt/gccgo-stable/libexec/gcc/x86_64-unknown-linux-gnu/4.8.2/lto-wrapper

Target: x86_64-unknown-linux-gnu

Configured with: ../gcc-4.8.2/configure --prefix=/opt/gccgo-stable --enable-languages=c,c++,go

Thread model: posix

gcc version 4.8.2 (GCC)

I have also tried to do the same compilation with gcc 4.9.0 but it produces the same error.

$ gccgo -v

Using built-in specs.

COLLECT_GCC=/opt/gccgo/bin/gccgo

COLLECT_LTO_WRAPPER=/opt/gccgo/libexec/gcc/x86_64-unknown-linux-gnu/4.9.0/lto-wrapper

Target: x86_64-unknown-linux-gnu

Configured with: ../gcc/configure --prefix=/opt/gccgo --with-arch-32=i586 --enable-languages=c,c++,go

Thread model: posix

gcc version 4.9.0 20131127 (experimental) (GCC)

-- 

Fredrik Pettersson

[Ian Lance Taylor]

On Fri, Mar 14, 2014 at 3:53 AM, <fredrik.pe...@gmail.com> wrote:
>
> Today I encountered what seems to be a bug in gccgo.

Is this http://golang.org/issue/7303 ?

Ian

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[fredrik.pe...@gmail.com]

On Friday, March 14, 2014 2:42:43 PM UTC+1, Ian Lance Taylor wrote:

On Fri, Mar 14, 2014 at 3:53 AM,  <fredrik.pe...@gmail.com> wrote:
>
> Today I encountered what seems to be a bug in gccgo.


Is this http://golang.org/issue/7303 ?

I recompiled my gcc today and gccgo now has version 4.9.0 20140307. 

Since the issue was solved March 12 it is not possible for me to try the fix with my compiler (since the gofrontend is not manually merged to gcc including that commit). I Also looked through the issue and it does not seem like it is the same problem as mine.

If it helps my command-line arguments are:

$ go build -x -compiler=gccgo ccombo.go

WORK=/tmp/go-build842442322

mkdir -p $WORK/command-line-arguments/_obj/

cd /home/fredpe/src/goprogs/src/ccombo

/home/fredpe/src/go/pkg/tool/linux_amd64/cgo -objdir $WORK/command-line-arguments/_obj/ -gccgo -- -I $WORK/command-line-arguments/_obj/ -I ../cfunker/inc/ ccombo.go

gcc -Wall -g -I $WORK/command-line-arguments/_obj/ -I /home/fredpe/src/go/pkg/linux_amd64 -o $WORK/command-line-arguments/_obj/_cgo_defun.o -D GOOS_linux -D GOARCH_amd64 -m64 -c $WORK/command-line-arguments/_obj/_cgo_defun.c

gcc -I . -g -O2 -fPIC -m64 -pthread -print-libgcc-file-name

gcc -I . -g -O2 -fPIC -m64 -pthread -I $WORK/command-line-arguments/_obj/ -I ../cfunker/inc/ -o $WORK/command-line-arguments/_obj/_cgo_main.o -c $WORK/command-line-arguments/_obj/_cgo_main.c

gcc -I . -g -O2 -fPIC -m64 -pthread -I $WORK/command-line-arguments/_obj/ -I ../cfunker/inc/ -o $WORK/command-line-arguments/_obj/_cgo_export.o -c $WORK/command-line-arguments/_obj/_cgo_export.c

gcc -I . -g -O2 -fPIC -m64 -pthread -I $WORK/command-line-arguments/_obj/ -I ../cfunker/inc/ -o $WORK/command-line-arguments/_obj/ccombo.cgo2.o -c $WORK/command-line-arguments/_obj/ccombo.cgo2.c

gcc -I . -g -O2 -fPIC -m64 -pthread -o $WORK/command-line-arguments/_obj/_cgo_.o $WORK/command-line-arguments/_obj/_cgo_main.o $WORK/command-line-arguments/_obj/_cgo_export.o $WORK/command-line-arguments/_obj/ccombo.cgo2.o -L ../cfunker/ -lcfunker

gccgo -I $WORK -c -g -m64 -fgo-relative-import-path=_/home/fredpe/src/goprogs/src/ccombo -o $WORK/command-line-arguments/_obj/main.o $WORK/command-line-arguments/_obj/_cgo_gotypes.go $WORK/command-line-arguments/_obj/ccombo.cgo1.go

ar cru $WORK/libcommand-line-arguments.a $WORK/command-line-arguments/_obj/main.o $WORK/command-line-arguments/_obj/_cgo_defun.o $WORK/command-line-arguments/_obj/_cgo_export.o $WORK/command-line-arguments/_obj/ccombo.cgo2.o

cd .

gccgo -o ccombo $WORK/command-line-arguments/_obj/main.o $WORK/command-line-arguments/_obj/_cgo_defun.o $WORK/command-line-arguments/_obj/_cgo_export.o $WORK/command-line-arguments/_obj/ccombo.cgo2.o -Wl,-( -m64 -lpthread -Wl,-E -Wl,-)

# command-line-arguments

/tmp/go-build842442322/command-line-arguments/_obj/ccombo.cgo2.o: In function `_cgo_ec8ce97ff4d4_Cfunc_cfunction':

ccombo.cgo2.c:(.text+0x3): undefined reference to `cfunction'

collect2: error: ld returned 1 exit status 

-- 

Fredrik Pettersson

[Ian Lance Taylor]

On Mon, Mar 17, 2014 at 3:22 AM, <fredrik.pe...@gmail.com> wrote:
>
> Since the issue was solved March 12 it is not possible for me to try the fix
> with my compiler (since the gofrontend is not manually merged to gcc
> including that commit).

That is a change to the go tool, which is not included with gccgo
anyhow.

> I Also looked through the issue and it does not seem
> like it is the same problem as mine.

That is of course possible.

Ian

[Ian Lance Taylor]

Could you open an issue for this at http://golang.org/issue/new with a
complete standalone test case? Thanks.

Ian

[fredrik.pe...@gmail.com]

On Monday, March 17, 2014 8:20:49 PM UTC+1, Ian Lance Taylor wrote:

Could you open an issue for this at http://golang.org/issue/new with a
complete standalone test case?  Thanks.

The issue is posted here: https://code.google.com/p/go/issues/detail?id=7573

Thanks for your time and help!

--

Fredrik Pettersson