Is it possible to link object files generated from the Go toolchain using clang linker (lld) ?

[Thor Odinson]

I've built an executable file using Go compiler, but the target environments loader expects the program sections to be in specific order and fails to execute.

As a result, I'm trying to compile the Go source using 'go tool compile' to generate object files, which I want to link using the clang linker option instead of 'go tool link'.

Tried building a archive/shared library using go buildmode option, but this includes lot of Go runtime in the built library. If I have to link this library along with other libraries using clang toolchain, this would not resolve the symbols as the statically built library (built using buildmode) has glibc dependency.

"

/usr/lib/llvm-5.0/bin/ld.lld: error: undefined symbol: stderr

>>> referenced by gcc_libinit.c:29

>>> 000006.o:(x_cgo_sys_thread_create) in archive ./sdlgotest.a

"

Is there a way to build Go runtime without glibc symbols, so that I can use the archive without relying on gcc toolchain ?

 

[Ian Lance Taylor]

I'm not aware of any way to do that.

The Go compiler generates a Go-specific object file format, which the
clang linker does not understand. The normal way to handle this is to
use -buildmode=c-archve, which produces an object that the clang
linker does understand; however, as you noted, that assumes that the
Go code will be linked with C code and more generally with the C
library, which I guess you don't want to do.

I'm a bit surprised that the ordinary "go build" output doesn't work
for you, as the order of sections is the default one. What section
ordering do you need?

Ian

[Thor Odinson]

Ian,

I'm bit confused with this,  

>  The normal way to handle this is to
> use -buildmode=c-archve, which produces an object that the clang
> linker does understand; however, as you noted, that assumes that the
> Go code will be linked with C code and more generally with the C
> library, which I guess you don't want to do.

Command used to build archive:

CC=clang  go build -buildmode=c-archive -o main.a main.go

I have tried with buildmode=c-archive and linking with C library only using clang toolchain.

Command used:

clang test-go.c main.a -lpthread

But, I'm getting undefined symbols from gcc_*:

ld: error: undefined symbol: stderr

>>> referenced by gcc_libinit.c:29

>>>               000006.o:(x_cgo_sys_thread_create) in archive main.a

>>> referenced by gcc_fatalf.c:17

>>>               000005.o:(fatalf) in archive main.a

>>> referenced by gcc_util.c:18

>>>               000012.o:(x_cgo_thread_start) in archive main.a

ld: error: undefined symbol: __errno_location

>>> referenced by gcc_linux_amd64.c:43

>>>               000007.o:(x_cgo_init) in archive main.a

>>> referenced by gcc_mmap.c:23

>>>               000008.o:(x_cgo_mmap) in archive main.a

>>> referenced by gcc_sigaction.c:62

>>>               000010.o:(x_cgo_sigaction) in archive main.a

clang: error: linker command failed with exit code 1 (use -v to see invocation)

Is it possible to compile the Go runtime without glibc dependency so I can use the archive with clang toolchain without relying on gcc toolchain/glibc ?

[Ian Lance Taylor]

Using -buildmode=c-archive implies a dependency on glibc.

Does it help if you use the -pthread option with clang? You should
use that option in any case.

Ian

> On Wednesday, 8 September 2021 at 01:19:50 UTC+5:30 Ian Lance Taylor wrote:
>>
>> On Tue, Sep 7, 2021 at 9:25 AM Thor Odinson
>> <thorodins...@gmail.com> wrote:
>> >
>> > I've built an executable file using Go compiler, but the target environments loader expects the program sections to be in specific order and fails to execute.
>> >
>> > As a result, I'm trying to compile the Go source using 'go tool compile' to generate object files, which I want to link using the clang linker option instead of 'go tool link'.
>> >
>> > Tried building a archive/shared library using go buildmode option, but this includes lot of Go runtime in the built library. If I have to link this library along with other libraries using clang toolchain, this would not resolve the symbols as the statically built library (built using buildmode) has glibc dependency.
>> >
>> > "
>> > /usr/lib/llvm-5.0/bin/ld.lld: error: undefined symbol: stderr
>> > >>> referenced by gcc_libinit.c:29
>> > >>> 000006.o:(x_cgo_sys_thread_create) in archive ./sdlgotest.a
>> > "
>> >
>> > Is there a way to build Go runtime without glibc symbols, so that I can use the archive without relying on gcc toolchain ?
>>
>> I'm not aware of any way to do that.
>>
>> The Go compiler generates a Go-specific object file format, which the
>> clang linker does not understand. The normal way to handle this is to
>> use -buildmode=c-archve, which produces an object that the clang
>> linker does understand; however, as you noted, that assumes that the
>> Go code will be linked with C code and more generally with the C
>> library, which I guess you don't want to do.
>>
>> I'm a bit surprised that the ordinary "go build" output doesn't work
>> for you, as the order of sections is the default one. What section
>> ordering do you need?
>>
>> Ian
>

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[Thor Odinson]

Ian,

Thanks for the clarification.

To confirm, setting go env CC=clang CXX=clang++, won't be effective for -buildmode option.