Is it possible to link a DLL using CGO?

[Dorival Pedroso]

Hi,

I'm wondering if we can link a go code via cgo with a dll created with mingw-gcc?

Cheers

D

[minux]

On Thu, Jan 15, 2015 at 12:35 AM, Dorival Pedroso <dorival...@gmail.com> wrote:

I'm wondering if we can link a go code via cgo with a dll created with mingw-gcc?

It's possible. Add the path to the DLL to the cgo LDFLAGS, and use cgo to

call exported function from DLL as usual.

To call integer functions from DLL, you can also use the syscall package (search for DLL

in godoc), but there are some constrains in calling functions using the syscall package

(you can't pass floating point arguments, and the stack size is limited to 64K if it's a pure

Go program), so the recommended way to use a windows DLL (no matter how it's created,

MSVC or mingw) is to use cgo.

[Dorival Pedroso]

by usual do you mean something like this?

#cgo windows LDFLAGS: -lblas -LC:\Gosl\lib\lib64\lapack_blas_windows

i'm getting errors:

$ go build

# code.google.com/p/gosl/la

c:/TDM-GCC-64/bin/../lib/gcc/x86_64-w64-mingw32/4.9.2/../../../../x86_64-w64-mingw32/bin/ld.exe: cannot find -lblas

collect2.exe: error: ld returned 1 exit status

by the way, it's win64

many thanks

d

[Dorival Pedroso]

ok, i've found one mistake: has to use forward slashes "/" 

the thing compiles but go test fails because it cannot find the dll

i suppose i have to copy this dll to the systems folder ...

thanks again

d

[minux]

On Thu, Jan 15, 2015 at 12:48 AM, Dorival Pedroso <dorival...@gmail.com> wrote:

by usual do you mean something like this?

#cgo windows LDFLAGS: -lblas -LC:\Gosl\lib\lib64\lapack_blas_windows

i'm getting errors:

$ go build

# code.google.com/p/gosl/la

c:/TDM-GCC-64/bin/../lib/gcc/x86_64-w64-mingw32/4.9.2/../../../../x86_64-w64-mingw32/bin/ld.exe: cannot find -lblas

collect2.exe: error: ld returned 1 exit status

can you link normal c programs to libblas.dll with -lblas -LC:\Gosl\lib\lib64\lapack_blas_windows?

[minux]

On Thu, Jan 15, 2015 at 12:53 AM, Dorival Pedroso <dorival...@gmail.com> wrote:

ok, i've found one mistake: has to use forward slashes "/" 

the thing compiles but go test fails because it cannot find the dll

i suppose i have to copy this dll to the systems folder ...

just put the directory containing the DLL into %PATH%, no need to copy

the DLL into system folders. 

[Dorival Pedroso]

it worked!

i've put all DLLs in C:\Gosl\lib

and added this directory to system PATH

many thanks

d

[Dorival Pedroso]

another problem: after successfully compiling and linking, i get massive errors such as "invalid runtime symbol table"

e.g.

500 SuiteSparse_start   0x563570 SuiteSparse_finish     0x563580 SuiteSparse_malloc     0x5636c0

aa0 amd_l1      0x563dd0 clear_flag.part.0      0x563e00 amd_l2 0x5655e0 amd_l_aat      0x5658b0

l_analyze       0x567390 umf_l_apply_order      0x5673e0 row_assemble   0x567600 col_assemble   0

l_extend_front  0x56b370 umf_l_free     0x56b390 umf_l_fsize    0x56b470 umfdl_garbage_collection

0x56e9b0 umfdl_local_search     0x5705c0 umfdl_lsolve   0x5707b0 umfdl_ltsolve  0x570a20 umf_l_ma

l_lhsolve       0x571570 umfdl_uhsolve  0x571980 umfdl_triplet_map_nox  0x571db0 umfdl_triplet_ma

0x574be0 umfdl_report_vector    0x574d90 umfdl_row_search       0x5758b0 umfdl_scale    0x575950

l_solve 0x579070 umfdl_start_front      0x579480 umfdl_store_lu 0x57a3e0 umfdl_symbolic_usage   0

780 umfpack_dl_col_to_triplet   0x6f6ea0 umfpack_dl_defaults    0x6f6ea8 umfpack_dl_free_numeric

[minux]

On Thu, Jan 15, 2015 at 1:31 AM, Dorival Pedroso <dorival...@gmail.com> wrote:

another problem: after successfully compiling and linking, i get massive errors such as "invalid runtime symbol table"

e.g.

500 SuiteSparse_start   0x563570 SuiteSparse_finish     0x563580 SuiteSparse_malloc     0x5636c0

aa0 amd_l1      0x563dd0 clear_flag.part.0      0x563e00 amd_l2 0x5655e0 amd_l_aat      0x5658b0

l_analyze       0x567390 umf_l_apply_order      0x5673e0 row_assemble   0x567600 col_assemble   0

l_extend_front  0x56b370 umf_l_free     0x56b390 umf_l_fsize    0x56b470 umfdl_garbage_collection

0x56e9b0 umfdl_local_search     0x5705c0 umfdl_lsolve   0x5707b0 umfdl_ltsolve  0x570a20 umf_l_ma

l_lhsolve       0x571570 umfdl_uhsolve  0x571980 umfdl_triplet_map_nox  0x571db0 umfdl_triplet_ma

0x574be0 umfdl_report_vector    0x574d90 umfdl_row_search       0x5758b0 umfdl_scale    0x575950

l_solve 0x579070 umfdl_start_front      0x579480 umfdl_store_lu 0x57a3e0 umfdl_symbolic_usage   0

780 umfpack_dl_col_to_triplet   0x6f6ea0 umfpack_dl_defaults    0x6f6ea8 umfpack_dl_free_numeric

The "invalid runtime symbol table" message originates from the Go runtime.

I have never seen this message. If you haven't modified the Go toolchain or

runtime, It might indicate a linker/runtime problem. Could you please try getting

a minimal example that still exhibit this behavior and file an issue at

https://golang.org/issue/new?

BTW, if you're not using the latest release, please try Go 1.4 first, because Go

doesn't fix bugs in releases other than the latest.

Thanks.

[Dorival Pedroso]

thank you.

i'm using go1.4.1 now

the problem persists. i'm getting this:

Exception 0xc0000005 0x0 0xd84901f6 0x6c236e50

PC=0x6c236e50

signal arrived during cgo execution

code.google.com/p/gosl/la._Cfunc_umfpack_dl_numeric(0xc08209d110, 0xc0820122a0, 0xc082012310, 0x8593f0, 0xc082036410, 0xc082036460, 0x0, 0x0)

        code.google.com/p/gosl/la/_test/_obj_test/_cgo_gotypes.go:83 +0x4b

code.google.com/p/gosl/la.(*LinSolUmfpack).Fact(0xc0820363c0, 0x0, 0x0)

        C:/Users/Dorival/Documents/MyGO/src/code.google.com/p/gosl/la/linsol_umfpack.go:190 +0xc8f

code.google.com/p/gosl/la.run_linsol_testR(0xc08205c000, 0xc0820120e0, 0x3d06849b86a12b9b, 0x3d3c25c268497682, 0xc08209d0e0, 0x5, 0x5, 0xc082021ec0, 0x5, 0x5

)

        C:/Users/Dorival/Documents/MyGO/src/code.google.com/p/gosl/la/t_linsol_test.go:31 +0x202

code.google.com/p/gosl/la.Test_linsol01(0xc08205c000)

        C:/Users/Dorival/Documents/MyGO/src/code.google.com/p/gosl/la/t_linsol_test.go:135 +0x5e1

testing.tRunner(0xc08205c000, 0x6dc980)

        c:/go/src/testing/testing.go:447 +0xc6

created by testing.RunTests

        c:/go/src/testing/testing.go:555 +0xa92

goroutine 1 [chan receive]:

testing.RunTests(0x641808, 0x6dc860, 0x25, 0x25, 0x4f95cda70b34601)

        c:/go/src/testing/testing.go:556 +0xadd

testing.(*M).Run(0xc08200a2d0, 0x6e9720)

        c:/go/src/testing/testing.go:485 +0x73

main.main()

        code.google.com/p/gosl/la/_test/_testmain.go:124 +0x1dc

goroutine 17 [syscall, locked to thread]:

runtime.goexit()

        c:/go/src/runtime/asm_amd64.s:2232 +0x1

rax     0x2ce4ae0

rbx     0x24f330

rcx     0x6c24bbb0

rdx     0x24edfc

rdi     0x2ce2be0

rsi     0x859a70

rbp     0x20

rsp     0x24ec38

r8      0x24ee00

r9      0x24ee10

r10     0x859e60

r11     0x0

r12     0x8599b0

r13     0x4

r14     0x0

r15     0x8599f0

rip     0x6c236e50

rflags  0x10202

cs      0x33

fs      0x53

gs      0x2b

exit status 2

FAIL    code.google.com/p/gosl/la       1.146s

[Dave Cheney]

At a guess your C code segfaulted.