Golang CGO Exception 0x40010006 - c++

Question

Im trying to run a function from a dll using cgo. The library is in c++ so I created a C header here are the functions defined and a .cpp file where is the implementation.
lib.h:
#ifdef __cplusplus
extern "C" {
#endif
void* LoadEngine(char*);
#ifdef __cplusplus
}
#endif
lib.cpp:
#include <Engine.h> //the library
void* LoadEngine(char *sn) {
Engine *e;
GetEngineObject(sn, &e); //function from the dll, here it fails
return (void*) e;
}
then calling it with:
package main
/*
#include "lib.h"
*/
import "C"
func main() {
e := C.LoadEngine(C.CString("foobar")
...
}
I have go1.12 windows/amd64
and mingw-w64-posix-seh
tried also mingw-w64-posix-sjlj, mingw-w64-win32-seh, mingw-w64-win32-sjlj, but the result is the same, or it doesn't compile at all
compiling it just with go build and:
#cgo windows CFLAGS: -IC:/Engine/Inc
#cgo windows CPPFLAGS: -IC:/Engine/Inc
#cgo windows LDFLAGS: -LC:/Engine/Bin64 -lEngine -lEngineObj -lole32 -loleaut32 -luuid
On win8 it runs ok, but on win10+ it doesn't work, if the function gets to calling the GetEngineObject which is from the dll, it fails with:
Exception 0x40010006 0x1 0x8deb90 0x7ffbc9ada388
PC=0x7ffbc9ada388
runtime: unknown pc 0x7ffbc9ada388
stack: frame={sp:0x8dea80, fp:0x0} stack=[0x0,0x8dfdf0)
00000000008de980: 0000000002000002 000000002a080321
00000000008de990: 0000000090000191 0000000000000321
00000000008de9a0: 0000000500000008 0000000500000000
00000000008de9b0: feeefeeefeeefeee 00000000024c0150
00000000008de9c0: 0000000000000000 0000000000000000
00000000008de9d0: 00000000024c0000 00007ffbccb730ac
00000000008de9e0: 0000000002680000 00000000024c1e30
00000000008de9f0: 00000000026a2d90 00000000026ad480
00000000008dea00: 0000000000000df1 0000000000000000
00000000008dea10: 0000000000000df1 0000000000000df1
00000000008dea20: 0000000000001bf8 0000000000000000
00000000008dea30: 0000000090000191 0000000000000003
00000000008dea40: 0000bcc3daf1f4cb 00000000026a2d00
00000000008dea50: 0000000000000000 000002fffb442d78
00000000008dea60: 0000000000000000 00000000008dfb00
00000000008dea70: 0000000000000020 00007ffbc9ada388
00000000008dea80: <00000000024c0000 000000002fbe1490
00000000008dea90: 00000000008df970 00000000ffffffff
00000000008deaa0: 0000000040010006 0000000000000000
00000000008deab0: 00007ffbc9ada388 0000000000000002
00000000008deac0: 0000000000000001 00000000008deb90
00000000008dead0: 00000000001b0150 0000000000800000
00000000008deae0: 00000000026ad480 0000000000000000
00000000008deaf0: 00000000001b10b0 0000000000690000
00000000008deb00: 00000000024c0000 00007ffbccbbcafa
00000000008deb10: 00000000024c0000 00007ffbccb76ff8
00000000008deb20: 00000000026a2d90 00000000026a9c30
00000000008deb30: 0000000000000000 0000000000000001
00000000008deb40: 00002c98037a65f6 000000000000001f
00000000008deb50: 00000000026a9430 000000002fd8a367
00000000008deb60: 0000000000006000 00000000024c0000
00000000008deb70: 0000000000000df1 0000000000000000
runtime: unknown pc 0x7ffbc9ada388
stack: frame={sp:0x8dea80, fp:0x0} stack=[0x0,0x8dfdf0)
00000000008de980: 0000000002000002 000000002a080321
00000000008de990: 0000000090000191 0000000000000321
00000000008de9a0: 0000000500000008 0000000500000000
00000000008de9b0: feeefeeefeeefeee 00000000024c0150
00000000008de9c0: 0000000000000000 0000000000000000
00000000008de9d0: 00000000024c0000 00007ffbccb730ac
00000000008de9e0: 0000000002680000 00000000024c1e30
00000000008de9f0: 00000000026a2d90 00000000026ad480
00000000008dea00: 0000000000000df1 0000000000000000
00000000008dea10: 0000000000000df1 0000000000000df1
00000000008dea20: 0000000000001bf8 0000000000000000
00000000008dea30: 0000000090000191 0000000000000003
00000000008dea40: 0000bcc3daf1f4cb 00000000026a2d00
00000000008dea50: 0000000000000000 000002fffb442d78
00000000008dea60: 0000000000000000 00000000008dfb00
00000000008dea70: 0000000000000020 00007ffbc9ada388
00000000008dea80: <00000000024c0000 000000002fbe1490
00000000008dea90: 00000000008df970 00000000ffffffff
00000000008deaa0: 0000000040010006 0000000000000000
00000000008deab0: 00007ffbc9ada388 0000000000000002
00000000008deac0: 0000000000000001 00000000008deb90
00000000008dead0: 00000000001b0150 0000000000800000
00000000008deae0: 00000000026ad480 0000000000000000
00000000008deaf0: 00000000001b10b0 0000000000690000
00000000008deb00: 00000000024c0000 00007ffbccbbcafa
00000000008deb10: 00000000024c0000 00007ffbccb76ff8
00000000008deb20: 00000000026a2d90 00000000026a9c30
00000000008deb30: 0000000000000000 0000000000000001
00000000008deb40: 00002c98037a65f6 000000000000001f
00000000008deb50: 00000000026a9430 000000002fd8a367
00000000008deb60: 0000000000006000 00000000024c0000
00000000008deb70: 0000000000000df1 0000000000000000
goroutine 1 [syscall]:
path/to/package._Cfunc_LoadEngine(0x23a2c20, 0x0)
_cgo_gotypes.go:518 +0x51
path/to/package.Load(0x4d05ad, 0x1d, 0x0, 0x0, 0x0)
C:/Users/microo8/Documents/workspace/src/path/to/package/fre.go:55 +0x89
main.main()
W:/Workspace/src/path/to/package/test/test.go:12 +0x41
rax 0x3e00003e
rbx 0x2fbe1490
rcx 0xfffffffffffffffe
rdi 0xffffffff
rsi 0x8df970
rbp 0x20
rsp 0x8dea80
r8 0x2fca2793
r9 0x3a0f4c0
r10 0x2fca2701
r11 0x26aadb0
r12 0x8dfb00
r13 0x0
r14 0x2fffb442d78
r15 0x0
rip 0x7ffbc9ada388
rflags 0x202
cs 0x33
fs 0x53
gs 0x2b
I've also tried to catch the exception with mingw's __try1 and __except1 but it fails anyways. Tried different mingw versions, using -ldflags="-linkmode internal" but this doesn't compile and -ldflags="-linkmode external" makes also this exception.
EDIT: also tried to call the LoadEngine function (from lib.h) from a C program and it works fine. Compiled the lib.cpp with g++ to lib.o. And linked it to test.c where I just called the LoadEngine just from main function. So maybe there is something wrong how go links the library to cgo?

Answer 1

For some reason on win10+ it would raise the DBG_PRINTEXCEPTION_C. Which is caused by the OutputDebugStringW and no debugger is listening.
I think normally it would be done with microsoft's __try and __except, but in MinGW is just __try1 and __except1, which I think only works on 32bit systems (very little documentation is to that)
But I found, that you can add a Exception Handler
so now lib.cpp:
#include <Engine.h> //the library
#ifdef _WIN32
#include <windows.h>
LONG WINAPI VectoredHandler(struct _EXCEPTION_POINTERS *ExceptionInfo) {
UNREFERENCED_PARAMETER(ExceptionInfo);
return EXCEPTION_CONTINUE_EXECUTION; //just continue
}
#endif
void* LoadEngine(char *sn) {
#ifdef _WIN32
PVOID handler = AddVectoredContinueHandler(1, VectoredHandler);
#endif
Engine *e;
GetEngineObject(sn, &e);
#ifdef _WIN32
RemoveVectoredContinueHandler(handler);
#endif
return (void*) e;
}
Because using the library starts with loading the engine and ends with unloading it, and the engine is a singleton, I've just made the PVOID handler also a global singleton and the AddVectoredContinueHandler is in LoadEngine and RemoveVectoredContinueHandler is in UnloadEngine.