The problem is when link with LDC generate lto object, there is no export table name.

ldmd2 -mtriple=x86_64-w64-mingw32 -betterC -flto=full -c ./test.d

import ldc.attributes : assumeUsed;
import core.sys.windows.windows;
@nogc nothrow extern(C):
export int test() @assumeUsed {
        return 0;
}

export extern(Windows) BOOL DllMain(HINSTANCE hInstance, ULONG ulReason, LPVOID pvReserved) @assumeUsed {
        return true;
}

x86_64-w64-mingw32-clang -flto=full ./test.c -c

#include <windows.h>

BOOL WINAPI DllMain(HINSTANCE hinst,DWORD reason,LPVOID lpReserved)
{
	return TRUE;
}

__declspec(dllexport) int test(){
	return 0;
}

to link with lld (or use clang -L/dll -shared)

lld -flavor ld -lmsvcrt -m i386pep --shared -Bdynamic -e DllMainCRTStartup --enable-auto-image-base -o test.dll mingw/x86_64-w64-mingw32/lib/dllcrt2.o mingw/x86_64-w64-mingw32/lib/crtbegin.o -Lmingw/x86_64-w64-mingw32/lib -Lmingw/lib -Lmingw/x86_64-w64-mingw32/sys-root/mingw/lib -Lmingw/lib/clang/14.0.0/lib/windows test.o -ldnsapi -lbcrypt -lpsapi -lole32 -liphlpapi -luserenv /dll -lws2_32 -lssp_nonshared -lmingw32 mingw/lib/clang/14.0.0/lib/windows/libclang_rt.builtins-x86_64.a -lmoldname -lmingwex -ladvapi32 -lshell32 -luser32 -lkernel32 mingw/x86_64-w64-mingw32/lib/crtend.o -Bdynamic

As you can see, c and d code are same, and use same link argument. (I replace the test.o with link script to test)

If I build D code without LTO, I get the correct binary like clang dose.

Only when I build code with LDC and LTO, the problem exists:

Verify with x86_64-w64-mingw32-objdump --private-headers test.dll, you will see random symbol name for LDC & LDC bianry(some time empty).

On Sunday, 22 May 2022 at 17:06:46 UTC, Test123 wrote:

to viery this please download https://github.com/mstorsjo/llvm-mingw/releases/download/20220323/llvm-mingw-20220323-msvcrt-ubuntu-18.04-x86_64.tar.xz into linux(there is also macOS and Windows version).

test with clang:

./mingw/bin/x86_64-w64-mingw32-clang -flto=full ./test.c -c
./mingw/bin/lld -flavor ld -lmingwex -lmingw32 -lmsvcrt -lkernel32 -m i386pep --shared -Bdynamic test.o -o test.dll -e DllMainCRTStartup --enable-auto-image-base  mingw/x86_64-w64-mingw32/lib/dllcrt2.o mingw/x86_64-w64-mingw32/lib/crtbegin.o -Lmingw/x86_64-w64-mingw32/lib -Lmingw/lib -Lmingw/x86_64-w64-mingw32/sys-root/mingw/lib -Lmingw/lib/clang/14.0.0/lib/windows /dll mingw/lib/clang/14.0.0/lib/windows/libclang_rt.builtins-x86_64.a mingw/x86_64-w64-mingw32/lib/crtend.o -Bdynamic
./mingw/bin/x86_64-w64-mingw32-objdump --private-headers  ./test.dll

And you will see this at the end:

Export Table:
 DLL name: test.dll
 Ordinal base: 0
 Ordinal      RVA  Name
       0        0
       1   0x2350  test

verify with ldc

ldmd2 -mtriple=x86_64-w64-mingw32 -betterC -flto=full -c ./test.d
./mingw/bin/lld -flavor ld -lmingwex -lmingw32 -lmsvcrt -lkernel32 -m i386pep --shared -Bdynamic test.o -o test.dll -e DllMainCRTStartup --enable-auto-image-base  mingw/x86_64-w64-mingw32/lib/dllcrt2.o mingw/x86_64-w64-mingw32/lib/crtbegin.o -Lmingw/x86_64-w64-mingw32/lib -Lmingw/lib -Lmingw/x86_64-w64-mingw32/sys-root/mingw/lib -Lmingw/lib/clang/14.0.0/lib/windows /dll mingw/lib/clang/14.0.0/lib/windows/libclang_rt.builtins-x86_64.a mingw/x86_64-w64-mingw32/lib/crtend.o -Bdynamic
./mingw/bin/x86_64-w64-mingw32-objdump --private-headers  ./test.dll

you will this this at the end:

Export Table:
 DLL name: test.dll
 Ordinal base: 0
 Ordinal      RVA  Name
       0        0
       1   0x2340
       2   0x2330  t

The name for ldc2 wll be random(some time empty).

Use ldc2 without LTO always give the same result like clang.

On Sunday, 22 May 2022 at 17:27:28 UTC, Test123 wrote:

confirm with LDC 1.28.1, 1.30.0-beta1.

When you have one short export symbol LDC unlikely generate wrong result, when there is more than one export it never generate right result.

#include <windows.h>
__declspec(dllexport) int test1(){
	return 0;
}

__declspec(dllexport) int test2(){
        return 0;
}

clang wlways generate correct test.dll.

LDC give wrong result when more than one export is used with LTO:

import ldc.attributes : assumeUsed;

export extern(C) int test1() @assumeUsed {
        return 0;
}

export extern(C) int test2() @assumeUsed {
        return 0;
}

remove test1 or test2 will give you right result with LTO.

but if you use a long function name like test111242342343243243, ldc will alway give wrong result with LTO.

On Sunday, 22 May 2022 at 17:50:49 UTC, Test123 wrote:

I find a workaround, use ldc --output-ll generate ll file, then use clang build ll into object file with LTO, will fix the problem.

On Sunday, 22 May 2022 at 18:17:45 UTC, Test123 wrote:

Sadlly this will not work for a big project, cause some symbol not find problem. (not sure why)

I hope this can be fixed ASAP with the information I provide.

any suggestion will be much appreciated.

On Sunday, 22 May 2022 at 19:54:33 UTC, Test123 wrote:

Nope - MinGW isn't a supported target. Your example works fine when using the (default) MSVC target.