[lld-link] LLD-LINK produces broken forward imports in source DEF

[lhmouse]

First let's define an empty DLL that exports CreateThread, forwarded from Windows KERNEL32.DLL:

// test.c
int
__stdcall
_DllMainCRTStartup(void* i, unsigned long r, void* p)
{ return 1; }

; test.def
EXPORTS
  CreateThread = kernel32.CreateThread

Now build two DLLs, one with Microsoft LINK (good.dll) and one with LLD (bad.dll):

clang test.c -Wl,-DEF:test.def -shared -Wl,-nodefaultlib -Wl,kernel32.lib -o good.dll
clang test.c -Wl,-DEF:test.def -shared -Wl,-nodefaultlib -Wl,kernel32.lib -fuse-ld=lld -o bad.dll

The bad DLL will cause failure when it's loaded by another application, saying _kernel32.dll is not found.

Now let's open the good DLL with a hex editor:

And this is the bad DLL. The import from _kernel32.CreateThread is exactly the issue.

This bug exists only when targeting x86-32.

[cjacek]

This should fix the problem: cjacek@2845c53

[lhmouse]

This should fix the problem: cjacek@2845c53

The change looks correct to me. Thanks.

[llvmbot]

@llvm/issue-subscribers-lld-coff

Author: LIU Hao (lhmouse)

First let's define an empty DLL that exports `CreateThread`, forwarded from Windows KERNEL32.DLL:

// test.c
int
__stdcall
_DllMainCRTStartup(void* i, unsigned long r, void* p)
{ return 1; }

; test.def
EXPORTS
  CreateThread = kernel32.CreateThread

Now build two DLLs, one with Microsoft LINK (good.dll) and one with LLD (bad.dll):

clang test.c -Wl,-DEF:test.def -shared -Wl,-nodefaultlib -Wl,kernel32.lib -o good.dll
clang test.c -Wl,-DEF:test.def -shared -Wl,-nodefaultlib -Wl,kernel32.lib -fuse-ld=lld -o bad.dll

The bad DLL will cause failure when it's loaded by another application, saying _kernel32.dll is not found.

Now let's open the good DLL with a hex editor:

And this is the bad DLL. The import from _kernel32.CreateThread is exactly the issue.

This bug exists only when targeting x86-32.