trying to get a minimal windows program linked with lld

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1

Here’s some C code:

extern void *GetStdHandle(unsigned int nStdHandle);
extern void ExitProcess(unsigned int exit_code);
extern char WriteFile(void *HANDLE, const void * lpBuffer, unsigned int nNumberOfBytesToWrite,
unsigned int *lpNumberOfBytesWritten, void *lpOverlapped);

static const char *message_ptr = “hello\n”;
static const unsigned int message_len = 6;

attribute((stdcall)) int _start(void) {
void *hStdOut = GetStdHandle(-11);
WriteFile(hStdOut, message_ptr, message_len, 0, 0);
ExitProcess(0);
}

I use mingw-w64 like this:

gcc -c test.c

Create kernel32.def:

EXPORTS
ExitProcess
GetStdHandle

WriteFile

Use dlltool to create kernel32.lib:

dlltool -d kernel32.def -l kernel32.lib

Then link with lld-link:

lld-link -NOLOGO -SUBSYSTEM:console test.o kernel32.lib -OUT:test.exe -NODEFAULTLIB -ENTRY:_start

This succeeds, but then I get a segfault when running test.exe. When I step through the code, what’s happening is it’s getting to
140005068: ff 25 ce cf ff ff jmpq *-0x3032(%rip) # 0x14000203c
which is trying to jump into .idata section where presumably the stub for GetStdHandle lives. However after this jump, $rip ends up getting assigned a bogus address and then the segfault happens.

Any ideas how to make these library calls hook up correctly?

2

Update: smeenai from #llvm has been helping me with this, and we narrowed it down to kernel32.lib being no good. kernel32.lib from the 14393 SDK worked fine.

My goal is to not depend on .lib files from the SDK, so there’s still a problem to solve here.

3

+ruiu and compnerd, since there might be an lld issue here.

A slightly simpler example. This is all x86_64; I haven't tried x86.

% cat imp.c
__declspec(dllimport) void ExitProcess(unsigned exitCode);
int mainCRTStartup() { ExitProcess(0); }

% cat kernel32.def
LIBRARY kernel32
EXPORTS
  ExitProcess

% dlltool –d kernel32.def –l kernel32.lib
% cl /Zl /c imp.c
% link /subsystem:console imp.obj kernel32.lib

The above executable runs successfully, as does one compiled with ld:
% ld --version
GNU ld (GNU Binutils) 2.28
% ld imp.obj kernel32.lib

If we compile with lld, however:
% lld-link /subsystem:console /entry:mainCRTStartup imp.obj kernel32.lib

The resulting executable segfaults, and it doesn't actually have any imports:
% llvm-readobj -coff-imports imp.exe
File: imp.exe
Format: COFF-x86-64
Arch: x86_64
AddressSize: 64bit

Given that both link.exe and MinGW-w64's ld are able to handle the import
library correctly, I'm inclined to believe this is an issue with lld. I'm
attaching the kernel32.lib output by dlltool for ease of investigation.

4

Oops; I forgot that attachments wouldn't work. kernel32.lib

5

Hi Andrew,

Are you using the release version of LLD 4.0 or the SVN head? I recently made a change to the import table structure after the 4.0 release, and I’m wondering if it caused the issue.

6

I’m using the release version, but yesterday on IRC Shoaib reproduced the issue with trunk.