[llvm-dev] trying to get a minimal windows program linked with lld

[Shoaib Meenai via llvm-dev]

Oops; I forgot that attachments wouldn't work. https://www.dropbox.com/s/jrdbljl1q1nv5dy/kernel32.lib?dl=1

On 6/4/17, 2:46 PM, "llvm-dev on behalf of Shoaib Meenai via llvm-dev" <llvm-dev-bounces at lists.llvm.org on behalf of llvm-dev at lists.llvm.org> wrote:

    +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.
    
    From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Andrew Kelley via llvm-dev <llvm-dev at lists.llvm.org>
    Reply-To: Andrew Kelley <superjoe30 at gmail.com>
    Date: Sunday, June 4, 2017 at 1:15 PM
    To: LLVM Dev <llvm-dev at lists.llvm.org>
    Subject: Re: [llvm-dev] trying to get a minimal windows program linked with lld
    
    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.
    
    On Sun, Jun 4, 2017 at 3:33 PM, Andrew Kelley <superjoe30 at gmail.com> wrote:
    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?