Linking lots of .libs to make a DLL: unresolved external symbol _DllMainCRTStartup

Question

I'm performing the (terrifying) task of building LLVM 3.3 on windows and I have got to the stage where I have a load of LLVM*.lib files. I want to link them together to one huge shared DLL but am struggling (this is my first time linking stuff on windows). I've tried:

link /DLL /MACHINE:X64 /OUT:LLVM3.3.dll LLVM*.lib

but to no avail. It errors with:

LINK : warning LNK4001: no object files specified; libraries used
LINK : error LNK2001: unresolved external symbol _DllMainCRTStartup
LLVM3.3.dll : fatal error LNK1120: 1 unresolved externals

The internet suggested adding the /DEFAULTLIB:corelib switch, so I did that but again it has problems:

> link /DLL /MACHINE:X64 /DEFAULTLIB:corelibc /OUT:LLVM3.3.dll LLVM*.lib

LINK : warning LNK4001: no object files specified; libraries used
LINK : fatal error LNK1104: cannot open file 'corelibc.lib'

How do I do this?

EDIT: I managed to fix the above problem, by implementing an empty DllMain and making an EmptyDllMain.obj from it:

#include <windows.h>

BOOL APIENTRY DllMain( HANDLE hModule, 
                   DWORD  ul_reason_for_call, 
                   LPVOID lpReserved
                 )
{
    return TRUE;
}

and then trying:

link /DLL /OUT:LLVM3.3.dll LLVM*.lib EmptyDllMain.obj

but the DLL I get out is just 8kb - it seems to have missed out the many megabytes of LLVM libraries! How do I get them included?

EDIT2: I solved the LLVM compilation on Windows problem, take a look at this document on github.

The reason the DLL is tiny is that lib files are only linked in if they are needed to satisfy references. You don't have any - so nothing is linked. Options are 1. Write a DEF file to create references; 2. Use `-WHOLEARCHIVE:` — Martin Bonner supports Monica, Sep 20 '18 at 07:46

score 3 · Answer 1 · answered Aug 08 '13 at 14:45

3

I had this once while linking one lib with a wrong platform set together (X86 to X64). Make sure all the LLVM*.lib are build and linked with the correct toolchain:

[...]\Microsoft visual Studio 10.0\VC\bin\amd64\ cl.exe and link.exe

which you get by calling

"%PROGRAMFILES(X86)%\Microsoft Visual Studio 10.0\VC\vcvarsall.bat" amd64

Also I had similar problems when mixing MT and MD CRTs, I recommend you stick to

/MD (or /MDd for debug)

when compiling the objects for any of the LLVM*.lib (and any other objects from other external libraries you link into these).

[edit]

And kick out that ugly EmptyDllMain.obj !

[/edit]

answered Aug 08 '13 at 14:45

Oliver Zendel

2,695
34
29

I had the same issue and it was driving me crazy. In my case "C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\bin\vcvars32.bat" amd64_x86 was the trick to reset the toolchain. – Axel Podehl Oct 25 '18 at 16:49
"And kick out that ugly EmptyDllMain.obj " so how to solve the linker error then instead? – lalala Dec 06 '18 at 10:20

score 2 · Answer 2 · edited May 07 '15 at 20:10

2

If you manually entered the _DllMainCRTStartup, be sure you spelled it (watch case) correctly. I had _DLLMainCRTStartup and took a while to catch why I still received the linker error. For Windows CE, the required link lib is corelibc.lib.

edited May 07 '15 at 20:10

DilithiumMatrix

17,795
22
77
119

answered May 07 '15 at 19:54

Kermit Komm

21
2

Excellent answer, but what is the library for visual c++ 6.0 and below *(corelibc have an another name)* ? – user2284570 Jul 29 '15 at 20:49

score 0 · Answer 3 · answered Mar 02 '17 at 14:23

0

remove lib files from "ignore specific default libraries" from "Linker->Input" on project properties

answered Mar 02 '17 at 14:23

S.Frank Richarrd

488
1
3
15

Linking lots of .libs to make a DLL: unresolved external symbol _DllMainCRTStartup

3 Answers3