llvm dev - Dec 2012 - [LLVMdev] Errors linking against libLLVMCore

I'm trying to make a library in Xcode that links against LLVM. I used the
STL C++ template in Xcode 4.5.2, added libLLVMCore.a and libLLVMSupport.a to the
link binaries phase, and made this call in my code:

	llvm::LLVMContext& llvmCTX = llvm::getGlobalContext();

I get link errors against std::string and other STL classes:

Undefined symbols for architecture x86_64:
  "std::string::copy(char*, unsigned long, unsigned long) const",
referenced from:
      llvm::sys::Path::makeUnique(bool, std::string*) in
libLLVMSupport.a(Path.o)
  "std::string::find(char const*, unsigned long, unsigned long)
const", referenced from:
      llvm::sys::getDefaultTargetTriple() in libLLVMSupport.a(Host.o)
      .
      .
      .

Builds fine if I take out that line (the only line, so far) of LLVM code.

But code like this compiles fine:

	std::string s = "Hello world";
	std::printf("%s", s.c_str());

I figure I'm missing a lib, but I have no idea which.

TIA,

-- 
Rick

On 12/26/12 12:32 AM, Rick Mann wrote:
> I'm trying to make a library in Xcode that links against LLVM. I used
the STL C++ template in Xcode 4.5.2, added libLLVMCore.a and libLLVMSupport.a to
the link binaries phase, and made this call in my code:
>
> 	llvm::LLVMContext& llvmCTX = llvm::getGlobalContext();
>
> I get link errors against std::string and other STL classes:
>
> Undefined symbols for architecture x86_64:
>    "std::string::copy(char*, unsigned long, unsigned long)
const", referenced from:
>        llvm::sys::Path::makeUnique(bool, std::string*) in
libLLVMSupport.a(Path.o)
>    "std::string::find(char const*, unsigned long, unsigned long)
const", referenced from:
>        llvm::sys::getDefaultTargetTriple() in libLLVMSupport.a(Host.o)
>        .
>        .
>        .
>
> Builds fine if I take out that line (the only line, so far) of LLVM code.
>
> But code like this compiles fine:
>
> 	std::string s = "Hello world";
> 	std::printf("%s", s.c_str());
>
> I figure I'm missing a lib, but I have no idea which.
It is possible (but a bit unlikely) that your problem is because you're 
not linking in libstdc++.  Some C++ methods are defined in header files; 
that might explain why your simple program works but using 
libLLVMVMCore.a doesn't work.

Try using std::string::find() in your simple program and see if it 
links.  If it doesn't, then I think you just need to add -lstdc++.

-- John T.
>
> TIA,
>

On Dec 27, 2012, at 10:24 , John Criswell <criswell at illinois.edu>
wrote:
> It is possible (but a bit unlikely) that your problem is because you're
not linking in libstdc++. Some C++ methods are defined in header files; that
might explain why your simple program works but using libLLVMVMCore.a
doesn't work.
> 
> Try using std::string::find() in your simple program and see if it links. 
If it doesn't, then I think you just need to add -lstdc++.
I've been comparing how the clang++ CLI builds vs how Xcode builds. For one,
Xcode does separate clang -x c++ and clang++ (for linking) steps.

Xcode calls clang++ with -stdlib=libc++.

	http://pastebin.com/n9nCat15

Here's the output of each eith -### added (not the Xcode link step);

	http://pastebin.com/kufBknaw

-- 
Rick

On Dec 27, 2012, at 10:24 , John Criswell <criswell at illinois.edu>
wrote:
> It is possible (but a bit unlikely) that your problem is because you're
not linking in libstdc++.  Some C++ methods are defined in header files; that
might explain why your simple program works but using libLLVMVMCore.a
doesn't work.
So, you were right. Xcode was invoking the link with -stdlib=libc++, but should
have either not been passing that at all, or using -stdlib=libstdc++ (the GNU
standard library, and the default if no option is passed).
>From the description in Xcode:
libstdc++: traditional C++ standard library that works with GCC and the LLVM
Compiler (default).
libc++: highly optimized C++ standard library that works only with the LLVM
Compiler, and is designed to support new C++11 features.

Which makes me wonder why the LLVM build doesn't use the better library
(libc++). I'm assuming this is the root of the problem, that the LLVM build
used libstdc++, instead of libc++.

Can anyone clarify what's going on? Is it possible to build LLVM with
libc++? I guess to do that, it would have to be built by clang instead of GCC,
huh? Can that be done?

-- 
Rick