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,

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.

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

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?