Linking libc++ to CMake project on Linux

Question

I want to use libc++ together with clang on Arch Linux in CMake project. I installed libc++ and added following lines to CMakeLists.txt as said on LLVM site in Linux section of "Using libc++ in your programs":

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -stdlib=libc++")
set(CMAKE_EXE_LINKER_FLAGS "-lc++abi")

I have tried just "++abi" in linker's flags, but it didn't help. I need some help in figuring out what i should write in my CMakeLists.txt.

@RichardHodges CMake doesn't give any error messages, but when I try to use std::string for example, clang gives me following message: `implicit instantiation of undefined template 'std::__l::basic_string, std::__1::allocator>'` — Ostrea, Nov 28 '14 at 10:07
@RichardHodges I did, and when i use libstdc++ everything works just fine — Ostrea, Nov 28 '14 at 11:05
@RichardHodges how can i do it in CMake? I tried to use CMAKE_EXE_LINKER_FLAGS as shown in my question, but it didn't help — Ostrea, Nov 28 '14 at 13:42
try this: `set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -lc++ -lc++abi")` — Richard Hodges, Nov 28 '14 at 17:41

score 32 · Accepted Answer · edited Sep 12 '18 at 20:44

32

Don't forget to set the compiler to clang++:

set(CMAKE_CXX_COMPILER "clang++")

Also, purge the cmake generated files (delete the folder CMakeFiles and CMakeCache.txt).

Depending on your system, it might also help to set

set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -stdlib=libc++ -lc++abi")

edited Sep 12 '18 at 20:44

xaxxon

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answered Feb 04 '15 at 05:25

emw

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Hmm, I get an error: The CMAKE_CXX_COMPILER: clang++ is not a full path and was not found in the PATH. Tell CMake where to find the compiler by setting either the environment variable "CXX" or the CMake cache entry CMAKE_CXX_COMPILER to the full path to the compiler, or to the compiler name if it is in the PATH. Not a big deal, I can set the compiler in the configuration. (I _don’t_ want to set the whole path.) – Flash Sheridan Oct 24 '18 at 19:49
I tried this method but still with linking error, complaining std::cout is undefined reference. – ChrisZZ Jun 12 '21 at 05:40

score 2 · Answer 2 · answered Jul 20 '20 at 19:10

The "proper" way to do this in CMake at the moment, until a specific base feature is added to switch standard libraries that is, is to use a toolchain file.

In that toolchain file you specify the compiler etc similarly to the other answers here.

BUT what's great about toolchains is they can be swapped out quickly either on the commandline (using -DCMAKE_TOOLCHAIN_FILE=path/to/file) OR in VSCode with CMakeTools extension installed, and probably other editors too.

But having to hand code your own toolchain files is yet another obscure chore! No fun!

Luckily, I stumbled upon this github that maintains a suite of them so you don't have to write them from scratch! Should be a lot less likely to get them wrong.

https://github.com/ruslo/polly

Linking libc++ to CMake project on Linux

2 Answers2

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