Clang linking error when using library redis++

Question

I am using Windos 10, Clang 11.0 installed from Visual Studio installer. I want to use library redis++, so I first installed library hiredis (I built it with selecting toolset "cmake -T ClangCL ...") and then installed redis++ with similar cmake command.

My CMakeLists.txt file for simple test project looks like this:

cmake_minimum_required(VERSION 3.18)
project(HELLO)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

add_executable(target hello.cpp)

find_package(hiredis)
target_include_directories(target PUBLIC ${HIREDIS_HEADER})
target_link_libraries(target ${HIREDIS_LIB})

find_package(redis++)
target_include_directories(target PUBLIC ${REDIS_PLUS_PLUS_HEADER})
target_link_libraries(target ${REDIS_PLUS_PLUS_LIB})

hello.cpp looks like:

#include <sw/redis++/redis++.h>

using namespace sw::redis;

in main(int argc, char *argv[]){
    auto redis = Redis("tcp://127:0:0:1:6379");
    const sw::redis::StringView key = "test";
    redis.rpop(key);

    return 0;
}

When I build the project, I get error lld-link error: undefined symbol sw::redis::Redis::rpop. If I just call redis.pop() (without passing argument), I get too few arguments to function call.

So I am not really sure what is going on, if I call rpop() in invalid way, it sees the function signature and tells me I need to pass an argument, but when I pass it, it says linking error.

score 1 · Accepted Answer · answered Dec 09 '22 at 17:51

Successful call to

find_package(redis++)

creates IMPORTED targets redis++::redis++ for the shared library and redis++::redis++_static for the static library. For use Redis++ you need to link one of these targets into the executable:

target_link_libraries(target redis++::redis++)

(Linkage with the IMPORTED target automatically sets include directories, so the call to target_include_directories is not needed.)

The approach with using variables REDIS_PLUS_PLUS_HEADER and REDIS_PLUS_PLUS_LIB works if you set these variables in corresponding find_path and find_library calls, as described in their docs: https://github.com/sewenew/redis-plus-plus#build-with-cmake.

As with any other project, find_package approach (described at the beginning of that post) is always a preferred way.

Thank you. I fixed the code but is still isn't compiling with Clang, while with MSVC it does compile. So I imagine the problem must be somewhere else. — user3007875, Dec 13 '22 at 13:10

Clang linking error when using library redis++

1 Answers1