Adding snappy-c to c++ project

Question

I am using cmake for the first time and was trying to add snappy-c to my c++ project. I compiled the snappy-c library using the Makefile in its repo. I was hoping that adding the snappy.o to my CMakeLists.txt would allow me to use the snappy library. Unfortunately, that gives me an undefined reference error. How can I correctly add snappy-c to my c++ project?

My directory structure is


server-side
├── src
│── common_main.cpp
├── include
└── libs/snappy-c

This is my CMakeLists.txt file

cmake_minimum_required(VERSION 3.5)

add_definitions(-std=c++11)

# include public headers
include_directories("include" ${CMAKE_CURRENT_SOURCE_DIR}/libs/snappy-c)

# recursively add .cpp files to the SOURCES variable
file(GLOB_RECURSE SOURCES "src/*.cpp" main.cpp)

# create executable using SOURCES
add_executable(common-main ${SOURCES})

target_link_libraries(
    common-main 
    ${CMAKE_CURRENT_SOURCE_DIR}/libs/snappy-c/snappy.o
)

find_library(LIBRT rt) 
   if(LIBRT)
      target_link_libraries(common-main ${LIBRT})
   endif()

The code for which I get undefined reference is

#include <iostream>
#include "snappy.h"


int main(){
   struct snappy_env env;
   snappy_init_env(&env);
}

On running make VERBOSE=1, I get the following output

cd /home/kakashi/Workbench/project/build/server-side && /usr/bin/cmake -E cmake_link_script CMakeFiles/common-main.dir/link.txt --verbose=1
/usr/bin/c++   -pthread   CMakeFiles/common-main.dir/src/common_main.cpp.o CMakeFiles/common-main.dir/src/server_service.cpp.o CMakeFiles/common-main.dir/src/service_manager.cpp.o -o common-main ../../server-side/libs/snappy.o /usr/lib/x86_64-linux-gnu/librt.so 
CMakeFiles/common-main.dir/src/common_main.cpp.o: In function `main':
common_main.cpp:(.text+0x399): undefined reference to `snappy_init_env(snappy_env*)'
collect2: error: ld returned 1 exit status
server-side/CMakeFiles/common-main.dir/build.make:200: recipe for target 'server-side/common-main' failed
make[2]: *** [server-side/common-main] Error 1
.Makefile:83: recipe for target 'all' failed
.
.
.
.

What error do you get? When you run `make VERBOSE=1`, what does your link line look like? — MadScientist, Mar 10 '21 at 00:03
```CMakeFiles/server-main.dir/src/common_main.cpp.o: In function `main': common_main.cpp:(.text+0x399): undefined reference to `snappy_init_env(snappy_env*)'``` — 0Nicholas, Mar 10 '21 at 00:29
Please edit the question to add the info: formatting in comments is difficult. I assume that symbol is defined in snappy.c. If you run `nm libs/snappy-c/snappy.o` do you see that symbol exported? You should definitely run with `VERBOSE=1` and make sure the object file appears on your link line. — MadScientist, Mar 10 '21 at 01:03
Also make sure that you are familiar with [that answer](https://stackoverflow.com/questions/12573816/what-is-an-undefined-reference-unresolved-external-symbol-error-and-how-do-i-fix/12574420#12574420) to the generic question about "undefined reference" and add to the question post relevant part of your `common_main.cpp` which calls the function. — Tsyvarev, Mar 10 '21 at 08:07
Well, does the `../../server-side/libs/snappy.o` object file contain the symbol that you're missing? I expect not. That's why you're getting this error. — MadScientist, Mar 10 '21 at 13:58

Adding snappy-c to c++ project

0 Answers0