C++ Eclipse and CURL libraries

Sat, 21 Sep 2013 15:09:16 +0000

I’ve been working on a new C++ project with Eclipse and the CURL libraries and have been getting an undefined reference error. I use Eclipse for all my IDE needs and combined with Eclipse CDT it is great for C++ projects.

Whilst testing out the CURL libraries for my new project I encounter a problem with CURL and Eclipse and the g++ linker. When building the project you may get the following errors complaining about an undefined reference:

undefined reference to `curl_easy_init’

So first things first is to check you have the ‘libcurl4-gnutls-dev’ libraries installed if you don’t then run:

apt-get install libcurl4-gnutls-dev

Now you need to work out where the libraries are installed, curl comes with a small package to determine this so run:

curl-config --libs

This will then output commands you need to provide to the g++ linker in my case on Ubuntu 12.04 it was:

-L/usr/lib/x86_64-linux-gnu -lcurl -Wl,-Bsymbolic-functions -Wl,-z,relro

So lets add the library path to Eclipse.

Go to your project properties and then navigate to C/C++ Build -> Settings -> Cross G++ Linker -> Libraries

Click Add and put the path found with the command curl-config –libs

Now navigate to C/C++ Build -> Settings -> Cross G++ Linker -> Miscellaneous

In the Linker flags field add everything else returned by the curl-config command:

-lcurl -Wl,-Bsymbolic-functions -Wl,-z,relro

This should be it, but I encountered the same errors even after adding the libraries and flags. It turns out the command line pattern is wrong by default the flags are put straight after the g++ command. The flags in my case needed to be at the end of the g++ command.

Whilst in the project Properties navigate to C/C++ Build -> Settings -> Cross G++ Linker. The default command line pattern is

${COMMAND} ${FLAGS} ${OUTPUT_FLAG} ${OUTPUT_PREFIX}${OUTPUT} ${INPUTS}

Change this so that ${FLAGS} appears at the end:

${COMMAND} ${OUTPUT_FLAG} ${OUTPUT_PREFIX}${OUTPUT} ${INPUTS} ${FLAGS}

Now you should be able to build you C++ project with the CURL libraries from Eclipse.

TomsBlog

C++ Eclipse and CURL libraries