Question

I’ve tried now days to get up a libcurl sample c++ code running in Netbeans (Compiler is cygwin) on a Windows machine but it failes every time.
I’ve also searched through the web (and also through stackoverflow) but can’t find a solution… 🙁

Here is just the sample code i want to run…

#include <cstdlib>
#include <curl/curl.h>

using namespace std;

/*
 * 
 */
int main(int argc, char** argv) {
    CURL *curl;
    CURLcode res;

    curl = curl_easy_init();
    if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "http://google.com");
    res = curl_easy_perform(curl);

    curl_easy_cleanup(curl);
    }

    return 0;
}

here is the compiler result:

"/usr/bin/make" -f nbproject/Makefile-Debug.mk QMAKE= SUBPROJECTS= .build-conf
make[1]: Entering directory `/cygdrive/c/Users/Alexander/Documents/NetBeansProjects/CppApplication_3'
"/usr/bin/make"  -f nbproject/Makefile-Debug.mk dist/Debug/Cygwin_4.x_1-Windows/cppapplication_3.exe
make[2]: Entering directory `/cygdrive/c/Users/Alexander/Documents/NetBeansProjects/CppApplication_3'
mkdir -p build/Debug/Cygwin_4.x_1-Windows
rm -f build/Debug/Cygwin_4.x_1-Windows/main.o.d
g++.exe -lcurl   -c -g -MMD -MP -MF build/Debug/Cygwin_4.x_1-Windows/main.o.d -o build/Debug/Cygwin_4.x_1-Windows/main.o main.cpp
mkdir -p dist/Debug/Cygwin_4.x_1-Windows
g++.exe -lcurl    -o dist/Debug/Cygwin_4.x_1-Windows/cppapplication_3 build/Debug/Cygwin_4.x_1-Windows/main.o  
build/Debug/Cygwin_4.x_1-Windows/main.o: In function `main':
/cygdrive/c/Users/Alexander/Documents/NetBeansProjects/CppApplication_3/main.cpp:20: undefined reference to `_curl_easy_init'
/cygdrive/c/Users/Alexander/Documents/NetBeansProjects/CppApplication_3/main.cpp:22: undefined reference to `_curl_easy_setopt'
/cygdrive/c/Users/Alexander/Documents/NetBeansProjects/CppApplication_3/main.cpp:23: undefined reference to `_curl_easy_perform'
/cygdrive/c/Users/Alexander/Documents/NetBeansProjects/CppApplication_3nbproject/Makefile-Debug.mk:61: recipe for target `dist/Debug/Cygwin_4.x_1-Windows/cppapplication_3.exe' failed
make[2]: Leaving directory `/cygdrive/c/Users/Alexander/Documents/NetBeansProjects/CppApplication_3'
nbproject/Makefile-Debug.mk:58: recipe for target `.build-conf' failed
make[1]: Leaving directory `/cygdrive/c/Users/Alexander/Documents/NetBeansProjects/CppApplication_3'
/main.cpp:25: undefined reference to `_curl_easy_cleanup'
nbproject/Makefile-impl.mk:39: recipe for target `.build-impl' failed
collect2: ld returned 1 exit status
make[2]: *** [dist/Debug/Cygwin_4.x_1-Windows/cppapplication_3.exe] Error 1
make[1]: *** [.build-conf] Error 2
make: *** [.build-impl] Error 2

BUILD FAILED (exit value 2, total time: 2s)

The libcurl is also installed as a package within cygwin…
The libcurl.a is located at ‘E:\cygwin\lib’ and the cygcurl-4.dll is located at ‘E:\cygwin\bin’.

If someone could help me that would be so great!

Thanks in advance!
Regards,
Alex

Answer 1

Put the -l option at the end of your link command, like this:

g++ -o main main.o -lcurl

So in your case the output shall look like so:

g++.exe -o dist/Debug/Cygwin_4.x_1-Windows/cppapplication_3 build/Debug/Cygwin_4.x_1-Windows/main.o -lcurl

Verbatim from the gcc manual:

It makes a difference where in the command you write this [-l] option; the
linker searches and processes libraries and object files in the order
they are specified. Thus, foo.o -lz bar.o' searches libraryz’ after
file foo.o but before bar.o. If bar.o refers to functions in `z’,
those functions may not be loaded.