c++ - g++ 无法找到此方法，即使它包含在内

Question

我正在使用 FANN ( http://leenissen.dk/fann/wp/download/ )。两个标题都在存档中可用，您可以在那里下载(希望我不会给您带来太多麻烦)。

/* 
 * File:   main.cpp
 * Author: johannsebastian
 *
 * Created on November 26, 2013, 8:50 PM
 */

#include "../FANN-2.2.0-Source/src/include/doublefann.h"
#include "../FANN-2.2.0-Source/src/include/fann_cpp.h"
#include <cstdlib>
#include <iostream>


using namespace std;
using namespace FANN;

/*
 * 
 */

//Remember: fann_type is double!
int main(int argc, char** argv) {
    neural_net * N = new neural_net;
    const unsigned int myLayerArray[4] = {1,2,2,1};
    const unsigned int numLayers = 4;
    N->create_standard(3,1,2,1);
    cout<<"Easy!";
    return 0;
}

g++ 说

"/usr/bin/make" -f nbproject/Makefile-Debug.mk QMAKE= SUBPROJECTS= .build-conf
make[1]: Entering directory `/home/johannsebastian/Desktop/heatmap3d/BACHnet/BACHnet'
"/usr/bin/make"  -f nbproject/Makefile-Debug.mk dist/Debug/GNU-Linux-x86/bachnet
make[2]: Entering directory `/home/johannsebastian/Desktop/heatmap3d/BACHnet/BACHnet'
mkdir -p build/Debug/GNU-Linux-x86
rm -f "build/Debug/GNU-Linux-x86/main.o.d"
g++    -c -g -MMD -MP -MF "build/Debug/GNU-Linux-x86/main.o.d" -o build/Debug/GNU-Linux-x86/main.o main.cpp
mkdir -p dist/Debug/GNU-Linux-x86
g++     -o dist/Debug/GNU-Linux-x86/bachnet build/Debug/GNU-Linux-x86/main.o 
build/Debug/GNU-Linux-x86/main.o: In function `FANN::neural_net::destroy()':
/home/johannsebastian/Desktop/heatmap3d/BACHnet/BACHnet/../FANN-2.2.0-Source/src/include/fann_cpp.h:915: undefined reference to `fann_get_user_data'
/home/johannsebastian/Desktop/heatmap3d/BACHnet/BACHnet/../FANN-2.2.0-Source/src/include/fann_cpp.h:919: undefined reference to `fann_destroy'
build/Debug/GNU-Linux-x86/main.o: In function `FANN::neural_net::create_standard_array(unsigned int, unsigned int const*)':
/home/johannsebastian/Desktop/heatmap3d/BACHnet/BACHnet/../FANN-2.2.0-Source/src/include/fann_cpp.h:979: undefined reference to `fann_create_standard_array'
collect2: error: ld returned 1 exit status
make[2]: *** [dist/Debug/GNU-Linux-x86/bachnet] Error 1
make[2]: Leaving directory `/home/johannsebastian/Desktop/heatmap3d/BACHnet/BACHnet'
make[1]: *** [.build-conf] Error 2
make[1]: Leaving directory `/home/johannsebastian/Desktop/heatmap3d/BACHnet/BACHnet'
make: *** [.build-impl] Error 2


BUILD FAILED (exit value 2, total time: 773ms)

你能帮我解决这个问题吗？我想我可能有一些基本的编译器配置错误或其他问题。

Answer 1

1. 编译器已经编译了你的代码。包括真的很有效。 (但您不必在那里指定完整路径，只需指定 header 的名称，如果库安装正确的话)。
2. 这是找不到方法的链接器(ld)。
3. 关于您是否拥有包含方法定义的库并在您调用它时将其提供给链接器(在其选项中)的链接器问题。
4. 您使用 make 文件，因此您必须指定选项(如 -lFANN)和那里的库路径(如 -L/path/path/path . 你也可以在$LD_LIBRARY_PATH 系统变量中指定路径，这样你就不需要-L 选项了)。您还必须在使用之前安装(编译)库本身。你有安装指南here .

指南对我有用:

下载 FANN-2.2.0-Source。

使用 cmake 安装它:

[08:42:24]~/Downloads$ cd FANN-2.2.0-Source/
[08:42:27]~/Downloads/FANN-2.2.0-Source$ ls
CMakeLists.txt  README.txt  bin     datasets    src
COPYING.txt VS2010      cmake       examples
[08:42:27]~/Downloads/FANN-2.2.0-Source$ cmake .
-- The C compiler identification is GNU 4.7.3
-- The CXX compiler identification is GNU 4.7.3
-- Checking whether C compiler has -isysroot
-- Checking whether C compiler has -isysroot - yes
-- Checking whether C compiler supports OSX deployment target flag
-- Checking whether C compiler supports OSX deployment target flag - yes
-- Check for working C compiler: /opt/local/bin/gcc
-- Check for working C compiler: /opt/local/bin/gcc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Checking whether CXX compiler has -isysroot
-- Checking whether CXX compiler has -isysroot - yes
-- Checking whether CXX compiler supports OSX deployment target flag
-- Checking whether CXX compiler supports OSX deployment target flag - yes
-- Check for working CXX compiler: /<...>g++
-- Check for working CXX compiler: /<...>g++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- FANN is used as APPLICATION_NAME
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/ikulakov/Downloads/FANN-2.2.0-Source
[08:43:57]~/Downloads/FANN-2.2.0-Source$ make
Scanning dependencies of target doublefann
[ 25%] Building C object src/CMakeFiles/doublefann.dir/doublefann.c.o
Linking C shared library libdoublefann.dylib
[ 25%] Built target doublefann
Scanning dependencies of target fann
[ 50%] Building C object src/CMakeFiles/fann.dir/floatfann.c.o
Linking C shared library libfann.dylib
[ 50%] Built target fann
Scanning dependencies of target fixedfann
[ 75%] Building C object src/CMakeFiles/fixedfann.dir/fixedfann.c.o
Linking C shared library libfixedfann.dylib
[ 75%] Built target fixedfann
Scanning dependencies of target floatfann
[100%] Building C object src/CMakeFiles/floatfann.dir/floatfann.c.o
Linking C shared library libfloatfann.dylib
[100%] Built target floatfann
[08:44:02]~/Downloads/FANN-2.2.0-Source$ sudo make install