编译Stroustrup GUI库遇Polygon歧义与未定义引用问题求助

已成功安装FLTK库，单独引用#include<FL/Fl_Window.H>可正常编译，但编译Bjarne Stroustrup配套GUI库时遇到以下问题：

• 使用测试代码编译时，Polygon标识符出现歧义，冲突来自Graph_lib::Polygon与wingdi.h中的Polygon函数
• 注释using namespace Graph_lib后，Polygon歧义问题依然存在
• 注释Polygon相关代码后，出现Simple_window等符号未定义的链接错误

测试代码 #

#include "Simple_window.h" // 引入窗口库
#include "Graph.h" // 引入图形库工具
int main()
{
using namespace Graph_lib; // 图形工具位于Graph_lib命名空间
Point tl {100,100}; // 窗口左上角坐标
Simple_window win {tl,600,400,"Canvas"}; // 创建窗口
Polygon poly; // 创建多边形形状
poly.add(Point{300,200}); // 添加顶点
poly.add(Point{350,100}); // 添加顶点
poly.add(Point{400,200}); // 添加顶点
poly.set_color(Color::red); // 设置多边形颜色
win.attach (poly); // 将多边形绑定到窗口
win.wait_for_button(); // 等待用户点击按钮
}

编译含Polygon代码时的错误信息 #

C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\Test_output.cpp: In function 'int main()':
    C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\Test_output.cpp:8:5: error: reference to 'Polygon' is ambiguous
        8 |     Polygon poly; // make a shape (a polygon)
          |     ^~~~~~~
    In file included from C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\GUI.h:11,
                     from C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\Simple_window.h:2,
                     from C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\Test_output.cpp:1:
    C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\Graph.h:248:8: note: candidates are: 'struct Graph_lib::Polygon'
      248 | struct Polygon : Closed_polyline {      // closed sequence of non-intersecting lines
          |        ^~~~~~~
    In file included from C:/msys64/mingw64/include/windows.h:71,
                     from C:/msys64/mingw64/include/FL/Fl_Window.H:26,
                     from C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\Window.h:5,
                     from C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\GUI.h:10:
    C:/msys64/mingw64/include/wingdi.h:3467:28: note:                 'WINBOOL Polygon(HDC, const POINT*, int)'
     3467 |   WINGDIAPI WINBOOL WINAPI Polygon(HDC hdc,CONST POINT *apt,int cpt);
          |                            ^~~~~~~
    C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\Test_output.cpp:9:5: error: 'poly' was not declared in this scope
        9 |     poly.add(Point{300,200}); // add a point

注释using namespace Graph_lib后的错误信息 #

C:\msys64\mingw64\bin\g++.exe -fdiagnostics-color=always -g C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\Test_output.cpp -lfltk -o C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\Test_output.exe
C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\Test_output.cpp: In function 'int main()':
C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\Test_output.cpp:8:5: error: reference to 'Polygon' is ambiguous
    8 |     Polygon poly; // make a shape (a polygon)
      |     ^~~~~~~
In file included from C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\GUI.h:11,
                 from C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\Simple_window.h:2,
                 from C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\Test_output.cpp:1:
C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\Graph.h:248:8: note: candidates are: 'struct Graph_lib::Polygon'
  248 | struct Polygon : Closed_polyline {      // closed sequence of non-intersecting lines
      |        ^~~~~~~
In file included from C:/msys64/mingw64/include/windows.h:71,
                 from C:/msys64/mingw64/include/FL/Fl_Window.H:26,
                 from C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\Window.h:5,
                 from C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\GUI.h:10:
C:/msys64/mingw64/include/wingdi.h:3467:28: note:                 'WINBOOL Polygon(HDC, const POINT*, int)'
 3467 |   WINGDIAPI WINBOOL WINAPI Polygon(HDC hdc,CONST POINT *apt,int cpt);
      |                            ^~~~~~~
C:\Users\ASUS\Desktop\C++\GUI_Train\Libs\Test_output.cpp:9:5: error: 'poly' was not declared in this scope
    9 |     poly.add(Point{300,200}); // add a point

注释Polygon后的链接错误信息 #

C:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/12.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: C:\Users\ASUS\AppData\Local\Temp\ccgW0oJL.o: in function `main':
C:\Users\ASUS\Desktop\C++\GUI_Train\Libs/Test_output.cpp:7: undefined reference to `Simple_window::Simple_window(Graph_lib::Point, int, int, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
C:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/12.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: C:\Users\ASUS\Desktop\C++\GUI_Train\Libs/Test_output.cpp:14: undefined reference to `Simple_window::wait_for_button()'
C:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/12.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: C:\Users\ASUS\AppData\Local\Temp\ccgW0oJL.o:Test_output.cp:(.rdata$_ZTV13Simple_window[_ZTV13Simple_window]+0x20): undefined reference to `Graph_lib::Window::draw()'
C:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/12.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: C:\Users\ASUS\AppData\Local\Temp\ccgW0oJL.o:Test_output.cp:(.rdata$.refptr._ZTVN9Graph_lib6ButtonE[.refptr._ZTVN9Graph_lib6ButtonE]+0x0): undefined reference to `vtable for Graph_lib::Button'
C:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/12.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: C:\Users\ASUS\AppData\Local\Temp\ccgW0oJL.o:Test_output.cp:(.rdata$.refptr._ZTVN9Graph_lib6WindowE[.refptr._ZTVN9Graph_lib6WindowE]+0x0): undefined reference to `vtable for Graph_lib::Window'

编译任务配置（VS Code tasks.json） #

{
    "tasks": [
        {
            "type": "cppbuild",
            "label": "C/C++: g++.exe build active file",
            "command": "C:\\msys64\\mingw64\\bin\\g++.exe",
            "args": [
                "-fdiagnostics-color=always",
                "-g",
                "${file}",
                "-lfltk",
                "-o",
                "${fileDirname}\\${fileBasenameNoExtension}.exe"
            ],
            "options": {
                "cwd": "${fileDirname}"
            },
            "problemMatcher": [
                "$gcc"
            ],
            "group": {
                "kind": "build",
                "isDefault": true
            },
            "detail": "Task generated by Debugger."
        }
    ],
    "version": "2.0.0"
}

问题解决方法 #

1. 消除Polygon标识符歧义 #

方案一：显式指定命名空间

直接在代码中用Graph_lib::Polygon代替Polygon，强制指定使用GUI库中的类：

Graph_lib::Polygon poly; // 显式指定命名空间，避免和Windows API的Polygon冲突

方案二：从根源屏蔽Windows API污染

在GUI库的Window.h头文件中，包含FLTK头文件前添加宏定义，禁止Windows GDI函数的声明：

#define NOGDI // 阻止wingdi.h暴露Polygon等GDI函数
#include <FL/Fl_Window.H>

2. 解决链接错误（符号未定义） #

当前编译任务仅链接了FLTK库，但未编译并链接配套GUI库的源文件。需要：

1. 从仓库中取出Graph.cpp、GUI.cpp、Window.cpp、Simple_window.cpp等配套源文件，放在测试代码同目录或指定路径
2. 修改编译任务，将这些源文件加入编译列表，同时按需添加FLTK依赖库（如fltk_images）

修改后的tasks.json示例：

{
    "tasks": [
        {
            "type": "cppbuild",
            "label": "C/C++: g++.exe build active file",
            "command": "C:\\msys64\\mingw64\\bin\\g++.exe",
            "args": [
                "-fdiagnostics-color=always",
                "-g",
                "${file}",
                "Graph.cpp",
                "GUI.cpp",
                "Window.cpp",
                "Simple_window.cpp",
                "-lfltk",
                "-lfltk_images", // 部分环境需要此库
                "-o",
                "${fileDirname}\\${fileBasenameNoExtension}.exe"
            ],
            "options": {
                "cwd": "${fileDirname}"
            },
            "problemMatcher": [
                "$gcc"
            ],
            "group": {
                "kind": "build",
                "isDefault": true
            },
            "detail": "Task generated by Debugger."
        }
    ],
    "version": "2.0.0"
}

内容的提问来源于stack exchange，提问作者Beka Tchigladze