我试图了解如何正确设置 gcc 以在环境变量中查找内容。
目前，我编译了一些代码，SDL，并将其添加到我的 .bashrc 中，并获取了该 .bashrc 。
这是一个简单的 hello 程序。
#include "SDL.h"
#include "SDL_ttf.h"
#include "SDL_image.h"
#include "SDL_mixer.h"
#include <stdlib.h>
#include <stdio.h>
SDL_Window* window;
SDL_GLContext* main_context;
int main(int argc, char** argv) {
printf("hello world %d %c \n", argc, argv[0][argc]);
if (SDL_Init(SDL_INIT_EVERYTHING) != 0) {
SDL_Log("sdl failed to core_engine_init, %s", SDL_GetError());
SDL_Quit();
return -1;
}
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK,
SDL_GL_CONTEXT_PROFILE_CORE);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
window = SDL_CreateWindow(
"title", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 300, 300,
SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN | SDL_WINDOW_RESIZABLE);
if (NULL == window) {
SDL_Log("SDL Failed to create window, %s", SDL_GetError());
SDL_Quit();
return -1;
}
main_context = SDL_GL_CreateContext(window);
if (NULL == main_context) {
SDL_Log("SDL failed to create main context, %s", SDL_GetError());
SDL_Quit();
return -1;
}
return 0;
}
尝试编译它，gcc -o main main.c我收到以下错误：
blubee$ gcc -o main main.c
/tmp/cc5hRcaO.o: In function `main':
main.c:(.text+0x3e): undefined reference to `SDL_Init'
main.c:(.text+0x47): undefined reference to `SDL_GetError'
main.c:(.text+0x59): undefined reference to `SDL_Log'
main.c:(.text+0x5e): undefined reference to `SDL_Quit'
main.c:(.text+0x77): undefined reference to `SDL_GL_SetAttribute'
main.c:(.text+0x86): undefined reference to `SDL_GL_SetAttribute'
main.c:(.text+0x95): undefined reference to `SDL_GL_SetAttribute'
main.c:(.text+0xa4): undefined reference to `SDL_GL_SetAttribute'
main.c:(.text+0xb3): undefined reference to `SDL_GL_SetAttribute'
main.c:(.text+0xd8): undefined reference to `SDL_CreateWindow'
main.c:(.text+0xf0): undefined reference to `SDL_GetError'
main.c:(.text+0x102): undefined reference to `SDL_Log'
main.c:(.text+0x107): undefined reference to `SDL_Quit'
main.c:(.text+0x11d): undefined reference to `SDL_GL_CreateContext'
main.c:(.text+0x135): undefined reference to `SDL_GetError'
main.c:(.text+0x147): undefined reference to `SDL_Log'
main.c:(.text+0x14c): undefined reference to `SDL_Quit'
collect2: error: ld returned 1 exit status
添加 SDL2 链接器标志仍然会返回错误：
blubee$ gcc -lSDL2 -o main main.c
/usr/bin/ld: cannot find -lSDL2
collect2: error: ld returned 1 exit status
这个命令编译一切都很好
blubee$ gcc -I/opt/SDL2/include/SDL2 main.c -o main -L/opt/SDL2/lib -l
SDL2
问题是我已将这些路径添加到我的 .bashrc 中，尽管我可能做得不正确。这是我的 bashrc
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/opt/SDL2/lib
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/opt/SDL_IMAGE/lib
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/opt/SDL_TTF/lib
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/opt/SDL_MIXER/lib
export LD_RUN_PATH=$LD_RUN_PATH:/opt/SDL2/lib
export LD_RUN_PATH=$LD_RUN_PATH:/opt/SDL_IMAGE/lib
export LD_RUN_PATH=$LD_RUN_PATH:/opt/SDL_TTF/lib
export LD_RUN_PATH=$LD_RUN_PATH:/opt/SDL_MIXER/lib
export C_INCLUDE_PATH=$C_INCLUDE_PATH:/opt/SDL2/include/SDL2
export C_INCLUDE_PATH=$C_INCLUDE_PATH:/opt/SDL_IMAGE/include/SDL2
export C_INCLUDE_PATH=$C_INCLUDE_PATH:/opt/SDL_TTF/include/SDL2
export C_INCLUDE_PATH=$C_INCLUDE_PATH:/opt/SDL_MIXER/include/SDL2
呼应这些环境变量表明它们在那里并且应该起作用，但事实并非如此。
我这个设置做错了什么？
答案1
您不需要任何环境变量，只需传入 SDL2 希望您使用的正确 cflags 和 ldflags 即可：
gcc main.c `pkg-config --cflags sdl2` -o main `pkg-config --libs sdl2`
或任一
gcc main.c `sdl2-config --cflags` -o main `sdl2-config --libs`
请记住：CFLAGS 位于 LDFLAGS 之前，LDFLAGS（以及带 -l 的库规范）位于最后。
SDL2 预装了 sdl2-config 脚本。您需要将 PATH 设置为它所在的目录才能成功调用它：
export PATH=/opt/SDL2/bin:$PATH
如果您直接运行每个 *-config 命令，您将看到它们只是为您输出正确的 cflags 和 ldflags。这是因为使用这些脚本的库通常比指定单个 -I/-L 参数更大，并且为它们指定单个 -I/-L 参数是不可移植的，因为将来可能会增加此类参数的数量。
并且您不应将每个包安装在其自己的目录中。例如，将所有内容安装到/usr/local例如中，那么您甚至不需要指定任何内容（大多数发行版都会/usr/local自动指向您）。