我正在尝试使用 SDL 和 C++ 制作游戏。
到目前为止,我还不能对此做任何事情。我遵循了 Mac 的所有说明(我有一个 Mac v. 10.12.2)和 g++ on http://www.lazyfoo.net/tutorials/SDL/01_hello_SDL/index.php .
现在,我遇到链接器错误,提示无法找到 -l(小写 L)选项指定的库。这是我的 Makefile:
CC = g++
CFLAGS = -g -Wall -std=c++11
SDL_PATH = /Users/myname/Documents/Code-Libraries/SDL2-2.0.5
SDL_INCLUDE = -I$(SDL_PATH)/include
SDL_LIB = -L$(SDL_PATH) -l/usr/local/lib/libSDL2.a
default: SDL01
SDL01: 01_hello_SDL.cpp
$(CC) $(CFLAGS) 01_hello_SDL.cpp $(SDL_LIB) $(SDL_INCLUDE) -o SDL01
clean:
rm -f SDL01 *.o
我试过 -lSDL2。我试过-lSDL。我试过-l/usr/local/lib/libSDL2.a。我只尝试了 -L 选项(没有 -l 选项),用各种方式编写/Users/myname/Documents/Code-Libraries/SDL2-2.0.5 和这个(/Users/myname/Documents/Code-Libraries/SDL2-2.0.5) 给了我...
Undefined symbols for architecture x86_64:
"_SDL_CreateWindow", referenced from:
_main in 01_hello_SDL-f65b5c.o
"_SDL_Delay", referenced from:
_main in 01_hello_SDL-f65b5c.o
"_SDL_DestroyWindow", referenced from:
_main in 01_hello_SDL-f65b5c.o
"_SDL_FillRect", referenced from:
_main in 01_hello_SDL-f65b5c.o
"_SDL_GetError", referenced from:
_main in 01_hello_SDL-f65b5c.o
"_SDL_GetWindowSurface", referenced from:
_main in 01_hello_SDL-f65b5c.o
"_SDL_Init", referenced from:
_main in 01_hello_SDL-f65b5c.o
"_SDL_MapRGB", referenced from:
_main in 01_hello_SDL-f65b5c.o
"_SDL_Quit", referenced from:
_main in 01_hello_SDL-f65b5c.o
"_SDL_UpdateWindowSurface", referenced from:
_main in 01_hello_SDL-f65b5c.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [SDL01] Error 1
...而其他人告诉我他们找不到该项目的 header 。我真的迷路了,真的很想得到一些帮助。谢谢。
编辑 1:
我做了 nm/usr/local/lib/libSDL2.a | grep _SDL_CreateWindow
并得到
0000000000001cb0 T _SDL_CreateWindow
0000000000000f80 T _SDL_CreateWindowAndRenderer
0000000000007620 t _SDL_CreateWindowAndRenderer_DEFAULT
U _SDL_CreateWindowAndRenderer_REAL
0000000000001cc0 T _SDL_CreateWindowFrom
0000000000009e80 t _SDL_CreateWindowFrom_DEFAULT
U _SDL_CreateWindowFrom_REAL
0000000000009e30 t _SDL_CreateWindow_DEFAULT
U _SDL_CreateWindow_REAL
0000000000000060 T _SDL_CreateWindowAndRenderer_REAL
U _SDL_CreateWindow_REAL
U _SDL_CreateWindow_REAL
00000000000030a0 T _SDL_CreateWindowFrom_REAL
0000000000000760 t _SDL_CreateWindowTexture
0000000000002010 T _SDL_CreateWindow_REAL
U _SDL_CreateWindow_REAL
编辑 2:
这些是 ~/Documents/Code-Libraries/SDL2-2.0.5/目录中的文件/目录:
Android.mk SDL2.spec.in cmake_uninstall.cmake.in
BUGS.txt TODO.txt configure
CMakeLists.txt VisualC/ configure.in
COPYING.txt VisualC-WinRT/ debian/
CREDITS.txt VisualC.html docs/
INSTALL.txt WhatsNew.txt include/
Makefile.in Xcode/ sdl2-config.cmake.in
Makefile.minimal Xcode-iOS/ sdl2-config.in
Makefile.pandora acinclude/ sdl2.m4
Makefile.psp android-project/ sdl2.pc.in
Makefile.wiz autogen.sh src/
README-SDL.txt build/ test/
README.txt build-scripts/
SDL2.spec cmake/
最佳答案
好吧,多亏了@JohnZwinck,我才能够弄清楚我做错了什么。当告诉编译器 g++ 第三方库在哪里时,我给了它错误的位置 (-L/Users/myname/Documents/Code-Libraries/SDL2-2.0.5
) 和一个对它毫无意义的名字 (-lSDL2
)。所以我做了一些进一步的阅读,这里有一些来自 https://linux.die.net/man/1/g++ 的重要引述。 :
You can mix options and other arguments. For the most part, the order you use doesn't matter. Order does matter when you use several options of the same kind; for example, if you specify -L more than once, the directories are searched in the order specified. Also, the placement of the -l option is significant.
Linker Options
object-file-name -llibrary -nostartfiles -nodefaultlibs -nostdlib -pie -rdynamic -s -static -static-libgcc -shared -shared-libgcc -symbolic -T script -Wl,option -Xlinker option -u symbol
Directory Options
-Bprefix -Idir -iquotedir -Ldir -specs=file -I- --sysroot=dir
所以基本上,-Ldirectory 需要在 -llibrary 之前,因为 -L 选项告诉 g++ 在哪里寻找库,然后 - l 选项说明它是什么库。如果 -l 之前没有 -L,g++ 不知道从哪里寻找 -l 的库。
如果我错了,请随时纠正我!但这解决了我的问题。
关于c++ - g++ 不链接第三方库,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/42047749/