无法获得GLFW链接

Question

我正在尝试编译以下测试程序：

#include <GL/glfw.h>

int main(int argc, char** argv) {
    if(!glfwInit()) {
        return -1;
    }

    if(!glfwOpenWindow(640, 480, 8, 8, 8, 0, 24, 0, GLFW_WINDOW)) {
        return -1;
    }

    while(glfwGetWindowParam(GLFW_OPENED)) {
        glfwSwapBuffers();
    }

    return 0;
}

但我总是得到关于GLFW功能的undefined reference错误。

下面是我的makefile：

CXX = clang++
CXXFLAGS = -Wall -std=c++0x
LDFLAGS = -lglfw

OBJ_DIR = bin
LIB_DIR = -L/usr/lib
INC_DIR = -I/usr/include

SOURCE = main.cpp
OBJECTS = ${SOURCE:%.cpp=$(OBJ_DIR)/%.o}
EXECUTABLE = hello

all: init $(OBJECTS) $(EXECUTABLE)

$(EXECUTABLE):
    $(CXX) $(CXXFLAGS) $(LDFLAGS) $(LIB_DIR) -o $@ $(OBJECTS)

$(OBJ_DIR)/%.o: %.cpp
    $(CXX) $(INC_DIR) -c $< -o $@

init:
    @mkdir -p "$(OBJ_DIR)"

clean:
    @rm -rf $(OBJ_DIR) $(EXECUTABLE)

我肯定有glfw.h和libglfw.a/.so因为当我运行locate glfw我得到：

:~$ locate glfw
/usr/include/GL/glfw.h
/usr/lib/libglfw.a
/usr/lib/libglfw.so
/usr/lib/libglfw.so.2
/usr/lib/libglfw.so.2.6

输出nm /usr/lib/libglfw.a | grep glfwInit nm /usr/lib/libglfw.a | grep glfwInit ：

:~$ nm /usr/lib/libglfw.a | grep glfwInit
                 U _glfwInitialized
                 U _glfwInitialized
                 U _glfwInitialized
                 U _glfwInitialized
0000000000000000 B _glfwInitialized
0000000000000000 T glfwInit
                 U _glfwInitialized
                 U _glfwInitialized
                 U _glfwInitialized
                 U _glfwInitialized
                 U _glfwInitialized
                 U _glfwInitJoysticks
                 U _glfwInitTimer
00000000000000c0 T _glfwInitJoysticks
0000000000000000 T _glfwInitTimer

来自clang的详细消息：

clang++ -I/usr/include -c main.cpp -o bin/main.o
clang++ -Wall -std=c++0x -Wl --verbose -lglfw -lGL -lGLU -L/usr/lib -o hello bin/main.o
Ubuntu clang version 3.0-6ubuntu3 (tags/RELEASE_30/final) (based on LLVM 3.0)
Target: x86_64-pc-linux-gnu
Thread model: posix
clang: warning: argument unused during compilation: '-std=c++0x'
 "/usr/bin/ld" -z relro --hash-style=gnu --as-needed --build-id --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o hello /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crti.o /usr/lib/gcc/x86_64-linux-gnu/4.6/crtbegin.o -L/usr/lib -L/usr/lib/gcc/x86_64-linux-gnu/4.6 -L/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu -L/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu -L/usr/lib/gcc/x86_64-linux-gnu/4.6/../../.. -L/lib/x86_64-linux-gnu -L/lib -L/usr/lib/x86_64-linux-gnu -L/usr/lib -lglfw -lGL -lGLU bin/main.o -lstdc++ -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc /usr/lib/gcc/x86_64-linux-gnu/4.6/crtend.o /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crtn.o
bin/main.o: In function `main':
main.cpp:(.text+0x17): undefined reference to `glfwInit'
main.cpp:(.text+0x76): undefined reference to `glfwOpenWindow'
main.cpp:(.text+0x97): undefined reference to `glfwGetWindowParam'
main.cpp:(.text+0xa7): undefined reference to `glfwSwapBuffers'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [hello] Error 1

好像没找到图书馆？

Answer 1

问题是glfw库是在依赖于它们的目标文件之前指定给链接器的。 ld搜索库以仅针对它正在处理的文件列表中所知的依赖关系来解析依赖关系。 因此，当ld正在搜索libglfw.a它不知道有关glfwInit在依赖main.o呢。 ld （默认情况下）不再返回搜索库。

尝试：

$(EXECUTABLE):
    $(CXX) $(CXXFLAGS) $(LIB_DIR) -o $@ $(OBJECTS)  $(LDFLAGS)

此外，库可能应在LDLIBS （或LIBS ）变量中指定 - LDFLAGS通常用于链接器选项：

CXX = clang++
CXXFLAGS = -Wall -std=c++0x
LDLIBS = -lglfw -lGL -lGLU

OBJ_DIR = bin
LIB_DIR = -L/usr/lib
INC_DIR = -I/usr/include

SOURCE = main.cpp
OBJECTS = ${SOURCE:%.cpp=$(OBJ_DIR)/%.o}
EXECUTABLE = hello

all: init $(OBJECTS) $(EXECUTABLE)

$(EXECUTABLE):
    $(CXX) $(LDFLAGS) $(LIB_DIR) -o $@ $(OBJECTS) $(LDLIBS)

$(OBJ_DIR)/%.o: %.cpp
    $(CXX) $(INC_DIR) -c $< -o $@

init:
    @mkdir -p "$(OBJ_DIR)"

clean:
    @rm -rf $(OBJ_DIR) $(EXECUTABLE)