克++未定义的引用，虽然所有的文件包括

Question

我有问题，作为++尝试我收到以下错误的对象文件链接的G：这是为什么，因为例如情况

11:29:13 **** Build of configuration Debug for project daytime **** 
make all 
'Building target: daytime' 
'Invoking: Cross G++ Linker' 
g++ -o "daytime" ./tcf/services/daytime.o ./tcf/main/main.o 
./tcf/services/daytime.o: In function `command_get_time_of_day': 
C:\Users\falkstef\runtime-EclipseApplication\daytime\Debug/../tcf/services/daytime.c:38: undefined reference to `json_read_string' 
C:\Users\falkstef\runtime-EclipseApplication\daytime\Debug/../tcf/services/daytime.c:40: undefined reference to `exception' 
C:\Users\falkstef\runtime-EclipseApplication\daytime\Debug/../tcf/services/daytime.c:43: undefined reference to `exception' 
C:\Users\falkstef\runtime-EclipseApplication\daytime\Debug/../tcf/services/daytime.c:52: undefined reference to `write_stringz' 
makefile:46: recipe for target 'daytime' failed 
C:\Users\falkstef\runtime-EclipseApplication\daytime\Debug/../tcf/services/daytime.c:54: undefined reference to `write_stringz' 
C:\Users\falkstef\runtime-EclipseApplication\daytime\Debug/../tcf/services/daytime.c:56: undefined reference to `write_errno' 
C:\Users\falkstef\runtime-EclipseApplication\daytime\Debug/../tcf/services/daytime.c:58: undefined reference to `json_write_string' 
./tcf/services/daytime.o: In function `ini_daytime_service': 
C:\Users\falkstef\runtime-EclipseApplication\daytime\Debug/../tcf/services/daytime.c:70: undefined reference to `add_command_handler' 
collect2.exe: error: ld returned 1 exit status 
make: *** [daytime] Error 1 

我不知道包括并找到#include <tcf/framework/json.h>。

没有的gcc编译相应的*.c文件，出现这个连接错误？ 这里有什么问题？

谢谢。

Answer 1

仅包含头文件是不够的;您还必须指定定义这些函数的库。

要使链接器找到所有这些方法/类（json_read_string,write_stringz, exception），您需要引用该库。如果例如它们包含在一个名为libjson.so库，你应该做的：

g++ -ljson -o "daytime" ./tcf/services/daytime.o ./tcf/main/main.o 

（或库添加到项目选项，如果Eclipse管理您的make文件）。

或者，如果它的另一个.o文件将包括在汇编（ - >或项目，如果Eclipse创建make文件）。