1) A function defined in A, how to call it in B?
If there is a header file, declare it in the header file and #include the header file in the B file.
If it is declared in the .c file, add extent declaration in B: extern void timer_hw_init(void);
2) How to call the structures and variables defined in A in B?
1> For the global structure definition, first construct the structure in the Globals.h header file, using the typedef method, such as:
typedef struct tagLineType
{
int ID;
CString Type;
double r0;
double x0;
}LINETYPE; // The name can be whatever you want, in the Globals.cpp file:
LINETYPE *lineType = NULL; // Note, initialized here
Then, go back to the Globals.h header file:
extern LINETYPE *lineType; // Note, this cannot be initialized again
2> For the definition of ordinary global variables (such as int type), first in Globals.cpp:
int iTime = -1; // note, initialized here
Then, in the Globals.h header file:
extern int iTime; // Note, can't be initialized again here
3> For global constant definitions, first in Globals.cpp:
const int UB = 10；
Then in the Globals.h header file:
extern const int UB
以上是第一种方法，是我自己总结试验成功的。用该方法定义完毕后，无论哪个.cpp文件要用到全局变量，只需在该.cpp文件中#include "Globals.h"即可，而无需再在.cpp文件中extern，所有全局变量、全局常量、全局结构体都是可见的。该方法的总体思路是，象theApp那样，在.cpp中定义，在.h头文件中extern声明。另外要注意，变量的初始化一定在Globals.cpp文件中，而不能在Globals.h头文件中。
结构体：每个用到这个全局结构体的文件都要包含typedef的头文件，声明该结构体要在.c文件中，而且不能包括在函数内。