save file error！

wbgxx

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define STOP 0
#define TRUE 1
#define OK 1
#define FILE_NAME ("my.text")

typedef struct List
{
long lNum;
char cpsName[30];
long lCScore;
long lMathScore;
long atol(long i);
struct List *next;
}Stu;

Stu stuList[3] =
{
{1, "asd", 32, 44, 0},
{2, "ffg", 66, 66, 0},
{3, "dgd", 55, 44, 0},
};

Stu *CreateList()
{
Stu *head = NULL;
Stu *NewNode = NULL;
int i = 0;

for (i=0; i<3; i++)
{
	NewNode = (Stu\*)malloc(sizeof(Stu));

	NewNode->lNum = stuList\[i\].atol(stuList\[i\].lNum);
	strncpy(NewNode->cpsName, stuList\[i\].cpsName, 30);
	NewNode->lCScore = stuList\[i\].atol(stuList\[i\].lCScore);
	NewNode->lMathScore = stuList\[i\].atol(stuList\[i\].lMathScore);
	NewNode->next = NULL;

	if (NULL == head)
	{
		head = NewNode;
	}
	else
	{
		head->next = NewNode;
		head = NewNode;
	}
}

return head;

}

int SaveToFiles(Stu *head)
{
Stu *p = head;
FILE *fp;
char cFileName[1024] = {0};
//strcpy(cFileName, FILE_NAME);

if ((fp = fopen(FILE\_NAME, "wb")) == NULL)
{
	printf( "Open file error!\\n" );
	exit (1);
}

while (p != NULL)
{
	if (fwrite(p, sizeof(Stu), 1, fp) == 1)
	{
		p = p->next;
	}
	else
	{
		printf("Write file error!\\n");
		exit(1);
	}

}
fclose(fp);

printf( "Save file succeed!\\n" );
return OK;

}

int OpenFiles()
{

char cFileName\[256\] = {0};
FILE \*fp;
if (0 == (fp = fopen(FILE\_NAME, "r")))
{
	printf("Open file error!\\n");
	exit(0);
}

fgets(cFileName, 250, fp);
printf("%s", cFileName);
fclose(fp);
return OK;

}

int main()
{
Stu *head = NULL;

head = CreateList();
SaveToFiles(head);
OpenFiles();
//Print(head);

return 0;

}

this is the error information： error LNK2001: unresolved external symbol "public: long __thiscall List::atol(long)" (?atol@List@@QAEJJ@Z) Debug/file.exe : fatal error LNK1120: 1 unresolved externals Error executing link.exe.

Lost User

Firstly, do not repost the question, but edit the original. As to the error you get the statement long atol(long i); in your structure is not defined anywhere. You cannot declare a method in a structure without implementing it. You should add your own atol() method, or simply call the default library function. Also as I stated earlier your CreateList() function also has a problem.

MVP 2010 - are they mad?

wbgxx

Yeah！ fist, Createlist（）function has a problem ?why?could you give me a detail! second, I know atol()is libiary but if I use like this it also has a problem,why? thank you for your reply!

Lost User

wbgxx wrote:

I know atol()is libiary but if I use like this it also has a problem,why?

Sentences like this are rising to the top of the list of most useless statements. If your program does not work in some way, saying "it has a problem", gives us no information to guess what may be wrong. Please try and explain what happens; do you get a compiler error, does it cause an exception, does it return the wrong result, etc? However, having looked at the code again I see:

NewNode->lNum = stuList[i].atol(stuList[i].lNum);

OK, so let's correct it

NewNode->lNum = atol(stuList[i].lNum);

The atol() function takes a string of digits as input and returns its value as a long variable. Your statement is trying to pass a long as its input parameter which a) is wrong, and b) makes no sense; the value is already a long. The other problem with Createlist（） is that it returns the pointer to the last structure in your list rather than the first; you need to keep a copy of the first entry added to the head pointer.

MVP 2010 - are they mad?

enhzflep

(2) Simple - if atol is a library function then use it as such!! ;P declare your struct like this:

typedef struct List
{
long lNum;
char cpsName[30];
long lCScore;
long lMathScore;
struct List *next;
}Stu;

And use the function like this:

NewNode->lCScore = stuList[i].atol(stuList[i].lCScore);
NewNode->lCScore = atol(stuList[i].lCScore);

wbgxx

Oh!Yes,I see! very grateful for you !

Lost User

enhzflep wrote:

NewNode->lCScore = atol(stuList[i].lCScore);

Except that stuList[i].lCScore is already a long; as I pointed out in my previous message.

MVP 2010 - are they mad?

enhzflep

Yes indeed. :-O :-O

Lost User

Wish I had a £1 for every time I've done something similar :((

MVP 2010 - are they mad?