Not a toughie, but I'm impatient so it's up for 250 points.
In Dev-C++, I have 2 source files and a header file in one project. At the top of both sources I have:
#include <iostream>
#include <iomanip>
#include <stdlib.h>
#include "variables.h"
Variables.h is my header file. When I try to compile, it says I have declared all my variables twice. If I remove that line from one of my sources, it will say all my variables are undefined within that source file. I'm new. This doesn't make sense. Please help.
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In the header file, declare the variables as "extern". For example:
extern int n;
This just says that they exist somewhere, but doesn't allocate storage for them.
Then make them exist somewhere: in exactly one source file, at file scope (not inside any function), define each variable. For example:
int n;
--efn
Perhaps it would help if I posted what's in variables.h:
#include <stdlib.h>
using namespace std;
extern int choice;
enum from_to { from, to };
struct history_row {
int history_from;
int history_to;
float value;
float result;
void SetValues( int from, int to, float val, float res ) {
history_from = from;
history_to = to;
value = val;
result = res;
}
};
extern history_row convert3[1000];
extern float amount;
int history_count = 0;
int *p_history = &history_count;
extern float from_rate;
extern float to_rate;
extern void main_info();
extern void init_currencies();
extern void convert();
extern void swap();
extern void setcurr(enum from_to from_or_to);
extern int history();
extern int menus(int menu);
struct curr_row {
string code;
string full;
float rate;
bool show;
void SetValues( string cod, string ful, float rat, bool sho ) {
code = cod;
full = ful;
rate = rat;
show = sho;
}
};
extern curr_row curr_table[1000];
int curr_count = 9;
int convert1 = 0;
int convert2 = 1;
int *p_c1 = &convert1;
int *p_c2 = &convert2;
extern void add_cust();
extern void mod_cust();
extern void del_cust();
extern string modmenu[3];
extern string mainmenu[9];
int p=0;
extern string new_code;
extern string new_full;
extern float new_rate;
To avoid those errors, initialize variables only where they are declared. For example, in the header file:
extern int curr_count;
In the source file:
int curr_count = 9;
Structures and enumerations are types, rather than objects, so they don't need the extern keyword, and should not generate error messages about duplicate declarations. Just leave them in the header file without "extern".
--efn
Ce n'est pas logique.
The main problem I am having is the integers. It gives me a warning if I put "extern" on one, but if I remove it I get a redefinition error (obviously). The other problem is that some variables are used in both sources. This is for an assignment; my teacher will see the source and mark it down if I don't split it up into multiple sources. Is there a feasible solution?
Mais oui! The header file should have
extern int curr_count;
*Exactly one* source file should have
int curr_count = 9;
With this pattern, any file that includes the header file should be able to refer to the variable, and you should not get any warning.
Is this what you have? If so, what error or warning messages are you getting?
--efn
Business Accounts
Answer for Membership
by: AxterPosted on 2004-02-22 at 16:47:05ID: 10428624
You need to add header gaurds to your header file.