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extern declaration error

Aug 25, 2009 at 4:31am
paoloricardo (21)
Given the following ...

In A.CPP:

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typedef struct                  
{                               
    char author_surname[64];    
    char author_forename[64];
    char title[64];
    char isbn[20];
    char genre[MAXLENGTH+1];
    ushort radBtnCategory;
} DialogData;

Dialogdata *addBookData;


// then add data to addBookData members i.e. addBookData->author_surname etc.

I want to reference addBookData's members in B.CPP but receive this error:

In B.CPP

extern DialogData *addBookData; <======= 'Declaration syntax error'

Guidance will be welcome!
Aug 25, 2009 at 4:48am
helios (17607)
Is the declaration of DialogData available to B.cpp?
Aug 25, 2009 at 5:23am
paoloricardo (21)
helios: in what way?

I've tried putting 

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typedef struct                
{                               
    char author_surname[64];    
    char author_forename[64];
    char title[64];
    char isbn[20];
    char genre[MAXLENGTH+1];
    ushort radBtnCategory;
} DialogData;


in a header file and included that file in both A.CPP and B.CPP. That results in the same error but pointing at the A.CPP declaration

Dialogdata *addBookData;
Aug 25, 2009 at 5:33am
helios (17607)
I'm having a hard time seeing the problem. Post all three files (that is, the header, A.cpp, and B.cpp).
Aug 25, 2009 at 5:46am
paoloricardo (21)
Helios:

Original :

A.CPP
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typedef struct                  
{                               
    char author_surname[64];    
    char author_forename[64];
    char title[64];
    char isbn[20];
    char genre[MAXLENGTH+1];
    ushort radBtnCategory;
} DialogData;

Dialogdata *addBookData;


B.CPP
extern DialogData *addBookData; <==== 'Declaration syntax error'

Revised:

HEADER.H
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typedef struct                  
{                               
    char author_surname[64];    
    char author_forename[64];
    char title[64];
    char isbn[20];
    char genre[MAXLENGTH+1];
    ushort radBtnCategory;
} DialogData;


A.CPP
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#include "HEADER.H"
Dialogdata *addBookData;              <==== 'Declaration syntax error'


B.CPP
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#include "HEADER.H"
extern DialogData  *addBookData;


Thx for looking at this.
Aug 25, 2009 at 7:46am
paoloricardo (21)
I've resolved this as follows:


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HEADER.H

typedef struct                  
{                               
    char author_surname[64];    
    char author_forename[64];
    char title[64];
    char isbn[20];
    char genre[MAXLENGTH+1];
    ushort radBtnCategory;
} DialogData;

extern DialogData *addBookData;

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B.CPP

DialogData *addBookData;

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A.CPP

// no declaration of addBookData - the structure members are initialized in A.CPP


I have a successful compilation with this.
Last edited on Aug 25, 2009 at 8:05am
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