getting errors with macros definition-c++

Question

I am getting ClassID undeclared error in the following cpp code.

    #include "stdafx.h"
    #include <iostream>
    using namespace std;
    #define RM_SESSION_MSG 0x11
    #define DECLARE_RS232_MSG(ClassID)
    enum
    {
         ID=ClassID
    }

    int main()
    {
         DECLARE_RS232_MSG(RM_SESSION_MSG)
         return 0;
    }

Johannes Schaub - litb · Accepted Answer · 2011-05-05 09:26:23Z

8

You are missing the line splice characters

#define DECLARE_RS232_MSG(ClassID) \
enum                               \
{                                  \
     ID=ClassID                    \
}

The line splice characters say that the current line and the next line are merged into a single line.

Without them, the macro definition ends at the end-of-line, so the enum in your code wasn't really part of the macro DECLARE_RS232_MSG.

You also miss a semicolon after the macro invocation in main (there needs to be a semicolon after each class or enumeration definition in C++).

answered May 5, 2011 at 9:26

Johannes Schaub - litb

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2 Comments

spandana Over a year ago

Schaub:Thanks...I did as like you told here.Got output within seconds for which i was breaking my head for hours.Thanks dude.

spandana Over a year ago

Schaub:I'm getting a warning after adding semicolon in the macro invocation as 'Declaration does not declare anything'

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