CODEWITHSUNDEEP
c
walruz
walruz

Reputation: 1329

Forbid C preprocessor to change variable's name

Here is a code example

#define S 113

double some_func1()
{
    return S;
}

double some_funcN( float S )
{
    return S/0.1;
}

When I am trying to compile it I am getting this error:

error C2143: syntax error : missing ')' before 'constant'

I am wondering if it is possible to fix it without renaming the 'S' variable?

Upvotes: 1

Views: 240

Answers (1)

dbush
dbush

Reputation: 223872

The token S will be replaced with 113 everyplace it appears. You have a few options to fix this:

  • Rename the parameter to some_funcN:

    double some_funcN( float n )
{
   return n/0.1;
}

  • Undefine the constant before the function and redefine it after. This has the disadvantage that S is defined in multiple places, so I wouldn't recommend it:

    #undef S
double some_funcN( float S )
{
   return S/0.1;
}
#define S 113

  • Change S from a macro to a variable. This allows variable scoping rules to take effect so that the function parameter S masks the definition of the variable S declared at file scope.

    const int S = 113;

Upvotes: 2

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