Question

I have a function mainFunc which needs to call a several times another function process. A process has a lot of arguments but mainfunc in different calls change only two of them/ Instead of another it passes local variables which are defined and assigned before this calls to process. So I wrote a simple macro which substitutes local variables in calls to process:

#define DO_PROCESS(pred1, est1)     \
do                      \
{                       \
    process(pred1, est1, arg1, arg2, arg3); \
    ++id;                   \ 
    delete est1;                \
} while(0)

arg1, arg2, arg3 are local variables in mainFunc, so I hope my macro will just use them. In mainFunc:

int arg1, arg2, arg3;
arg1 = AssignFirst();
...
Pred* pred;
Est* est;
int estArg;
int predArg;

pred = new Pred(predArg);
DO_PROCESS(pred, new Est(estArg));
delete pred;

pred = new Pred(predArg2);
DO_PROCESS(pred, new Est(estArg2));
delete pred;

pred = new Pred(predArg3);
DO_PROCESS(pred, new Est(estArg3));
delete pred;
....

However I get C2059 and C2143 errors pointing to closing curly brace and semicolon around it respectively in last line of macro.

What’s wrong with it??

Answer 1

The most likely cause is that there’s extra whitespace after one of the backslashes in the macro definition. Make sure that \ really is the last character on a line.

Oh, and your code will leak memory, since est1 is evaluated twice in your macro definition – it expands to process(pred1, new Est(...), ...) and then later delete new Est(...), which is not what you meant. Add something like Est *e = est1; before the process call and replace the remaining occurences of est1 in your macro with e to avoid this problem.