CODEWITHSUNDEEP
cmacros
DEKKER
DEKKER

Reputation: 911

Creating macro to execute a single operation n times

In my code I often have a for loop for doing a single operation n times. E.g:

// Wait for settle
    int delayLoop = 0;
    int count = 0;
    for(delayLoop = 0; delayLoop < count; delayLoop++) {
    __NOP(); // operation to do
}

At first I wanted to make this as an function....but then I realized I do not know how to pass in the operations as a function argument.

In the above example the __NOP() is itself a macro that expands to:

__ASM volatile ("nop")

So how can I come up with a macro that I can call like this:

DO_LOOP(10, __NOP)

and what if I need to do more operations? e.g.

DO_LOOP(8, __NOP, myFunction(arg1))

that would expand to:

for(int i = 0; i < 8; i++) {
__NOP;
myFunction(arg1);
}

Upvotes: 0

Views: 350

Answers (1)

perreal
perreal

Reputation: 97948

#define DO_LOOP(x, ...) for (int i = 0; i < x; ++i) { __VA_ARGS__; } 

void f1() { printf("test\n"); }
void f2() { printf("a\n"); }   
int main()                     
{                              
  DO_LOOP(10, f1(), f2());     
  return 0;                    
}

gcc -E test.c:

void f1() { printf("test\n"); }
void f2() { printf("a\n"); }
int main()
{
  for (int i = 0; i < 10; ++i) { f1(), f2(); };
  return 0;
}

This doesn't work with inline assembly though. You can do something like:

#define DO2(x, a, b) for (int i = 0; i < x; ++i) { a; b;}

and use:

DO2(10, __NOP(), f1());

Upvotes: 1

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