C++ compile-time state variables

Question

I'm interested in being able to do something like this:

 void ISR()
 {
    MEASURE_TIME(counters)
    do_something();
    MEASURE_TIME(counters)
    do_something_else();
    MEASURE_TIME(counters)
    do_another_thing();
    MEASURE_TIME(counters)
    do_one_last_thing();
    MEASURE_TIME(counters)
 }

which would somehow translate at compile time to this:

 void ISR()
 {
    counters[0] = measure_time();
    do_something();
    counters[1] = measure_time();
    do_something_else();
    counters[2] = measure_time();
    do_another_thing();
    counters[3] = measure_time();
    do_one_last_thing();
    counters[4] = measure_time();
 }

Is there a way to do maintain and increment integer state with the preprocessor (seems unlikely) or templates?

I know I can do this:

 void ISR()
 {
    int i = 0;
    counters[i++] = measure_time();
    do_something();
    counters[i++] = measure_time();
    do_something_else();
    counters[i++] = measure_time();
    do_another_thing();
    counters[i++] = measure_time();
    do_one_last_thing();
    counters[i++] = measure_time();
 }

but there's some additional value to having a compile-time index (which is difficult to explain here w/o getting into some proprietary details)

edit: this is on an embedded system, and __COUNTER__ isn't available (I just tried it: __COUNTER__ is not defined by my compiler or the preprocessor), and I'm not sure I could get Boost to work, at least not in its entirety.

See http://stackoverflow.com/questions/1132751 for preprocessor counters. — Tobias, Mar 01 '12 at 16:58
...and in fact the solution http://stackoverflow.com/a/6210155/44330 seems like it might work. — Jason S, Mar 01 '12 at 17:14

score 5 · Answer 1 · answered Mar 01 '12 at 16:58

5

__COUNTER__ macro is your friend.

answered Mar 01 '12 at 16:58

Nim

33,299
2
62
101

1

Keep in mind that Boost, for example, uses this macro, so your `__COUNTER__` may not start at 0 if you include certain headers. – Collin Dauphinee Mar 01 '12 at 17:03

score 2 · Answer 2 · answered Mar 01 '12 at 17:10

2

How about counters.push_back(measure_time()) ?

answered Mar 01 '12 at 17:10

No. I'm looking for compile-time solutions. (not to mention that STL is not available on my lowly embedded system; I'm just lucky I have C++ and templates) – Jason S Mar 01 '12 at 17:11

score 2 · Answer 3 · answered Mar 01 '12 at 17:47

2

Get boost source code. See how BOOST_PP_COUNTER works (expect to get headache). Then replicate functionality in your code. Or simply use boost. Please note that BOOST_PP_COUNTER does not use __COUNTER__.

answered Mar 01 '12 at 17:47

SigTerm

26,089
6
66
115

C++ compile-time state variables

3 Answers3