Multi-Argument macro definition error

Question

I defined this macro:

#define DEF_CONCAT(a, b)        a ## b
#define _internal_RCC(gpio, io) DEF_CONCAT(RCC_GPIO, gpio)
#define _internal_IO(gpio, io)  DEF_CONCAT(GPIO, io)

#define IO_CFG_OUTPUT(gpio) {rcc_periph_clock_enable(_internal_RCC(gpio));gpio_set_mode(gpio, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, _internal_IO(gpio));}

And I want to call this with:

IO_CFG_OUTPUT(LED_STATE);

LED_STATE is defined as: #define LED_STATE C,12

But when I run my program, the compiler tells me:

In file included from inc/Robot.hpp:6:0,
                 from src/Robot.cpp:1:
src/Robot.cpp: In member function 'void Robot::setup()':
inc/IODefines.hpp:13:19: error: 'C' was not declared in this scope
 #define LED_STATE C,12
                   ^

What did I do wrong?

`#define LED_STATE C,12` This seems to be wrong , what do you intend to do ? — Vinay Shukla, Aug 08 '15 at 11:48
yes, but why? It should use C as letter to combine it in IO_CFG_OUTPUT via DEF_CONCAT to RCC_GPIOC .. how? — Martin Fischer, Aug 08 '15 at 11:48
You use it also in `gpio_set_mode(gpio, ..)`, Does `C` exist ? Is `gpio_set_mode` a macro ? — Jarod42, Aug 08 '15 at 11:50
No its a function. and thanks, it shouldnt be just gpio there, was my problem, thx — Martin Fischer, Aug 08 '15 at 11:52
@MartinFischer could you explain what was wrong and how you fixed it plz — Vinay Shukla, Aug 08 '15 at 11:53
See the preprocessor output to see what the compiler sees: http://stackoverflow.com/a/277262/3425536 — Emil Laine, Aug 08 '15 at 11:55
Side note: How did you actually manage to tag this question under `macros`, yet at the same time misspell it as `makro` in the title??? — barak manos, Aug 08 '15 at 12:23
BTW, if you think the solution to your problem should be the answer you'll need to rephrase your question so that the solution becomes the answer. Then of course you can write that answer yourself. — skyking, Aug 10 '15 at 05:46

skyking · Answer 1 · 2015-08-08T12:20:22.020

Run gcc -E on the source to see what your macros expand to...

What it expands to is {rcc_periph_clock_enable(RCC_GPIOC);gpio_set_mode(C,12, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO12);};. Or with more readable formatting:

{
    rcc_periph_clock_enable(RCC_GPIOC);
    gpio_set_mode(C,12, 
                  GPIO_MODE_OUTPUT_50_MHZ, 
                  GPIO_CNF_OUTPUT_PUSHPULL, 
                  GPIO12);
};

Note the questionable practice of putting a semi-colon after the }, it could result in surprising behavior. The normal way to expand to a compound statement that works as a normal is to use do { body; } while(0)

The problem is that C is not defined anywhere.

The error message looks a bit confusing though. There's nothing formally wrong with your define directive. Whether they do what you want on the other hand I cannot tell, you should be able to tell that.

Absolutely not the solution, btw, you should read comments. it was already solved. the error was that i used gpio in gpio_set_mode instead of _internal_... — Martin Fischer, Aug 08 '15 at 18:32
Perhaps not the solution to your problem, but I think it's the answer to the actual question (ie "What did I do wrong"). There's no chance in hell to tell from the question that it should be *internal...*. — skyking, Aug 10 '15 at 05:39

Multi-Argument macro definition error

1 Answers1