[SOLVED] Comparing enum / define in keil ARM compiler

Comparing enum / define in keil ARM compiler

I'm facing difficulties to make the following conditional compilation working:

enum {  MIDI_USB_DEV_MCU_IDX, MIDI_WC_BLE_IDX, MIDI_CONN_1_IDX, MIDI_CONN_2_IDX,MIDI_IN_OUT_UARTS_NB 
};

#define MIDI_UART_IDX_TO_USE_SYSEXS      MIDI_WC_BLE_IDX

I use the following code to remind me the above define should not be used in Release mode, but the compiler does not warn on the below test.

#if MIDI_UART_IDX_TO_USE_SYSEXS != MIDI_USB_DEV_MCU_IDX
#warning MIDI_UART_IDX_TO_USE_SYSEXS must be MIDI_USB_DEV_MCU_IDX in RELEASE MODE
#endif

From what I read the enums are treated as Int, using the enum in my source works fine but the conditional compiler test fails. Any help or tip would be appreciated Thanks.

Solution

Enumeration constants do not exist in precompilation phase. Your condition expression will expand to

#if 0 != 0

Only way is to make constant work in #if expressions is to define macro constant.

#define MIDI_USB_DEV_MCU_IDX (0)
#define MIDI_WC_BLE_IDX      (1)
#define MIDI_CONN_1_IDX      (2)
#define MIDI_CONN_2_IDX      (3)
#define MIDI_IN_OUT_UARTS_NB (4)

If you are okay with compilation failing on error, then you can use enumeration constants with static assertion:

_Static_assert(
    IDI_UART_IDX_TO_USE_SYSEXS == MIDI_USB_DEV_MCU_IDX, 
    "MIDI_UART_IDX_TO_USE_SYSEXS must be MIDI_USB_DEV_MCU_IDX in RELEASE MODE");