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Asked: 2026-05-17T17:12:04+00:00

I’ve got a list of definitions: MASTER , SLAVE0 , SLAVE1 , … SLAVE9

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I’ve got a list of definitions: MASTER, SLAVE0, SLAVE1, … SLAVE9 to control which array of audio data is programmed into a microcontroller. The micro can hold no more than one sound file, so I have included the following definitions at the top of my main.c file:

#define MASTER
#define SLAVE0
#define SLAVE1
....
#define SLAVE9

Then, I write the following in my audio array:

#if defined(MASTER)
    uint8_t sound[4096] PROGMEM = {127,126, ... }
#elif defined(SLAVE0)
    uint8_t sound[4096] PROGMEM = {126,128, ... }
....
#else 
    #ERROR "One of MASTER-SLAVE9 must be defined!"
#endif

The person wishing to compile must then go through and comment out one and only one of the #define lines. This is not only tedious, but also error-prone. So, I’m looking to simplify the process. Any pointers for any of the following tasks would be helpful:

  1. How can I test a list of macros for the presence of one and only one of these options? A simple if defined(MASTER) && !(defined(SLAVE0) || defined(SLAVE1) ...) would require 11 such tests, each with 11 subtly different conditions. It’s a one time expense, but it’s kinda ugly. It feels like this might be a common need, and that there ought to be a better way.
  2. How can I simplify the compilation process? I’ve been using AVRStudio with WinAVR t0 compile. It has an ‘export makefile’ option, but I have no experience with it. I’m stuck doing this on Windows. An ideal process would build all 11 configurations in a single command, and then I could go through and program each one to the microcontroller individually. The current, very much less-than-ideal build process involves editing the source each time I want to build, and renaming/moving the output file.
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1 Answer

  1. Editorial Team

    You can use a single test to ensure that only one of the macros is defined.

    #if (defined(MASTER) + defined(SLAVE1) + defined(SLAVE2)) != 1
    #error "Too many macros defined"
#endif

    As for the definition itself, most compilers allow you to define a macro using a command line option; this might be cleaner than a file with a “configurable options list.” You would then be able to create multiple build configurations, each of which defines a different macro, and build them each in sequence (I’m not familiar with your build system to be able to explain how exactly you need to do that).

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