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Editorial Team
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Asked: 2026-06-13T13:34:02+00:00

I had envisaged one of these in the project preferences TESTING = HOST TESTING

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I had envisaged one of these in the project preferences

  • TESTING = HOST
  • TESTING = TARGET
  • TESTING not defined at all

My problem is with the latter.

It seems that instead of 

#if TESTING==HOST
#error "HOST defined"  // add temporarilly for testing porpoises
#endif

I need to code 

#ifdef TESTING   
#if TESTING==HOST
#error "HOST defined"  // add temporarilly for testing porpoises
#endif
#endif

I am convinced that this is not-standard behaviour, since if TESTING is not defined then it certainly doesn’t equal HOST, and I do not need that extra #ifdef TESTING with the GCC compiler.

However, when I use the Atmel AVR Studio (which I think is based on MS Visual Studio), it is necessary to add that initial #ifdef TESTING in a few dozen places 🙁

It looks like I have no choice, but I just wondered if any C standard acually requires this.

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1 Answer

  1. Editorial Team
    #if TESTING==HOST

    If TESTING is not defined, then

    it is equivalent to:

    #if 0==HOST

    From the C Standard:

    (C99, 6.10.1p4) “After all replacements due to macro expansion and the defined unary operator have been performed, all remaining identifiers (including those lexically identical to keywords) are replaced with the pp-number 0″”

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