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Using C preprocessor to limit array size during compilation

Cactus Blip

Hello,

I want to use the #error directive to limit the size of a statically allocated array during compilation (it must not exceed a certain limit, and I want to fail compilation, not startup, if it is too large), but I can only work with constant expressions, of course. Is there a way to do this...?

Thanks.

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  • 0 Arm Employee Badge

    Maybe something like this is what you want:

    ... some declaration of my_array ...

#define MAX_SIZE 5000 /* bytes, for example */

typedef int dummy[sizeof(my_array) <= MAX_SIZE ? 1 : -1];

    If the size of the array is small enough this will create a legal typedef named dummy that we don't actually use.

    If the size is too big then the typedef is illegal an the compiler should give an error.

    Some compilers/mode allow zero length arrays, but I haven't met one that allows -1 length arrays.

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  • 0 Arm Employee Badge

    Maybe something like this is what you want:

    ... some declaration of my_array ...

#define MAX_SIZE 5000 /* bytes, for example */

typedef int dummy[sizeof(my_array) <= MAX_SIZE ? 1 : -1];

    If the size of the array is small enough this will create a legal typedef named dummy that we don't actually use.

    If the size is too big then the typedef is illegal an the compiler should give an error.

    Some compilers/mode allow zero length arrays, but I haven't met one that allows -1 length arrays.

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