The classic C macro # define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) has a nasty…

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The classic C macro # define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) has a nasty problem. pass it a pointer instead of an actual array, and it can silently return the wrong element count. older Linux kernels had a clever solution. They used a compiler type check inside a negative-width bit-field: int:(-!!(e)). Pass a real array, and the check adds zero. Pass a pointer, and the bit-field width becomes negative, causing compilation to fail. Here's the macro chain used in older Linux kernels:

Posted by Arika (9k followers) 2 days ago · 170 likes · 9.5k views · view the original post on X. Kept by the Dev Radar as Languages & runtimes.

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