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8.1 alignof and alignas ¶

Gnulib module: alignasof

The alignasof module arranges for alignas and alignof to be more like standard C.

Portability problems fixed by Gnulib:

• On pre-C23 platforms, <stdalign.h> must be included before using alignas or alignof. See stdalign.h.

Portability problems not fixed by Gnulib:

• The set of alignments supported by alignas is implementation dependent, and implementations need not support alignments greater than alignof (max_align_t).
• Some older platforms do not support alignas. To test this, use the alignasof module along with the #if conditional (defined alignas || defined __alignas_is_defined || 202311 <= __STDC_VERSION__ || 201103 <= __cplusplus). Platforms where alignas does not work include: IBM XL C for AIX V16.1.
• On some platforms, the argument of alignas must be an integer constant like ‘8’, instead of an integer constant expression like ‘4 + 4’ that evaluates to 8: GCC 4.9.
• On pre-C23 platforms, alignas and alignof are macros.