C11 & C17 Modern Features

The C language evolves. Modern standards add safety, concurrency, and convenience.

Feature	Header	Usage
_Static_assert	<assert.h>	Compile‑time assertion (_Static_assert(sizeof(int)==4, "int not 4 bytes");).
Anonymous structs/unions	—	Allows nested structs without a name (useful for low‑level memory mapping).
_Thread_local	<threads.h>	Declares thread‑local storage (_Thread_local int counter;).
alignas / alignof	<stdalign.h>	Controls/alters alignment constraints.
static_assert (macro)	<assert.h>	Same as _Static_assert but macro for pre‑C11 compilers.
generic selections	<tgmath.h>	Type‑generic macros (generic_max(1, 2.5) resolves to proper overload).
atomic types	<stdatomic.h>	Lock‑free atomic operations (atomic_int a; atomic_fetch_add(&a, 1);).
aligned_alloc	<stdlib.h>	Allocate memory with specific alignment.

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📚 Example: Compile‑time Size Check

#include <assert.h>
_Static_assert(sizeof(void*) == 8, "Pointer size is not 8 bytes");