static-assert-macro.md

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Learn more about: _STATIC_ASSERT Macro	_STATIC_ASSERT Macro	11/04/2016	msvcrt.dll msvcr80.dll msvcr90.dll msvcr100.dll msvcr100_clr0400.dll msvcr110.dll msvcr110_clr0400.dll msvcr120.dll msvcr120_clr0400.dll ucrtbase.dll	DLLExport	apiref	_STATIC_ASSERT	_STATIC_ASSERT macro	89b0350c-2c2f-4be6-9786-8b1f0780a5da

_STATIC_ASSERT macro

Evaluate an expression at compile time and generate an error when the result is FALSE.

Syntax

_STATIC_ASSERT(
    booleanExpression
);

Parameters

booleanExpression
Expression (including pointers) that evaluates to nonzero (TRUE) or 0 (FALSE).

Remarks

This macro resembles the _ASSERT and _ASSERTE macros, except that booleanExpression is evaluated at compile time instead of at runtime. If booleanExpression evaluates to FALSE (0), Compiler Error C2466 is generated.

Example

In this example, we check whether the sizeof an int is larger than or equal to 2 bytes and whether the sizeof a long is 1 byte. The program won't compile and it will generate Compiler Error C2466 because a long is larger than 1 byte.

// crt__static_assert.c

#include <crtdbg.h>
#include <stdio.h>

_STATIC_ASSERT(sizeof(int) >= 2);
_STATIC_ASSERT(sizeof(long) == 1);  // C2466

int main()
{
    printf("I am sure that sizeof(int) will be >= 2: %d\n",
        sizeof(int));
    printf("I am not so sure that sizeof(long) == 1: %d\n",
        sizeof(long));
}

Requirements

Macro	Required header
_STATIC_ASSERT	<crtdbg.h>

See also

Alphabetical function reference
_ASSERT, _ASSERTE, _ASSERT_EXPR macros