_STATIC_ASSERT Macro
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_STATIC_ASSERT Macro

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

_STATIC_ASSERT(
    booleanExpression
);

booleanExpression

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

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.

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 will not 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));
}

Macro

Required header

_STATIC_ASSERT

<crtdbg.h>

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