ciabatta/docs/assert.md

assert.h - debug assertions

Macro definitions:

• assert(expr)
• static_assert

assert

Assert a given condition is true, otherwise abort execution of a program.

The macro checks whether expr is true, and if not, prints the diagnostic information and then aborts execution in a way equivalent to calling abort() function (See SIGABRT).

If _DEBUG macro is defined, assert does not print a diagnostic message, and instead simply causes a debug break.

If NDEBUG macro is defined assert expands to an empty statement. If both NDEBUG and _DEBUG are defined, then _DEBUG macro is ignored.

#if defined(NDEBUG)
    #define assert(expr) ((void)0)
#elif defined(`_DEBUG`)
    #define assert(expr) /* debug break */
#else
    #define assert(expr) /* print diagnostic, then abort */
#endif

Example

// Uncomment to disable assert
//#define NDEBUG
#include <assert.h>

int factorial(int n) {
    assert(n >= 0);
    if(n == 0) return 1;
    return n*factorial(n-1);
}

int main() {
    printf("Factorial of %d is %d\n", 10, factorial(10));
    printf("Factorial of %d is %d\n", -1, factorial(-1));
    return 0;
}

The first function would print 3628800, the second would trigger an assert. Output:

Factorial of 10 is 3628800
Assertion failed: n >= 0
  Function: factorial
  File: test\test_assert.c
  Line: 4
Trace:
  4: factorial
  3: main
  2: mainCRTStartup
  1: BaseThreadInitThunk
  0: RtlUserThreadStart

static_assert

Keyword macro that expands to C11 keyword _Static_assert.

#define static_assert _Static_assert