Page 58 - C-Language

r = length2 (b, COUNT);
printf ("r = %i\n", r);
return 0;
}

Simple Assertion

An assertion is a statement used to assert that a fact must be true when that line of code is
reached. Assertions are useful for ensuring that expected conditions are met. When the condition
passed to an assertion is true, there is no action. The behavior on false conditions depends on
compiler flags. When assertions are enabled, a false input causes an immediate program halt.
When they are disabled, no action is taken. It is common practice to enable assertions in internal
and debug builds, and disable them in release builds, though assertions are often enabled in
release. (Whether termination is better or worse than errors depends on the program.) Assertions
should be used only to catch internal programming errors, which usually means being passed bad
parameters.

#include <stdio.h>
/* Uncomment to disable `assert()` */
/* #define NDEBUG */
#include <assert.h>

int main(void)
{
int x = -1;
assert(x >= 0);

printf("x = %d\n", x);
return 0;
}

Possible output with NDEBUG undefined:

a.out: main.c:9: main: Assertion `x >= 0' failed.

Possible output with NDEBUG defined:

x = -1

It's good practice to define NDEBUG globally, so that you can easily compile your code with all
assertions either on or off. An easy way to do this is define NDEBUG as an option to the compiler, or
define it in a shared configuration header (e.g. config.h).

Static Assertion

C11

Static assertions are used to check if a condition is true when the code is compiled. If it isn't, the
compiler is required to issue an error message and stop the compiling process.

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