NAME     
| assert – check program invariants | 
SYNOPSIS     
| #include <u.h> #include <libc.h> #define assert(cond) if(cond);else _assert("cond") 
    void _assert(char* cond) | 
DESCRIPTION     
| Assert is a preprocessor macro that (via _assert) prints a message
    and calls abort when cond is false. | 
SOURCE     
| /sys/src/libc/port/_assert.c |