- Add -DNDEBUG to the compiler flags when mode!=debug.
 - Prevent assert() from compiling out in kernel when mode=release

Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>

gcc recommends -Og for debugging; follow its advice.

Signed-off-by: Avi Kivity <avi@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>

the conf-logger_debug option control whether tprintf_d (verbose debug
logging) is enabled at all, if it is set to 0 then tprintf_d is
implemented as do{}while(0)

This allocator works by giving each allocation its own virtual address
range which is not reused for later allocations.  After a free(), the
range is made inaccessible, forever, so use-after-free will result in a
page fault.

Sub-page overruns are also detected by filling unallocated space with a
pattern, and checking whether the pattern has been altered during free().

Now that the context switch code is red zone safe, allow the compiler
to use it.

Causes an early failure for some reason.  Disable until root cause is found.

 'make conf-preempt=0'

->

 'g++ ... -DCONF_preempt=0'

Use #if, not #ifdef in sources to reduce errors due to misspellings.

Easier to manage different configurations this way.