Are your recompiles too fast? Just use DELAY(N)!

From: vesa_karvonen (vesa_karvonen_at_[hidden])
Date: 2002-01-24 11:06:29

I just committed a fun preprocessor example into the CVS.

The DELAY() macro implemented in the example source takes exponential 
time to expand into nothing. For instance, on the 800MHz PIII I use 
at the office, it takes roughly 4 seconds to compile delay.cpp like 
this on the MSVC++ compiler:

cl -Zs -nologo -I../../.. -DDELAY_MAX=15 delay.cpp

The maximum argument to delay is 50. This means that if I use the 
command:

cl -Zs -nologo -I../../.. -DDELAY_MAX=50 delay.cpp

It takes roughly 4000 years to complete.

As an interesting technical detail, DELAY() takes a constant amount 
of memory to compile. Similar delaying tricks can be done using 
template metaprogramming, but they do not work very well, because 
template instantiation takes a lot of memory, so eventually the 
computer runs out of memory.