Preprocessor macros used in cpp file gets undef'ed in the header file

What steps will reproduce the problem?
1.Enable -Wundef compiler flag
2.Build
3.Warning in btDbvt.cpp, saying that DBVT_IMPL_GENERIC, DBVT_IMPL_SSE and 
DBVT_MERGE_IMPL are not defined and are defaulting to zero. This is because 
these defines are undef'ed in the end of btDbvt.h.
4.This results in the code inside e.g. #if (DBVT_MERGE_IMPL==DBVT_IMPL_SSE) in 
btDbvt.cpp is being compiled regardless. This has effect when building for Arm 
(iPhone). Exactly what the impact of this is, I don't know.

What version of the product are you using? On what operating system?
2.81, on OSX and iOS

Original issue reported on code.google.com by andr...@illusionlabs.se on 15 Nov 2013 at 8:24

KingOfDaAwesome / bullet

Preprocessor macros used in cpp file gets undef'ed in the header file #768