g->GCthreshold overflow, possible bug?

["Cheng, Long" <long.x.cheng@...>]

hi group:
Today I noticed some strange behavior in my lua application:
My application disables lua autogc and manually calls lua_gc(LUA_GCSTEP) 
regularly. When memory usage exceeds 2G, each call to lua_gc(LUA_GCSTEP) 
becomes a full gc cycle (retval = 1).
I managed to track down the cause of this problem to the following line 
in lgc.c:

#define setthreshold(g)  (g->GCthreshold = (g->estimate/100) * g->gcpause)

When g->estimate exceeds 2G and gcpause remains its default value 200, 
GCthreshold will overflow uint32 range.
I made the following fix and testing shows it is good:

#define setthreshold(g)  (g->GCthreshold = ((long long)g->estimate/100) 
* (long long)g->gcpause > MAX_LUMEM ? MAX_LUMEM : (g->estimate/100 * 
g->gcpause) )


Is this a bug? Is there any known solution for this?
The lua version I used is luajit 1.1.5/lua 5.1.4 and I can not switch to 5.2

Thanks


Regards
Long